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Ik- EDGEWOOD 


CHEMICAL BIOLOGICAL CENTER 

U.S. ARMY RESEARCH, DEVELOPMENT AND ENGINEERING COMMAND 


ECBC-TR-659 


EVALUATION OF MOF-74, MOF-177, and ZIF-8 
FOR THE REMOVAL OF TOXIC INDUSTRIAL CHEMICALS 


Gregory W. Peterson 
John Mahle 
Alex Balboa 
George Wagner 
Tara Sewell 
Christopher J. Karwacki 

RESEARCH AND TECHNOLOGY DIRECTORATE 


November 2008 


Approved for public release; 
distribution is unlimited. 


20081230008 



ABERDEEN PROVING GROUND, MD 21010-5424 










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1. REPORT DATE (DD-MM-YYYY) 2. REPORT TYPE 

XX-11-2008 Final 

3. DATES COVERED (From - To) 

Feb 2008 - Mar 2008 

4. TITLE AND SUBTITLE 

Evaluation of MOF-74, MOF-177, and Z1F-8 for the Removal of Toxic 
Industrial Chemicals 

5a. CONTRACT NUMBER 

5b. GRANT NUMBER 

5c. PROGRAM ELEMENT NUMBER 

6. AUTHOR(S) 

Peterson, Gregory W.; Mahle, John; Balboa, Alex; Wagner, George; 

Sewell, Tara; and Karwacki, Christopher J. 

5d. PROJECT NUMBER 

BA07PROI04 

5e. TASK NUMBER 

5f. WORK UNIT NUMBER 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

DIR. ECBC, AMSRD-ECB-RT-PF, APG, MD 21010-5424 

8. PERFORMING ORGANIZATION REPORT 
NUMBER 

ECBC-TR-659 

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Defense Threat Reduction Agency, 8725 John J. Kingman Road, 

Room 3226, Fort Belvoir, VA 22060-6201 

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DTRA 

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NUMBER(S) 


12. DISTRIBUTION / AVAILABILITY STATEMENT 

Approved for public release; distribution is unlimited. 


13 SUPPLEMENTARY NOTES 


14. ABSTRACT 

Current technology-based efforts are focusing on a nanotechnology approach to sorbent development for air 
purification applications. Metal-organic frameworks (MOFs) and zeohtic imidazolate frameworks (ZIFs) are two 
novel classes of materials that allow for specific functionalities to be designed directly into a porous framework. 
This report is the second in a series of summary reports based on the evaluation of samples from the University of 
California, Los Angeles. The samples evaluated in this report are a continuation of a baseline series of materials 
aimed at collecting design rules for future materials; results from this and the previous report will be used to create 
a second-generation of reactive MOFs and ZIFs for air purification applications. Testing of the novel materials 
included nitrogen isotherm data, water, and chloroethane adsorption equilibria, and ammonia, cyanogen chloride 


and sulfur dioxide breakthrough data. 

15. SUBJECT TERMS 

Air purification 
Nanotechnology 
Breakthrough testing 

Metal-organic frameworks 
Porous framework 

MOFs 

Isotherm 

Sorbent development 
Adsorption equilibria 


16. SECURITY CLASSIFICATION OF: 

17. LIMITATION OF 

18. NUMBER OF 

19a. NAME OF RESPONSIBLE PERSON 




ABSTRACT 

PAGES 

Sandra J. Johnson 

a. REPORT 

b. ABSTRACT 

c. THIS PAGE 


38 

19b. TELEPHONE NUMBER (include area 
code) 

U 

U 

U 

U 

(410) 436-2914 


Standard Form 298 (Rev. 8-98) 

Prescribed by ANSI Std. Z39.18 
































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11 


PREFACE 


The work described in this report was authorized under Project No. 
BA07PR0104. This work was started in Feburary 2008 and completed in March 2008. 

The use of either trade or manufacturers’ names in this report does not constitute 
an official endorsement of any commercial products. This report may not be cited for the 
purposes of advertisement. 

This report has been approved for public release. Registered users should request 
additional copies from the Defense Technical Information Center; unregistered users should 
direct such requests to the National Technical Information Service. 


Acknowledgments 

The authors thank Oniar Yaghi and David Brit (University of California, Los 
Angeles) for synthesizing the Metal-organic and zeolitic imidazolate framework samples. David 
Tevault (U.S. Army Edgewood Chemical Biological Center) and Paulette Jones (Science 
Applications International Corporation) are thanked for their analyses and review of the data and 
report. 









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IV 


CONTENTS 


1. INTRODUCTION.1 

2. EXPERIMENTAL PROCESS.1 

2.1 Samples Evaluated.1 

2.2 Testing Protocol.3 

3. RESULTS AND DISCUSSION.7 

3.1 Packing Density.7 

3.2 Nitrogen Isotherm.7 

3.3 Chloroethane Adsorption Equilibria.10 

3.4 Water AE.12 

3.5 Ammonia Micro-Breakthrough.13 

3.6 CK Micro-Breakthrough.15 

3.7 Sulfur Dioxide Micro-Breakthrough.18 

4. SUMMARY.19 

LITERATURE CITED.25 

APPENDIXES 

A: PREVIOUS MOFS EVALUATED.AI 

B: MOF SYNTHESIS TECHNIQUES.B1 


v 





















FIGURES 


1. Samples Evaluated.2 

2. Adsorption Equilibrium System Schematic.4 

3. Water Isotherm System.5 

4. Rapid Nanoporous Adsorbent Screening System.6 

5. Nitrogen Isotherm Plot.8 

6. Nitrogen Isotherm Log Plot.8 

7. Chloroethane AE at 25 °C-Volume Basis.11 

8. Water AE at 25 °C.12 

9. Ammonia Breakthrough Curves under Dry Conditions.13 

10. Ammonia Breakthrough Curv es under Humid Conditions.14 

11. CK Breakthrough Curves under Low RH Conditions.16 

12. CK Breakthrough Curves under Humid Conditions.17 

13. SO 2 Breakthrough Curves under Dry Conditions.18 

14. SO; Breakthrough Curves under Humid Conditions.19 

15. Design Strategy for Unsaturated Metal MOFs.22 

16. Design Strategy for IRMOFs.23 


vi 


















TABLES 


Packing Density of MOFs. 

Fit Parameters for Calculated BET. 

Calculated BET Capacity and Porosity of MOFs. 

Comparison of ECBC and UCLA Calculated BET Capacity. 

Volume of Nitrogen Adsorbed on Selected Materials-Mass Basis. 

Volume of Nitrogen Adsorbed on Selected Materials-Volume Basis 
Chloroethane Equilibrium Loading of Evaluated Samples at 25 °C.... 

Moisture Loading of Sorbents at 25 °C. 

Ammonia Dynamic Capacity of Sorbents. 

CK Dynamic Capacity of Sorbents. 

SO: Dynamic Capacity of Sorbents. 

Comparison of Physical Properties of Sorbents Studied. 

Comparison of Removal Capacities of Sorbents Studied. 


..7 

..9 

..9 

10 

10 

10 

11 

13 

15 

17 

20 

20 

21 




















Blank 


EVALUATION OF MOF-74, MOF-177, AND ZIF-8 FOR THE REMOVAL 
OF TOXIC INDUSTRIAL CHEMICALS 


1. INTRODUCTION 

In February 2008, Professor Omar Yaghi’s group at the University of California, 
Los Angeles (UCLA), provided two metal-organic framework (MOF) samples and one zeolitic 
imidazolate framework (Z,1F) to the U.S. Army Edgewood Chemical Biological Center (ECBC) 
for evaluation. Metal-organic frameworks and ZIFs have shown promise for incorporation into 
air purification technologies due to their ability to modify pore size and functionality on a 
molecular level. The objective of this evaluation was to assess the physical properties as well as 
the adsorptive and reactive capabilities of the MOF and Z1F samples in order to provide 
feedback to Prof. Yaghi’s group for the development of new materials. This report provides a 
summary of the evaluation as well as suggestions for improved MOF/Z1F performance. 

The development and evaluation of the MOF and ZIF samples summarized in this 
report are part of a larger Defense Threat Reduction Agency funded effort to develop novel, 
nanoscale porous materials for use as sorbents in air purification applications. The objective of 
this effort is to evaluate the performance characteristics of novel sorbents against a variety of 
toxic industrial chemicals (TICs) and chemical warfare agents (CWAs) with an emphasis on 
highly reactive materials that possess broad spectrum filtration capabilities. The goal is to 
develop materials capable of providing better/broader protection than our current filtration 
material, ASZM-TEDA, or to complement its filtration properties, possibly leading to composite 
filters with tailorable performance. If successful, this approach should enable the development of 
materials and filter designs to purify air via first principles. 

This report is the second in a series of summary reports based on the evaluation of 
samples from UCLA. The first report (Peterson et al., 2008) focused on IRMOF-1 (MOF-5), 
IRMOF-3, IRMOF-62, and MOF-199 and provided recommendations for future material 
syntheses. Structures and formulas are provided in Appendix A. The samples evaluated in this 
report are the continuation of a baseline series of materials aimed at collecting design rules for 
future materials; results from this report and the previous report will be used to create a second- 
generation of reactive MOFs and ZIFs for air purification applications. 


2. EXPERIMENTAL PROCESS 

2.1 Samples Evaluated 


The MOF and ZIF samples evaluated are illustrated in Figure 1. 





MOF-74 

Zn 3 [(0) 3 (C0 2 )3] 



PICTURE 



STRUCTURE 



METAL CENTER 
(Wong-Foy et al) 


OH 

O 2 C—^ —C0 2 

ho / 

DHBDC 

LINKER 

(Rosi el al) 


MOF-177 




BTB 


PICTURE 


■ 



PICTURE 


STRUCTURE METAL CENTER 

(Rowsell el al) 


ZIF-8: Sodalite Topology 

ZnCsN^io 



STRUCTURE TOPOLOGY 

(Park et al) 


LINKER 

(Kim et al.) 



LINKER 


Figure 1. Samples Evaluated 


2 






MOF-74 (ECBC ID# 043-08) is a mctal-organic framework that has 
3-dimensional rod metal oxides, which form a helical Zn-O-C structure, and 1-dimensional 
hexagonal channels (Rosi et al., 2005: Rowsell and Yaghi 2006; Liang and Shimizu, 2007). The 
zinc used in this structure has a coordination number of 6, but is only bonded to 5 oxygen atoms, 
leaving a highly reactive site. The material received at ECBC was in the form of a yellow-orange 
powder. 


MOF-177 (ECBC lD#044-08) is a metal-organic framework with tetrahedral 
basic zinc acetate clusters and 1,3,5-benzenetribenzoate (BTB) linkers (Wong-Foy et al., 2006; 
Li and Yang, 2007) that form a 3-dimensional pore network. The material received at ECBC 
was in the form of white, flaky, rod-like granules. 

Z1F-8 (ECBC lD#024-08) is a zeolitic imidazolate framework that mimics the 
sodalite topology. The structure consists of Zn ions and 2-methylimidazolate in a 1:2 ratio. 
The empirical formula reported by UCLA is ZnCgN^io. The material received at ECBC was in 
the form of a white powder. 

Synthesis procedures for the MOFs studied are summarized in Appendix B (Li et 
al., 1999; Chae et al., 2004; Rowsell and Yaghi, 2006; Park et al., 2006). 


2.2 Testing Protocol 

The MOFs were evaluated by collecting the following data: nitrogen isotherm, 
packing density, temperature and moisture stability, nitrogen and chloroethane adsorption 
equilibria, and micro-breakthrough testing. 

The packing density of each sample was determined in order to summarize data 
on both a mass and volume basis. Samples were placed in a 10-mm outside diameter glass tube. 
Dry air was passed through the samples for approximately 4 hr and then weighed. The resulting 
weight and volume were used to calculate the packing density. 

Nitrogen isotherm data were collected with a Quantachrome Autosorb Automated 
Gas Sorption System. Approximately 20 mg of each MOF were used for the analysis. Samples 
were outgassed at a temperature of 150 °C for at least 8 hr prior to data measurement. Nitrogen 
isotherm data were used to estimate the surface area, pore volume, and average pore size. 

Chloroethane (CE) adsorption equilibrium (AE) data were collected at 25 °C for 
the MOF and baseline samples on the system illustrated in Figure 2. The equilibrium system 
utilizes a Fourier Transform Infrared (FT1R) spectrometer to determine the CE vapor phase 
concentration, and by inference, CE capacity at different relative pressures. Data are collected 
based on the vapor concentration difference pre- and post-chcmical challenge to a pre-weighed 
adsorbent and measured volume (i.e., volumetric). Calibrated sample loops provide chemical to 
the volumetric system in precise quantities. The FTIR spectrometer measures the vapor 
concentration by partial least squares fit of single and multicomponent chemical vapor 
concentrations. 


3 







Figure 2. Adsorption Equilibrium System Schematic 


Water isotherms were collected on the MOFs and ASZM-TEDA at 25 °C. Water 
was delivered from a saturator cell to a temperature-controlled microbalance containing the 
sorbent to be evaluated. The concentration of moisture in the air, or relative humidity (RH), was 
systematically increased (or decreased) by changing the temperature of the saturator cell. By 
measuring the change in weight, the amount of water adsorbed on the material was calculated. A 
system schematic is illustrated in Figure 3. 


4 














































Microha lance 



A 



Figure 3. Water Isotherm System 


Samples were evaluated for ammonia, cyanogen chloride (CK) and sulfur dioxide 
capacity using micro-breakthrough systems. A specific amount of chemical was injected into a 
ballast and subsequently pressurized; this chemical mixture was then mixed with an air stream 
containing the required moisture content (from a temperature-controlled saturator cell) in order 
to achieve a predetermined concentration. The completely mixed stream then passed through a 
sorbent bed submerged in a temperature-controlled water bath. Approximately 20 mg of each 
sample were tested under dry and humid conditions. The effluent stream then passed through a 
continuously operating gas chromatograph. A system schematic is shown in Figure 4 


5 



















































Rapid Nanoporous Adsorbent Screening System 

(RNASS) 



Figure 4. Rapid Nanoporous Adsorbent Screening System 


Approximately 50 mm of sorbent were evaluated using an ammonia challenge at 
a feed concentration of 800 mg/m' in air, a bed depth of 4 mm, a flow rate of 20 mL/min 
(referenced to 25 °C) through a 4 mm tube, and RH of approximately 0% (approximately -40 °C 
dew point). The residence time (bed volume divided by the flow rate) was approximately 0.15 s. 
In all cases, sorbents were pre-equilibrated for 1 hr at the same RH as the test. The effluent 
concentrations were monitored using a photoionization detector (PID). 

Approximately 50 mm' of sorbent were evaluated using a cyanogen chloride 
(C1CN or CK) challenge at a feed concentration of 4,000 mg/m in air, a flow rate of 20 mL/min 
(airflow velocity of approximately 3 cm/s) referenced to 25 °C, a temperature of 20 °C, and 
relative humidities of approximately 0% and 80%. In all cases, sorbents were pre-equilibrated for 
approximately 1 hr at the same RH as the test. The effluent concentrations were monitored with a 
HP5890 Series II Gas Chromatograph equipped with a flame ionization detector (GC/FID). 

Approximately 50 mm' of sorbent were evaluated with sulfur dioxide at a feed 
concentration of 1,000 mg/m', a flow rate of 20 mL/min (airflow velocity of approximately 
3 cm/s) referenced to 25 °C, a temperature of 20 °C, and RHs of approximately 
0 and 80%. In all cases, sorbents were pre-equilibrated for 1 hr at the same RH as the test. The 
concentration eluting through the sorbent was monitored with a HP5890 Series II Gas 
Chromatograph equipped flame photometric detector (GC/FPD). 


6 






















































3. 


RESULTS AND DISCUSSION 


3.1 Packing Density 

The packing density of each sample was calculated in order to summarize data on 
both a mass and volume basis. Although data are typically reported on a mass basis, filters are 
designed on a volume basis. The packing density was determined by placing each material in a 
10-mm OD glass tube, passing dry air through each sample for approximately 4 hr and then 
dividing the dry weight by the volume of the material. Packing density measurements are 
summarized in Table 1. 


Table 1. Packing Density of MOFs 


Sample 

Approximate Mesh 

Packing Density 

MOF-74 

Powder, <70 

0.47 g/cc 

MOF-177 

Powder, <70 

0.23 g/cc 

ZIF-8 

Powder, <70 

0.57 g/cc 

ASZM-TEDA 

12x30 

0.61 g/cc 


*An actual sieve analysis was not conducted particle mesh was estimated 


All MOF samples received have a significantly lower packing density than 
ASZM-TEDA. This may become an issue if/when MOFs are used in a filter configuration, as all 
filters are filled by volume and not mass. Therefore, all properties are reported on both a mass 
and a volume basis. 


3.2 Nitrogen Isotherm 

Nitrogen isotherm data were collected with a Quantachrome Autosorb Automated 
Gas Sorption System. Approximately 50 mg of each MOF was used for the analysis. Samples 
were outgassed at a temperature of 150 °C for at least 8 hr. Nitrogen isotherm data were 
collected over six orders of magnitude of relative pressure and then used to estimate the surface 
area, pore volume and average pore size of MOF samples. Data are illustrated in Figures 5 and 6. 


7 


















1200 



□ .O^OOHD 


□ Q 0 GD-Q O □ 


—O — MOF-74 
□ MOF-177 

—A—2IF-8 

ASZM-TEDA 

Ar-A A A A A - A A A A A ArA A A A A A 


0.2 0.4 0.6 

Relative Pressure (p/psat) 

Figure 5. Nitrogen Isotherm Plot 


0.8 


1.0 


o> 

CL 

h 

if) 

<§> 

-Q 

k- 

O 

</> 

"D 

< 

0) 

E 

D 

O 

> 

CN 


o 

MOF-74 

□ 

MOF-177 

A 

ZIF-8 

O 

t—l\ 

ASZM-TEDA 


□ 


cfp&n 


1.E-05 1.E-04 1.E-03 1.E-Q2 

Relative Pressure (p/psat) 

Figure 6. Nitrogen Isotherm Log Plot 


1.E-01 



1.E+00 


All of the samples studied exhibit higher Type I plateaus than ASZM-TEDA, 
indicating higher BET capacity values and higher nitrogen uptake at higher relative pressures. At 
low relative pressures, however, only MOF-74 has better nitrogen adsorption properties than 
ASZM-TEDA, likely due to the higher energy potential created from the open zinc sites. 
MOF-177 and ZIF-8 have much lower nitrogen adsorption volumes at low relative pressures 
than either ASZM-TEDA or MOF-74. In MOF-177, this is likely due to the relatively large 


8 

























distances between metal clusters resulting in low adsorption potentials. However, at higher 
relative pressures, the very open structure results in very large quantities of nitrogen adsorption 
compared to the other samples as well as an extremely high BET capacity. In Z1F-8, there is 
almost no nitrogen adsorption at low relative pressures, possibly due to exclusion from the small 
pores as well as a lack of adsorption potential. At high relative pressures, however, nitrogen 
adsorption is much higher than the baseline ASZM-TEDA sample due to the large pore volumes 
from the supercages. 

From the nitrogen isotherm plots, values were calculated for l/[W((Po/P)-l)] and 
plotted against relative pressure in order to calculate BET surface area. Fit parameters are 
summarized in Table 2. 


Table 2. Fit Parameters for Calculated BET 


Sample 

Slope 

Y-lntercept 

R 2 

C 

MOF-74 

3.517 

0.0008189 

0.999999 

4,295 

MOF-177 

0.855 

0.001442 

0.999839 

594.1 

Z1F-8 

2.177 

0.001545 

0.999034 

1,411 

ASZM-TEDA 

4.224 

0.0104300 

0.999971 

406.1 


Nitrogen isotherm data were used to calculate the BET capacity, total pore 
volume, and average pore size. The term BET capacity, and not surface area, is used for reasons 
described in the previous Tech Report as well as by Walton and Snurr and Rouquerol et al. The 
packing density was used to calculate the values on both a mass and volume basis. Tabic 3 
summarizes the calculated values. 


Table 3. Calculated BET Capacity and Porosity of MOFs 


Sample 

BET Capacity 

Pore Volume 

Pore 

Width (A)* 

Pore Aperture 

(A)* 

nT/g- 

adsorbent 

m 2 /cm- 

adsorbent 

enr-N 2 /g- 
adsorbent 

cm -N 2 /cm^- 

adsorbeni 

MOF-74 

990 

465 

0.48 

0.23 

10.8 

10.8 

MOF-177 

4,065 

935 

1.73 

0.40 

11.8 

9.6 

ZIF-8 

1,600 

910 

0.65 

0.37 

11.6 

3.4 

ASZM-TEDA 

820 

500 

0.46 

0.28 

Heterogeneous* * 


*Received from UCI.A, calculated based on geometry of unit cell 
**Heterogeneous distribution of micropores, mesopores, and macropores 


According to the values summarized in Table 3, MOF-74 has similar properties to 
ASZM-TEDA, with a slightly higher BET capacity and pore volume on a mass basis but a 
slightly lower BET capacity and pore volume on a volume basis. MOF-177 has an extremely 
high BET capacity and a wide-open pore network. Z1F-8 has a higher BET capacity and pore 
volume than ASZM-TEDA; however, the pore width is small and may pose a mass transfer 
problem in dynamic breakthrough testing. 


9 



























Professor Yaghi’s group also performed BET measurements on the samples sent 
to ECBC; the results are summarized in Table 4. Tables 5 and 6 summarize the amount of 
nitrogen adsorbed at various relative pressures. 


Table 4. Comparison of ECBC and UCLA Calculated BET Capacity 


Sample 

ECBC BET 
Capacity 

UCLA BET 
Capacity 

% Difference 

MOF-74 

990 rrf/g 

1,130 m 2 /g 

+ 14.1% 

MOF-177 

4,065 m 2 /g 

4,500 rrf/g 

+ 10.7% 

Z1F-8 

1,600 m 2 /g 

1,210 m'/g 

- 24.4% 


Table 5. Volume of Nitrogen Adsorbed on Selected Materials-Mass Basis 


Samples 

-i- 

Volume N 2 Adsorbed (cm -STP/g-sor 

bent) 

P/P 0 = 0.001 

P/Po = 0.01 

NH 

o 

II 

o 

On 

fiu 

P/Po = 0.3 

MOF-74 

200 

225 

244 

260 

MOF-177 

139 

607 

981 

1,032 

ZIF-8 

217 

367 

375 

386 

ASZM-TEDA 

128 

161 

205 

233 


Table 6. Volume of Nitrogen Adsorbed on Selected Materials-Volume Basis 


Samples 

Volume 

\ 2 Adsorbed (cm 3 -STP/cm 3 -sorbent) 

P/Po = 0.001 

P/P ft = 0.01 

P/P« = 0. 1 

P/P ft = 0. 3 

MOF-74 

94 

106 

115 

122 

MOF-177 

32 

140 

226 

237 

ZIF-8 

124 

209 

214 

220 

ASZM-TEDA 

78.1 

97.9 

125 

142 


3.3 Chloroethane Adsorption Equilibria (AE) 

Chloroethane AE were collected to assess the physical adsorption capacity of 
MOF samples for light chemicals. Chloroethane was chosen as one of the chemicals of interest 
due to its similar physical properties with CK, a chemical that is historically filtration-limiting on 
military air purification sorbents. Chloroethane and CK generally have similar physical 
adsorption behavior but dissimilar reactive behavior; thus, the potential to differentiate physical 
and reactive behavior exists. Adsorption Equilibria data for MOF and baseline samples are 
shown in Figure 7. 


10 






























0.1 


0.08 


—e—MOF-74 
—0— MOF-177 
— A —ZIF-8 

- ASZM-TEDA 


o 

o 

D) 


O) 

c 

■5 

n 

o 


0.06 

0.04 


0.02 



500 1000 1500 2000 

Partial Pressure (Pa) 

Chloroethane AE at 25 °C Volume Basis 


Figure 7. 


2500 


As compared to ASZM-TEDA, the MOF and Z1F samples have a lower 
chloroethane equilibrium loading over the relative pressure range studied. This was expected for 
MOF-177 and ZIF-8 as the nitrogen isotherms indicated weak physical adsorption at low relative 
pressures. The chloroethane capacity for MOF-74 was expected to be higher; however, initially, 
MOF-74 exhibits similar chloroethane adsorption to ASZM-TEDA, although above 
approximately 100 Pa, the chloroethane capacity drops off significantly from ASZM-TEDA. 
This behavior is strange as the surface area and pore volume of MOF-74 is similar to ASZM- 
TEDA. Perhaps, once a monolayer of chloroethane is formed on MOF-74, the adsorption 
potential drops significantly due to coverage and interaction with the zinc site. 


Chloroethane AE data were used to estimate the equilibrium loadings at 
three different concentrations (when applicable). Table 7 summarizes the results. 

Table 7. Chloroethane Equilibrium Loading (We) of Evaluated Samples at 25 °C 


Sample 

We @ 100 mg/m 3 
(~38 ppm; 

P/P„ = 2.4 x 10' 5 ) 

W E @ 1,000 mg/m 3 
(~380 ppm; 

P/P 0 = 2.4 x 10" 4 ) 

We @ 10,000 mg/m 3 
(~3,800 ppm; 

P/P« = 2.4 x 10' 3 ) 

g/g 

g/cc 

g/g 

, g/cc 

g/g 

g/cc 

MOF-74 

<0.016 

<0.077 

0.016 

0.077 

0.057 

0.027 

MOF-177 

< 0.0022 

< 0.0005 

0.0022 

0.0005 

0.047 

0.011 

ZIF-8 

< 0.0065 

< 0.0037 

<0.0065 

<0.0037 

0.0065 

0.0037 

ASZM-TEDA 

0.0039 

0.0024 

0.020 

0.012 

0.080 

0.049 


































Of the samples studied, MOF-74 has a significantly higher chloroethane 
equilibrium capacity at lower relative pressures, and a slightly higher CE capacity than MOF-177 
at moderate relative pressures. The unsaturated Zn ' site is likely responsible for this, providing 
higher adsorption potential. As relative pressures, increase, it is likely that MOF-177 will have 
higher CE capacities as the pore volume is over three times larger than that of MOF-74. ZIF-8 
has a very limited capacity, likely due to the small pore openings. 

3.4 Water AE 


Water AE were collected on MOF and ZIF samples using a Cahn balance to 
assess the moisture uptake at a full range of RH conditions. These data will be used to determine 
if the samples will preferentially adsorb water as opposed to toxic chemicals. AE data for MOF 
and baseline samples are shown in Figure 8. 



As expected, MOF-74 has significant moisture pickup at low RH conditions. This 
behavior is similar to Cu-BTC (MOF-199), which was evaluated in a previous technical report. 
The unsaturated metal site (in this case zinc, copper in the case of Cu-BTC) quickly coordinates 
with any water molecules present in the air stream. MOF-177 shows similar moisture pickup to 
ASZM-TEDA at low-to-mid RHs; however, ASZM-TEDA picks up significantly more water at 
high RH conditions. Both MOFs show significant hysteresis, something that we saw with other 
MOF samples as well. There are two likely explanations for the hysteresis. First, hysteresis may 
be a measure of pore interconnectivity - the more interconnected the pore network is, the more 
water acts as a bulk fluid as opposed to a sorbed phase. This translates to a different rate of 
evaporation (or desorption). The other possible cause of the hysteresis is that it takes a much 
longer time for a desorbing fluid to reach equilibrium as opposed to an adsorbing fluid; therefore, 
there may not have been enough elapsed time for the desorption branch to reach equilibrium. 
Table 8 summarizes the moisture loadings at three RH conditions. 


12 














Table 8. Moisture Loading of Sorbents at 25 °C 


Sample 

Water Load 

iing (g->vater/g-sorbent) 

15% RH 

50% RH 

80% RH 

ASZM-TEDA 

0.015 

0.088 

0.279 

MOF-74 

0.19 

0.24 

0.32 

MOF-177 

0.02 

0.10 

0.14 

ZIF-8 

<0.01 

<0.01 

<0.01 


3.5 Ammonia Micro-Breakthrough 

Ammonia micro-breakthrough testing was conducted on MOF samples under dry 
and humid conditions in order to assess ammonia reactive capacity and, more generally, the 
removal capacity of MOF samples for basic gases. ASZM-TEDA was run as a baseline sample 
and has a limited ammonia removal capacity. Approximately 50 ram of sorbent were tested at a 
feed concentration of 800 mg/m in air, a flow rate of 20 mL/min (referenced to 25 °C) through a 
4-mm tube, and RH conditions of approximately 0 and 80%. In all cases, sorbents were pre- 
cquilibrated for 1 hr at the same RH as the test. The feed and effluent concentrations were 
monitored with a P1D. Ammonia breakthrough curves under dry RH conditions are illustrated in 
Figure 9. 



Figure 9. Ammonia Breakthrough Curves under Dry (RH = 0%) Conditions 

[Ammonia] ~ 800 mg/m 


The two MOF samples show some ammonia removal capabilities, which are more 
extensive than ASZM-TEDA; in MOF-74, the ammonia is likely weakly coordinated to the Zn f ~ 
sites, which is supported by the slow initial desorption curve. MOF-177 does not provide an 
obvious reaction mechanism, but instead likely removes ammonia through initial physical 


13 
























adsorption followed by ammonia-ammonia interactions; again, this mechanism is supported by 
the desorption curve. ZIF-8 shows essentially no ammonia removal capabilities, likely due to the 
combination of very small pore openings and the lack of reactive sites. 

Ammonia breakthrough curves under humid (80% RH) conditions are illustrated 

in Figure 10. 



800 

700 

600 

500 

400 

300 

200 

100 

0 


0 50 100 150 200 

Time (min) 


Figure 10. Ammonia Breakthrough Curves under Humid (RH = 80%) Conditions 

[Ammonia] ~800 mg/m' 


As under dry conditions, both MOF samples show some ammonia removal 
capabilities. Although it was expected that the Zn 2 sites in MOF-74 would be coordinated and 
thus shielded by water, it is apparent that ammonia must be preferentially adsorbed; however, 
there is an initial hump in the breakthrough curve that could be attributed to ammonia-water 
competition. In MOF-177, it is likely that the extensive water uptake at high RH conditions 
helps with ammonia removal due to solubility effects, a similar phenomenon to the removal 
mechanism in ASZM-TEDA. Both MOFs and the ASZM-TEDA show significant desorption, 
indicating that ammonia removal is not permanent. ZIF-8 shows essentially no ammonia 
removal capacity, likely due to small pore openings and pre-adsorbed moisture blocking 
adsorption sites. 

Ammonia breakthrough data were used to calculate the dynamic capacity to the 
stoichiometric center of the breakthrough curve using eqs 1 and 2. The results are summarized 
in Table 9. 


14 




















Ct = t B *[Feed] 


(1) 


Where Ct 
tB 

[Feed] 


= mg-min/m 

= Breakthrough time [=] min 
Feed concentration [=] mg nr 


W r 


Ct * FR 
Mass 


Where W D = Dynamic capacity [=] g ammonia per g sorbent 
PR = Flow rate [=] mVmin 
Mass = Mass of sorbent [=] mg 


( 2 ) 


Table 9. Ammonia Dynamic Capacity of Sorbents 


Sample 

Sorbent 

Mass* 

(mg) 

Breakthrough 
Time to S.C. 

(min) 

VV D to 500 mg/m' 

Mass Basis 
(g/g) 

Volume Basis 

(g/cc)* 

MOF-74 (Dry) 

16.4 

103 

0.100 

0.047 

MOF-74 (Wet) 

13.5 

61 

0.073 

0.034 

MOF-177 (Dry) 

19.5 

41 

0.033 

0.008 

MOF-177 (Wet) 

16.9 

48 

0.045 

0.010 

ZIF-8 (Dry) 

24.9 

2 

0.001 

0 001 

Z1F-8 (Wet) 

18.0 

3 

0.002 

0.001 

ASZM-TEDA (Dry) 

30.0 

11 

0.025 

0.015 

ASZM-TEDA (Wet) 

25.0 

27 

0.031 

0.019 


*Dry basis - does not include mass of loaded water 


3.6 CK Micro-Breakthrough 

Cyanogen Chloride micro-breakthrough testing was conducted on MOF samples 
under dry and humid conditions to assess CK reactive capacity. In addition to information on CK 
removal capabilities, breakthrough curves should indicate the ability of MOFs to remove acid 
gases. ASZM-TEDA was run as a baseline sample and has a relatively high CK removal 
capacity. Approximately 50 mm' of sorbent were tested at a feed concentration of 4,000 mg/m', 
a flow rate of 20 mL/min (airflow velocity of approximately 3 cm/s) referenced to 25 °C, a 
temperature of 20 °C, and RHs of approximately 0 and 80%. In all cases, sorbents were pre¬ 
equilibrated for approximately 1 hr at the same RH as the test. The feed and effluent 
concentrations were monitored with an HP5890 Series II GC/FID. CK breakthrough curves for 
MOF and baseline samples under low-RH conditions are illustrated in Figure 11. 


15 




























Figure 11. CK Breakthrough Curves under Low RH Conditions 
[CK Challenge] = 4,000 mg/m 1 


Under low-RH conditions, ASZM-TEDA exhibits some uptake of CK. The 
shallow ASZM-TEDA breakthrough curve can be attributed to the relatively large particle size 
(-12-30 US mesh size or 1.7-0.6 mm, respectively) as compared to the MOF samples tested. 
Under the dry RH conditions, there may be some chemical reaction on ASZM-TEDA; however 
the primary mechanism for removal is likely physical adsorption, as the effluent concentration 
does not return to zero immediately following termination of CK challenge. MOF-74 has a 
similar breakthrough curve to ASZM-TEDA and removal may be due to some chemical reaction 
with the open Zn 2 site. This is supported by the CK effluent concentration quickly returning to 
the baseline after feed termination. MOF-177 and ZIF-8 show immediate CK breakthrough. In 
MOF-177, there is no reaction mechanism due to the shielded Zn sites which are spread really 
thin to promote significant adsorption. In ZIF-8, the combination of small pore openings and 
lack of reactive sites also results in essentially no CK capacity. 

Breakthrough curves for MOF and baseline samples collected under humid (80% 
RH) conditions are illustrated in Figure 12. 

Under humid conditions, ASZM-TEDA, which starts eluting on the far right of 
the graph, shows extensive CK capacity. This is consistent with previous CK studies as well as 
the proposed CK reaction mechanism on ASZM-TEDA, which involves hydrolysis. Under 
humid (80% RH) conditions, all MOF samples exhibit minimal CK removal capacity. Even 
MOF-74, which exhibits some removal capabilities under dry conditions, does not remove CK at 
high-RH conditions. The likely degradation mechanism is the hydration of the Zn active sites. 
Because CK is a high vapor pressure chemical (~ 1,200 torr at 25 °C), it can not compete with 
preadsorbed moisture for adsorption. 


16 
























Figure 12. CK Breakthrough Curves under Humid (RH = 80%) Conditions 

[CK Challenge] = 4,000 mg/m 1 


Breakthrough data on CK were used to calculate the dynamic capacity of the 
sorbents to the stoichiometric center using the same methodology as was used for ammonia. 
Results are summarized in Table 10. 


Table 10. CK Dynamic Capacity of Sorbents 


Sample 

Sorbent 

Mass* 

(mg) 

Breakthrough 
Time to S.C. 
(min) 

VV D to 2,000 mg/ni^ 

Mass Basis 

(s/s) 

V olume Basis * 

(g/cc) 

MOF-74 (Dry) 

10.1 

25 

0.197 

0.093 

MOF-74 (Wet) 

13.4 

0 

0.001 

0.001 

MOF-177 (Dry) 

10.2 

1 

0.009 

0.002 

MOF-177 (Wet) 

13.3 

0 

0.001 

<0.001 

ZIF-8 (Dry) 

21.2 

0 

<0.001 

<0.001 

ZIF-8 (Wet) 

26.6 

1 

0.002 

0.001 

ASZM-TEDA (Dry ) 

15.1 

26 

0.138 

0.084 

ASZM-TEDA (Wet) 

67.3 

143 

0.170 

0.104 


*Dry basis does not include mass of loaded water 


17 








































3.7 


Sulfur Dioxide Micro-Breakthrough 


Sulfur dioxide micro-breakthrough testing was conducted on MOF samples under 
dry and humid conditions in order to assess sulfur dioxide reactive capacity, and, more generally, 
the removal capacity of MOF samples for weak acid gases. The assumption is that if MOFs show 
removal mechanisms for weakly acidic gases, then strong acids should also be removed. ASZM- 
TEDA was tested as a baseline sample and has a relatively high sulfur dioxide removal capacity. 
Approximately 50 mm’ of sorbent were tested at a feed concentration of 1,000 mg/m\ a flow 
rate of 20 mL/min (airflow velocity of approximately 3 cm/s) referenced to 760 Torr and 25 °C, a 
temperature of 20 °C, and RHs of approximately 0 and 80%. In all cases, sorbents were pre¬ 
equilibrated for 1 hr at the same RH as the test. The concentration eluting through the sorbent 
was monitored with an FPD. Sulfur dioxide breakthrough curves for MOF and baseline samples 
are illustrated in Figures 13 and 14. 



- ASZM-T 

MOF-74 
-a— MOF-177 
—a — ZIF-8 



1,000 


900 


800 

?T 

700 

E 

600 

u> 

E 

500 

c7 

0 

400 

CO 

300 


200 


100 


20 30 40 

Time (min) 


Figure 13. SO: Breakthrough Curves under Dry (RH = 0%) Conditions 

[Challenge] = 1,000 mg/m 


Under dry RH conditions, both ASZM-TEDA and MOF-74 exhibit some SO 2 
removal; copper and zinc impregnants are responsible for SO 2 removal in ASZM-TEDA while it 
is likely that the unsaturated zinc site promotes a coordination reaction in MOF-74. In both 
cases, it is apparent from the desorption curves that both removal mechanisms are reversible, as a 
substantial amount of SO 2 elutes after feed termination. Neither MOF-177 nor ZIF-8 provides 
any substantial protection against SO 2 under dry RH conditions and the feed concentration is 
reached almost immediately for both samples. The covered zinc sites in MOF-177 are unable to 
provide any reaction mechanism for SO 2 , and it is possible that the pores in ZIF-8 are so small 
that mass transfer into the pores is inhibited. 


18 



















Figure 14 shows SO: breakthrough curves under high RH conditions. 



Time (min) 

Figure 14. SO: Breakthrough Curves under Flumid (RH = 80%) Conditions 

[Challenge] = 1,000 mg/m 3 

Under humid conditions, ASZM-TEDA and MOF-74 still provide SO: removal. 
Unlike dry RH conditions, however, these removal mechanisms are less reversible. The likely 
cause of this is a reaction between SO:, oxygen and water to form sulfuric acid, the sulfate of 
which may be more strongly and/or irreversibly chemisorbed on the metals in each sorbent. 
Although MOF-177 does provide better SO: removal under humid conditions as compared to dry- 
conditions, the capacity is significantly less than ASZM-TEDA. The performance of ZIF-8 is a 
surprise; although there is initial blow-by of the bed, possibly due to mass transfer limitations, 
ZIF-8 has a very high SO: capacity. This may be due to solution effects on the surface of ZIF-8. 
As more SO: goes into solution, the solution becomes more acidic and more favorable for 
additional SO: molecules. There may also be reaction within the supercages resulting in the 
formation of sulfuric acid, which is unable to desorb from the small pore apertures. 

SO: breakthrough data were used to calculate the dynamic capacity using the 
same methodology used for ammonia. The results are summarized in Table 11. 


4. SUMMARY 

Two MOFs and one ZIF were evaluated for nitrogen, chloroethane, and water 
adsorption as well as ammonia, CK, and sulfur dioxide breakthrough behavior to determine 
appropriate design rules and synthesize subsequent samples for air purification applications. 
Table 12 summarizes the MOFs evaluated, their distinguishing characteristics, and properties 
associated with their structures. 


19 





























Table 11. SO; Dynamic Capacity of Sorbents 


Sample 

Sorbent 

Mass* 

(mg) 

Breakthrough 
Time to S.C. 

(min) 

W D to 500 mg/m 3 

Mass Basis 

(g/g) 

Volume Basis * 

(g/cc) 

MOF-74 (Dry) 

15.3 

11 

0.014 

0.006 

MOF-74 (Wet) 

19.2 

9 

0.009 

0.004 

MOF-177 (Dry) 

15.3 

1 

0.001 

<0.001 

MOF-177 (Wet) 

14.6 

3 

0.004 

0.001 

ZIF-8 (Dry) 

18.6 

1 

0.001 

<0.001 

ZIF-8 (Wet) 

15.3 

138 

0.226 

0.129 

ASZM-TF.DA (Dry) 

25.7 

21 

0.025 

0.016 

ASZM-TEDA (Wet) 

56.1 

27 

0.105 

0.065 


*Dry basis - does not include mass of loaded water 


Table 12. Comparison of Physical Properties of Sorbents Studied 


Sample 

Distinguishing 

Characteristic 

BET 

Capacity 

Pore 

Volume 

Pore 

Width 

Pore 

Aperture 

h 2 o 

Capacity @ 
80% RH 

m 2 /g 

g/cc 

A 

A 

g/g 

MOF-5 

Baseline IRMOF 

3,290 

1.34 

11 . 0 & 

15.1 

7.8 

0.10 

IRMOF-3 

IRMOF with amino- 
functionalized BBC linker 

2,310 

0.99 

9.7 & 
15.1 

LAi 

VO 

1 

bo 

0.13 

IRMOF-62 

Interpenetrated IRMOF 

2,550 

1.09 

TBD 

TBD 

0.03 

MOF-199 

Unsaturated copper sites 

1,460 

0.68 

6.9, 

1 1.1 & 

13.2 

4.1 & 

6.9 

0.46 

MOF-74 

Unsaturated zinc sites 

990 

0.48 

10.8 

10.8 

0.32 

MOF-177 

Large linkers and very 
high surface area 

4,065 

1.73 

11.8 

9.6 

0.14 

ZIF-8 

Sodalite zeolite structure 

1,600 

0.65 

11.6 

3.4 

<0.01 

ASZM-T 

Activated carbon 

820 

0.46 

Heterogeneous 

0.28 


Table 13 summarizes the ammonia, CK and SO; breakthrough capacities for the 
MOFs evaluated in this as well as previous efforts. 


20 



































Table 13. Comparison of Removal Capacities of Sorbents Studied 


Sample 

Distinguishing 

Characteristic 

nh 3 

Capacity 

CK 

Capacity 

S0 2 

Capacity 

g/g 

g/g 

g/g 

MOF-5 (Dry) 

Baseline IRMOF 

0.02 

<0.01 

<0.01 

MOF-5 (Wet) 

0.19 

<0.01 

<0.01 






IRMOF-3 (Dry) 

IRMOF with amino- 
functionalized BBC linker 

0.17 

0.02 

<0.01 

IRMOF-3 (Wet) 

0.11 

<0.01 

0.01 






IRMOF-62 (Dry) 

Interpenetrated IRMOF 

0.10 

0.02 

<0.01 

IRMOF-62 (Wet) 

0.08 

<0.01 

<0.01 






MOF-199 (Dry) 

Unsaturated copper sites 

0.16 

0.24 

0.01 

MOF-199 (Wet) 

0.08 

<0.01 

0.01 






MOF-74 (Dry) 

Unsaturated zinc sites 

0.10 

0.20 

0.01 

MOF-74 (Wet) 

0.07 

<0.01 

0.01 






MOF-177 (Dry) 

Large linkers and very 
high surface area 

0.03 

0.01 

<0.01 

MOF-177 (Wet) 

0.05 

<0.01 

<0.01 






ZIF-8 (Dry) 

Sodalite structure, small 
pores 

<0.01 

<0.01 

<0.01 

ZIF-8 (Wet) 

<0.01 

<0.01 

0.23 






ASZM-T (Dry) 

Activated carbon 

0.02 

0.14 

0.02 

ASZM-T (Wet) 

0.03 

0.17 

0.11 


Of the MOFs studied, unsaturated metal sites, generally leads to the highest 
adsorption capacities, but only at low humidity conditions. There are also other possible options 
utilizing the extremely large-pore IRMOFs as these show extensive ammonia removal capacities. 
Based on results from evaluating the MOFs and ZIF studied in this effort, several 
recommendations and possible approaches for synthesizing the next set of MOFs have been 
determined: 

• Synthesize and evaluate additional MOFs with unsaturated metal sites, 
focusing on various metals for more extensive capacity and linkers that 
limit moisture adsorption. 

• Investigate impregnation techniques on high porosity MOFs, focusing on 
the metal complexes found in ASZM-T as well as other formulations for 
additional ammonia removal capacity. 

A preliminary approach has been identified consisting of two concurrent efforts. 
Figures 15 and 16 summarize the approach. 


21 













































DESIGN STRATEGY FOR UNSATURATED METAL MOFS 



22 


Figure 15. Design Strategy for Unsaturated Metal MOFs 





































































DESIGN STRATEGY FOR ZINC OXIDE/ BDC ISORETICULAR MOFS 



23 


Figure 16. Design Strategy for IRMOFs 



















































































Blank 


24 


LITERATURE CITED 


Peterson, G.W.; Mahle, J.J.; Balboa, A.; Sewell, T.L.; Karwacki, C.J.; Friday, D. Evaluation of 
Metal-Organic Frameworks for the Removal of Toxic Industrial Chemicals ; ECBC-TR-621; U.S. 
Army Edgewood Chemical Biological Center: Aberdeen Proving Ground, MD, 2008; 
UNCLASSIFIED Report (AD A483 299). 

Wong-Foy, A.G.; Matzger, A.J.; Yaghi, O.M. Exceptional IT Saturation Uptake in Microporous 
Metal-Organic Frameworks. J. Am. Chem. Soc. 2006, 128 , 3494-3495. 

Rosi, N.L.; Kim, J.; Eddaoudi, M.; Chen, B.; O’Keeffe, M.; Yaghi, O.M. Rod Packings and 
Metal-Organic Frameworks Constructed from Rod-Shaped Secondary Building Units. J. Am. 
Chem. Soc. 2005, 127 , 1504-1518. 

Rowsell. J.L.C.; Millward, A.R.; Park, K.S.; Yaghi, O.M. Hydrogen Sorption in Functionalized 
Metal-Organic Frameworks. J. Am. Chem. Soc. 2004, 126 , 5666-5667. 

Kim, J.; Chen, B.; Reineke, T.; Li, H.; Eddaoudi, M.; Moler, D.B.; O’Keeffe, M.; Yaghi, O.M. 
Assembly of Metal-Organic Frameworks from Large Organic and Inorganic Secondary Building 
Units: New Examples and Simplifying Principles for Complex Structures. J. A?n. Chem. Soc. 
2001, 123, 8239-8247. 

Rowsell, J.L.C.; Yaghi, O.M. Effects of Functionalization, Catenation, and Variation of the 
Metal Oxide and Organic Linking Units on the Low-Pressure Hydrogen Adsorption Properties of 
Metal-Organic Frameworks. J. Am. Chem. Soc. 2006, 128 , 1304-1315. 

Park, K.S.; Ni, Z.; Cote; A.P.; Choi, J.Y.; Huang, R.; Uribe-Romo, F.J.U.; Chae, H.K.; O’Keeffe, 
M.; Yaghi, O.M. Exceptional Chemical and Thermal Stability ofZcolitie lmidazolate 
Frameworks. PNAS 2006, vol. 103. no. 27, 10186-10191. 

Liang, J.; Shimizu, G.K.H. Crystalline Zinc Diphosphonate Metal-Organic Framework with 
Three-Dimensional Microporosity. Inorg. Chem. 2007,46, 10449-10451. 

Li, Y.; Yang, R. Gas Adsorption and Storage in Metal-Organic Framework MOF-177. 

Langmuir 2007,23, 12937-12944. 

Li, H; Eddaoudi, M.; O'Keeffe, M.; Yaghi, O.M. Design and Synthesis of an Exceptionally 
Stable and Highly Porous Metal-Organic Framework. Nature 1999, 402, 276-279. 

Chae, H.K.; Siberio-Percz, D.Y.; Kim, J.; Go, Y.; Eddaoudi, M.; Matzger, A.J.; O’Keeffe, M.; 
Yaghi, O.M. A Route to High Surface Area, Porosity and Inclusion of Large Molecules in 
Crystals. Nature 2004, 427, 523-527. 


25 








Park, K.S.; Ni, Z.; Cote, A.P.; Choi, J.Y.; Huang, R.; Uribe-Romo, F.J.; Chae, H.K.; O’Keeffe, 
M.; Yaghi, O.M. Exceptional Chemical and Thermal Stability of Zeolitic Imidazolate 
Frameworks. PNAS 2006, Vol. 103, No. 27, 10186-10191. 

Walton, K.S.; Snurr, R.Q. Applicability of the BET Method for Determining Surface Areas of 
Microporous Metal-Organic Frameworks. JACS 2007. 

Rouquerol, J.; Llewelly, P.; Rouquerol, F. Is the BET Equation Applicable to Microporous 
Adsorbents. Studies in Surface Science and Catalysis 2007, 160, 49-56. 

Lowell, S.; Shields, J.; Thomas, M.; Thommes, M. Characterization of Porous Solids and 
Powders: Surface Area, Pore Size and Density. Kluwer Academic Publishers: Dordrech, The 
Netherlands, 2004. 


26 


APPENDIX A 

PREVIOUS MOFS EVALUATED 


M0F4 

CBWOnCMHn) 



IRM0F4 

(awOnCuNiHO 



M0F4N 

(CuOA»V) 



A1 








Blank 


A2 


APPENDIX B 

MOF SYNTHESIS TECHNIQUES 


IRMOF-1 (MOF-5). “Triethylamine was mixed into a solution of zinc (II) 
nitrate and 1TBDC in MA’-dimethylformamide (DMF)/chlorobenzene.” (Li et al, 1999) 

IRMOF-3. “2-Aminobenzene- 1 ,4-dicarboxylic acid (0.75 g, 4.1 mmol, Aldrich) 
and zinc nitrate tetrahydrate (3.0 g, 11 mmol, EM Science) were dissolved in 100 mL of N,N- 
diethylformamide (BASF) with stirring in a 1 L wide mouth glass jar. The jar was tightly capped 
and placed in a 100 °C oven for 18 hr to yield cubic crystals. After decanting the hot mother 
liquor and rinsing with DMF, the product was immersed in chloroform (Fisher) for 3 days, 
during which the activation solvent was decanted and freshly replenished three times. The 
solvent was removed under vacuum at room temperature, yielding the porous material.” 
(Rowsell and Yaghi, 2006) 

IRMOF-62 

MOF-74. “Benzene-1,3,5-tricarboxylic acid (5.0 g, 24 mmol, Aldrich) and zinc 
nitrate tetrahydrate (10.0 g, 38 mmol, Aldrich) were dissolved in 500 mL of N,N- 
dimethylformamide (Fisher) in a 1 L wide mouth glass jar. After dissolution of the reagents, 25 
mL of deionized water was added. The jar was tightly capped and placed in an 85 °C oven for 20 
hr to yield trigonal block crystals. After decanting the hot mother liquor and rinsing with DMF, 
the product was immersed in methanol (Fisher) for 6 days, during which the activation solvent 
was decanted and freshly replenished three times. The solvent was removed under vacuum at 
270 °C, yielding the porous material.” (Rowsell and Yaghi, 2006) 

MOF-177. “A solution of DEF containing 4,4’,4”-benzene-1,3,5-triyl-tri-bcnzoic 
acid (H,BTB; 5.00 x 10' 3 g, 1.14 x 10' 5 mol) and Zn(NOQ 2 6H 2 0 (0.020 g, 6.72 x 10' 5 mol) was 
placed in a Pyrex tube of dimensions 10 mm (outer diameter), 8 mm (inner diameter), and 150 
mm (length). The sealed tube was heated at a rate of 2.0 °C min" ! to 100 °C, held at 100 °C for 
23 hr, and cooled at a rate of 0.2 °C min’ 1 to room temperature. Block-shaped crystals of 
MOF-177 were formed and isolated by washing with DEF (4x2 mL) and drying briefly in air 
(~1 min) (0.005 g, 32% based on H^BTB).” (Chae et al, 2004) 

MOF-199 (Cu-BTC, HKUST-1). “Benzene-1,3,5-tricarboxylic acid (5.0 g, 24 
mmol, Aldrich) and copper (II) nitrate hemipentahydrate (10.0 g, 43 mmol, Aldrich) were stirred 
for 1 min in 250 mL of solvent consisting of equal parts A,yV-dimethylformamide (Fisher), 
ethanol (Fisher), and deionized water in a 1 L wide mouth glass jar. The jar was tightly capped 
and placed in an 85 °C oven for 20 hr to yield small octahedral crystals. After decanting the hot 
mother liquor and rinsing with DMF, the product was immersed in dichloromethane (Fisher) for 
3 days, during which the activation solvent was decanted and freshly replenished three times. 
The solvent was removed under vacuum at 170 °C, yielding the porous material.” (Rowsell and 
Yaghi, 2006) 


B1 




ZIF-8. “A solid mixture of zinc nitrate tetrahydrate Zn(NOj)2'4H20 (0.210 g, 
8.03 x 10' 4 mol) and 2-methylimidazole (H-MelM) (0.060 g, 7.31 x 10' 4 mol) was dissolved in 
18 mL of DMF in a 20-mL vial. The vial was capped and heated at a rate of 5 °C/min to 140 °C 
in a programmable oven and held at this temperature for 24 hr, then cooled at a rate of 0.4 
°C/min to room temperature. After removal of the mother liquor from the mixture, chloroform 
(20 mL) was added to the vial. Colorless polyhedral crystals were collected from the upper 
layer, washed with DMF (10 mL x 3), and air dried for 10 min (yield: 0.032 g, 25% based on H- 
MelM).” (Park et al, 2006) 


B2