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Engineering Accessible Sites in Metal Organic Frameworks for CO2 Capture
2016 Crosscutting Research and Rare Earth Elements Portfolios Review
Pittsburgh, PA. April 22, 2016
Saki T. Golafale, Alexis McGill, Jovian Lazare, Conrad Ingram (PI) and Dinadayalane Tandabany (Co-PI)
Clark Atlanta University
Post-combustion capture Processes
Absorption into a liquid Liquid amine
Adsorption on solidsHybrid processesAdsorption/Memb
rane systems
2
Our approach: Metal organic frameworks as solid adsorbents for CO2 capture
• Highly porous crystalline solids• Very large surface area (~ 6000 m2/g)• Gas storage & separation• Tunable chemistry
Metal organic frameworks
MOF-5
3
DMF, 100 °C
Yaghi et al. Nature 402, 276-279
Other notable MOFs with high capacity CO2
• Mg-MOF74
• MOF-200
• MOF-210
There is a need to
• Isolate the metal sites to increase site accessibility• Improve stability of MOFs• Increase capacity
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Metal organic frameworks
Britt et al. PNAS vol. 106 no. 49 20637–20640
GoalSynthesize metal organic frameworks (MOFs) with adsorption sites, improve capacity and stability for CO2
Research plan
• MOFs with coordination sites within the center of the ligand [e.g., crown ether based ligands]
• MOFs with nitrogen or amine containing ligands [ e.g., pyrazine based ligands]
• MOFs with stilbene and anthracene based ligands
Research Goal and Plan
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Synthesis of diaza-crown ether ligands
A B
6
Research progress
7
Synthesis of diaza-crown ether ligands
Research progress
Transition metal diaza crown MOFs-0D
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+ Co2+
Metal within center of ligand
9
Transition metal diaza crown MOFs-1D
Metal within center of ligand
Transition metal diaza crown MOFs-2D
10Metal within center of ligand
Transition metal diaza crown MOFs-3D
11Metal within center of ligand 3 D triply interpenetrating
Modification of diaza-crown ether ligands
12Introducing ligands with side-arms
Nitrogen-containing Pyrazine organic ligand
• Is Multitopic
• Has High symmetry
• Is Rigid
• Has Ten N/O coordination sites
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MOFs with nitrogen containing ligands has shown promise for CO2
Our approach
Focus on f, d, and s blocks metals
PZTC
Open framework Large channels ~ 12Å
Kinetic diameter CO2
3.3Å
Channels contain non-coordinating water
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+ Gd/or Tb
{[Ln4(C8N2O8)3(H2O)11]10H20}n
MOF based on pyrazine and f-block metal
Activation of f-block pyrazine MOF for CO2
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Ethanol, chloroform
CO2 adsorption behavior of Ln-PZTC MOF
Micromeritics ASAP 2020
Analysis gas: CO2, N2, etc.
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CO2 adsorption isotherms of Ln-PZTC MOF
Ln-PZTC after solvent exchange with ethanol
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0.0 0.2 0.4 0.6 0.8 1.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Am
ou
nt
Ad
so
rbe
d (
mm
ol/g
)
Relative Pressure (P/Po)
Ln-PZTCB273 K
Ln-PZTCB298 K
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0.0 0.2 0.4 0.6 0.8 1.0
0.2
0.4
0.6
0.8
1.0
Am
oun
t a
dso
rbed
(m
mol/g
)
Relative pressure (P/Po)
Ln-PZTCA273 K
Ln-PZTCA298 K
Ln-PZTC after solvent exchange with chloroform
CO2 adsorption isotherms of Ln-PZTC MOF
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200 300 400 500 600 700 800
150
200
250
300
350
400
450
500
P/Q
(m
mH
g/m
mol)
Pressure (mmHg)
Equation y = a + b*x
Plot P/Q (mmHg/mmol)
Weight No Weighting
Intercept 60.63284 ± 2.18996
Slope 0.58608 ± 0.0042
Residual Sum of Squares 24.29204
Pearson's r 0.99977
R-Square(COD) 0.99954
Adj. R-Square 0.99949
200 300 400 500 600 700 800300
400
500
600
700
800
P/Q
(m
mH
g/m
mo
l)
Pressure (mmHg)
Ln-PZTCB 273 K after solvent exchange with ethanol
Ln-PZTCA273 K after solvent exchange with chloroform
Langmuir isotherm Linear fit
Sample Solventexchange
Degas temp (°C)
Analysis Temp (K)
Amount Adsorbed (mmol/g)
LnpztcA273 Chloroform 65 273 1.13
LnpztcA298 Chloroform 65 298 0.66
LnpztcB273 Ethanol 85 273 1.65
LnpztcB298 Ethanol 85 298 1.36
CO2 adsorption behavior of Ln-PZTC MOF
20Adsorption capacity improved with ethanol at 273 K and 298 K
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+ Zn2+
Pyrazine-zinc coordination polymer
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+ Mn2+
Pyrazine-manganese coordination polymer
Pyrazine-calcium coordination polymer
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+ Ca2+
Ultra-large Pore Lanthanide stilbene based MOF
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Activation of ultra-large pore Lanthanide stilbene based MOF
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Water or dichloromethane
Ln-SDC-H2O
Ln-SDC-CH2Cl2
Optical images of Ln-SDC-AS and solvent exchanged samples
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Ln-SDC-AS
Thermal stability of Ln-SDC-AS and solvent exchanged samples
27LnSDC-H2O and LnSDC-CH2Cl2 seem more stable than as synthesized
CO2 adsorption isotherms of Ln-SDC-AS at 273 and 298 K
0.0 0.2 0.4 0.6 0.8 1.0
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
Am
ou
nt
Ad
so
rbe
d (
mm
ol/g
)
Relative Pressure (P/Po)
Ln-SDC-AS-273 K
Ln-SDC-AS-298 K
28Step-wise isotherms could indicate changes in framework structure
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0.0 0.2 0.4 0.6 0.8 1.0
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
Am
ount A
dsorb
ed (
mm
ol/g)
Relative Pressure (P/Po)
Ln-SDC-H2O-273 K
Ln-SDC-H2O-298 K
CO2 adsorption isotherms of Ln-SDC-H2O at 273 and 298 K
Step-wise isotherms could indicate changes in framework structure
Lanthanide Series of anthracene based MOFs
9,10-Anthracene dicarboxylic acid (ADC)
Ln = Pr, Nd, Sm, Gd, Tb, Eu, Dy, Ho, Tm, Er, Yb
Lanthanide series of anthracene based MOFs
31Packing diagram showing the 3-D structure of Ln-ADC MOF
• Synthesized new crown-ether based ligands and new MOFs with coordination sites within the center of the ligand; structures will be further developed towards CO2 adsorption.
• Synthesized new MOFs with of nitrogen-containing ligands that showed CO2 adsorption capacity; structures will be further developed towards CO2 adsorption
• Synthesized ultra-large pore stilbene based MOF which showed CO2 adsorption potential; structures will be further developed towards CO2 adsorption
• Studied CO2 adsorption based on activation of metal sites to enhance adsorption
Conclusions
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US Department of Energy, National Energy Technology Laboratory
DOE Contract FE0022952
Chemistry Department, Clark Atlanta University
Dr. Conrad W. Ingram, advisor and PI
Acknowledgements
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Thank you.
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