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

4

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

8

+ 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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