Molecular simulation of carbon capture in MOFs: challenges and pitfalls

Tina Düren Institute for Materials and Processes

School of Engineering University of Edinburgh

Capture – Solid Adsorption @ UEd

http://www.eng.ed.ac.uk/carboncapture/

Hyungwoong Ahn

Process modelling for steady state and dynamic power production cycles

Daniel Friedrich Martin

Sweatman

Lev Sarkisov

Xianfeng Fan

Guilio Santori

Maria-Chiara Ferrari

Stefano Brandani

Tina Düren

Characterisation and development of

novel materials for adsorption &

membrane processes

Integration & optimisation of separation technologies (gas/liquid, membrane, adsorption, hybrid processes)

Process modelling for steady state and dynamic power production cycles

Molecular simulation of CC using MOFs, activated carbons,

mesoporous materials,

supported ionic liquids

Molecular simulation

Simulation methods based on statistical mechanics

e.g. Monte Carlo Molecular Dynamics

Output e.g. adsorption isotherms diffusion coefficients detailed picture on molecular level

Input e.g. model for fluids and solids force fields to describe interactions

adsorption isotherm

µ Tµ T

GCMC simulation

snapshot

CH4 CO2 IRMOF-1

Metal-organic frameworks

Self-assembly from different building blocks

metal organic linker

O O

OO

Br

O O

OO

NH2

Tailoring for specific applications by choosing building blocks

Different linker

molecules

Different pore shapes

Molecular simulation for screening

Screening MOFs for carbon capture with molecular simulations and quantitative structure-property relationship analysis

QSPR results in excellent prediction & ranking

A diverse range of MOFs outside the training set

MOF structure

Uptake Selectivity

Structural descriptors

GCMC ~ hours

< 5 min ~ seconds

Low Pressure CO2 Adsorption: Best MOFs have open-metal sites

• cus significantly enhance uptake of CO2 (and other molecules) at low pressures

• classical molecular simulations fail to predict the adsorption in MOFs with cus

* A. Yazaydın, et al., J. Am. Chem. Soc. 2009, 131 (51), 18198.

CO2 uptake @ 0.1 bar & RT

with cus’s

CO

2up

take

(mg/

g)

CPO-27-

Mg

CPO-27-

Ni

CPO-27-

Co

CPO-27-

ZnCuB

TCMIL

-47 ZIF-8IRM

OF-3IRM

OF-1MO

F-177

0

90

180

270 Experiment Simulation

*MOFs with cus

Challenge 1: Open metal sites

CO2 adsorption on open metal-sites

Linjiang Chen, Tina Düren School of Engineering, University of Edinburgh

Cus are challenging for classical simulations

Sum of vdW radii: 2.8 Å 2.3 Å • Interaction strong & localised

• Between physisorption & chemisorption

Combine classical molecular simulation with quantum mechanical methods to improve predictions

Combining molecular simulation with quantum mechanical methods to improve predictions of gas adsorption in MOFs with open metal sites

Information

Ab init io FFs o derived from first principles o convenient & fast computation o (potentially) transferable

QM calculations GCMC

Ab initio potential energy surface direct & minimal empirical ambiguities computationally expensive & system specific

L. Chen, et al., J. Phys. Chem. C 2012, 116(35), 18899. L. Chen, et al., J. Phys. Chem. C 2011, 115(46), 23074.

Very good predictions with ab initio derived FF: CPO-27-Mg / CO2

* P. Dietzel, et al., J. Mater. Chem. 2009, 19(39), 7362.

10-2 10-1 1000

100

200

300

400

CO2 u

ptak

e (m

g/g)

Pressure (bar)

our FF

exp.

UFF

@ 298 K *

0.2 0.4 0.6 0.8 1.0

20

30

40

Heat

of a

dsor

ptio

n (k

J/m

ol)

CO2 loading (mol/mol)

our FF

exp.

UFF

isosteric heat of adsorption

*

ab initio derived FF extendable to other metals: CPO-27-Co / CO2

Same topology with different open metal sites

Following the same route to FF development

Fewer QM calculations needed: 100 vs. 1000

our FF

exp.

UFF

10-2 10-1 1000

100

200

300

400

CO2 u

ptak

e (m

g/g)

Pressure (bar)

* @ 298 K

* A. Yazaydın, et al., J. Am. Chem. Soc. 2009, 131, 18198.

Ease of derivation: combine ab initio FF with classical FF: Cu-MOFs / CO2

ab initio FF

classical generic FFs

14

First signs that FF are transferable

CuBTC / HKUST-1 NOTT-140a

Challenge 2: Adsorption induced flexibility

CO2 adsorption in MIL-53(Sc) Linjiang Chen, Tina Düren

School of Engineering, University of Edinburgh

Carole Morrison School of Chemistry, University of Edinburgh

David Fairen-Jimenez Department of Chemical Engineering and Biotechnology, University of Cambridge

John Mowat, Paul Wright School of Chemistry, University of St Andrews

MIL-53 – Different structures depending on metal and stimulus

(c) M = Sc, Fe

(d) M = Fe, Cr

(e) M = Fe, Cr

(b) M = Sc, Fe

(a) M = Sc

Very narrow pore (vnp)

Intermediate (int)

Large pore (lp)

Fe

Fe, Sc

Sc Fe, Cr

Closed pore (cp) Narrow pore (np)

Fe, Cr, Sc

MIL-53(Sc) – breathing behaviour CO2 adsorption @ 196 K

Three phases observed (A): closed-pore form (C): large-pore form Both solved experimentally

(B1&2)

Different from known MIL-53 structures

anisotropically broadened diffraction peaks

ambiguity in indexing the cell

→ Ab inito MD

simulated

experimental

- DMF

100 K 293 K 623 K

AIMD simulations

Chen et al., J. Am. Chem. Soc., 135, 15763, 2013

empty structure

CO

2 uptake (mm

ol g-1)

Pressure (bar)

MIL-53(Sc): Response to CO2 adsorption @ 196 K

? Closed pore (cp)

Large pore (lp)

CO

2 uptake (mm

ol g-1)

Pressure (bar)

MIL-53(Sc): Response to CO2 adsorption @ 196 K + 4 CO2

+ 4 CO2

+ 2 CO2 + 2 CO2

+ 2 CO2 + 2 CO2

Narrow pore (np)

Intermediate (int)

or

?

Chen et al., J. Am. Chem. Soc., 135, 15763, 2013

MIL-53(Sc): Intermediate structure energetically favourable

np(2.2)

int(2.2)

Chen et al., J. Am. Chem. Soc., 135, 15763, 2013

int(2.2) np(2.2)

Opportunity: Integration into process modelling

Hydrogen purification using MOFs

Ana-Maria Banu, Tina Düren School of Engineering, University of Edinburgh

Daniel Friedrich, Stefano Brandani School of Engineering, University of Edinburgh

Assessing performance of MOFs

BPDC UiO-67(Zr)

+ 2 zeolites from literature

Cl2AzoBDC Zr-Cl2AzoBDC

BDC UiO-66(Zr)

BrBDC UiO-66(Zr)-Br

Assessing UiO MOFs for H2 purification from steam methane reformer offgas (SMROG)

H2

SMROG offgas

73 % H2 16 % CO2, 4 % CO, 4 % N2, 3 % CH4

Pressure swing adsorption Adsorption: 7 bar

Desorption: 1 bar

UiO-66(Zr) UiO-66(Zr)-Br UiO-67(Zr) Zr-Cl2AzoBDC zeolite

Working capacity: N(7 bar) – N(1 bar)

Impossible to tell from molecular simulation alone which material is best

SMROG: 73 % H2, 4 % N2, 3 % CH4, 4 % CO, 16 % CO2

Banu et al., Ind. Eng. Chem. Res., 52, 9946, 2013

Multiscale study to assess UiO MOFs for H2 purification

H2

SMROG offgas

CH4 CO2 CO N2 H2

3 % 16 % 4 % 4 %

73 %

Continuum model

Molecular simulation adsorption equilibrium micropore diffusion

Breakthrough curves

Ranking of materials

N2 breakthrough (1 ppm in outlet stream)

UiO-66(Zr)-Br could be promising material for H2 purification from SMROG streams

MO

F /

zeol

ite

Banu et al, Ind. Eng. Chem. Res., 52, 9946, 2013

Molecular simulation:

But be aware of the short comings Structural model of adsorbent must be known ab initio derived force fields required to describe adsorption

on open metal sites (relatively expensive) Description of flexibility requires advanced simulation

methods (expensive) Even rigid adsorbents might not be completely rigid

And know what you are doing!

A useful tool for Quantitative predictions Additional molecular-level insight Screening

Molecular simulation of �carbon capture in MOFs: challenges and pitfallsCapture – Solid Adsorption @ UEdMolecular simulationMetal-organic frameworksMolecular simulation for screeningSlide Number 6Slide Number 7Challenge 1: Open metal sitesSlide Number 9Slide Number 10Slide Number 11Slide Number 12Slide Number 13Slide Number 14Challenge 2: Adsorption induced flexibilityMIL-53 – Different structures �depending on metal and stimulusSlide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 21Opportunity: Integration into process modellingAssessing performance of MOFsAssessing UiO MOFs for H2 purification from steam methane reformer offgas (SMROG)Working capacity: N(7 bar) – N(1 bar) Multiscale study to assess UiO MOFs for H2 purificationN2 breakthrough (1 ppm in outlet stream)Slide Number 28Slide Number 29