Understanding Trends in CO2 Adsorption in Metal-Organic Frameworks with Open-Metal Sites.
Using van der Waals-corrected density functional theory and a local chemical bond analysis, we study and explain trends in the binding between CO2 and open-metal coordination sites within a series of two metal-organic frameworks (MOFs), BTT, and MOF-74 for Ca, Mg, and nine divalent transition-metal cations. We find that Ti and V result in the largest CO2 binding energies and show that for these cations the CO2 binding energies for both structure types are twice the value expected based on pure electrostatics. We associate this behavior with the specific electronic configuration of the divalent cations and symmetry of the metal coordination site upon CO2 binding, which result in empty antibonding orbitals between CO2 and the metal cation. We demonstrate that a chemical bond analysis and electrostatic considerations can be used to predict trends of CO2 binding affinities to MOFs with transition-metal cations.
†Laboratoire Science et Ingénierie des Matériaux et Procédés (SIMaP), Grenoble-INP, UMR CNRS-5266, 1130 rue de la Piscine, 38402 Saint Martin d'Hères, France.|‡Department of Chemical and Biomolecular Engineering, University of California, 201 Gilman Hall, Berkeley, California 94720, United States.|§Molecular Foundry, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, California 94720, United States.
Roberta
R
Poloni
‡Department of Chemical and Biomolecular Engineering, University of California, 201 Gilman Hall, Berkeley, California 94720, United States.|§Molecular Foundry, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, California 94720, United States.
Kyuho
K
Lee
§Molecular Foundry, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, California 94720, United States.
Robert F
RF
Berger
‡Department of Chemical and Biomolecular Engineering, University of California, 201 Gilman Hall, Berkeley, California 94720, United States.
Berend
B
Smit
§Molecular Foundry, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, California 94720, United States.|∥Department of Physics, University of California, Berkeley, 366 LeConte Hall MC 7300, Berkeley, California 94720, United States.|⊥Kavli Energy NanoSciences Institute at Berkeley, Berkeley, California 94720, United States.
Jeffrey B
JB
Neaton
CO2 capture; crystal field theory; density functional theory; metal−organic frameworks