Theoretical investigation for adsorption of CO2 and CO on MIL-101 compounds with unsaturated metal sites

In present study, the adsorption of CO2 and CO on the metal–organic framework chromium (III) terephthalate (MIL-101) were investigated using generalized gradient approximation with DFT-D correction. Non-covalent interaction analyses (NCI) were also performed to further investigate the interaction between MIL-101 and gas molecules. The theoretical results indicated that the preferential adsorption mode of CO2 on MIL-101 is different with that of CO. The preferential adsorption mode of CO2 on MIL-101 involves one oxygen atom of CO2 (OCO2) coordinating with exposed Cr atoms through dominated Lewis acid–base interaction. The calculation results indicate that the transference from CCO to the exposed Cr atom causes the CO adsorption ability of MIL-101 to be much stronger than its corresponding CO2 adsorption ability. The theoretical investigation reveals the nature and strength of CO2 and CO adsorptions on MIL-101 and facilitates the development of new MOFs with high CO2 or CO adsorption capacity and selectivity.