Aluminum-based metal-organic framework support metal(II)-hydride as catalyst for the hydrogenation of carbon dioxide to formic acid: A computational study

Conversion of carbon dioxide (CO2) to value-added chemicals is achieving increased attention from an envi-ronmental and industrial perspective because it could reduce the dependency on petroleum as raw material and also its net emission into the atmosphere. We present mechanisms for the CO2 hydrogenation on the aluminum -based metal-organic framework DUT-5 support transition metal(II)-hydride in a detailed using density functional (DFT) calculations. Two different pathways, namely, Eley-Rideal (ER) and Langmuir-Hinshelwood (LH) mech-anisms are described. The ER mechanism requires activation barriers of 8.5 and 15.1 kcal/mol for the formation of formate and of formic acid steps, respectively. The first barrier is three times lower than in the LH mechanism (27.4 kcal/mol), thus favouring the ER mechanism. Supported DUT-5 MOFs are also found to have a stabilizing effect on the intermediates and transition states formed along the reaction coordinate. Finally, we screen the catalytic activities of different metals substituted into MH-DUT-5 (M = Mn, Fe, Co, Ni, and Cu) MOFs for the hydrogenation of CO2 to formic acid. It is found that NiH-DUT-5 exhibits the highest catalytic activity, based on its barriers.