Two-Dimensional Fe-Hexaaminobenzene Metal–Organic Frameworks as Promising CO2 Catalysts with High Activity and Selectivity

Motivated by the recent synthesis of two-dimensional (2D) metal–organic frameworks TM 3 (HAB) 2 (TM = Fe, Co, Ni, Cu; HAB = hexaaminobenzene) with good intrinsic conductivity, for the first time, we explore the CO 2 conversion performance of these 2D sheets using density functional theory combined with the computational hydrogen electrode model. We find Fe 3 (HAB) 2 as a promising material for electrocatalytic CO 2 reduction reaction. Reaction energy calculations identify the preferred pathway for CO 2 conversion to CH 3 OH on Fe 3 (HAB) 2 via an “RWGS + CO-hydro” process in which the corresponding free energy change is 0.69 eV and the activation energy barrier is 1.36 eV. In addition, the formation of *CHO through the hydrogenation of *CO is the rate-limiting step with the highest thermodynamic and kinetic barrier in elementary reactions. Compared with Cu(211), which exhibits the highest catalytic activity among all transition metals, Fe 3 (HAB) 2 has a better catalytic activity with a lower overpotential for CO 2 reduction and a better selectivity with a much higher overpotential for the side reaction.