Single transition metal atoms anchored on a two-dimensional polyimide covalent-organic framework as single-atom catalysts for photocatalytic CO2 reduction: A first-principles study

We systematically investigated single transition metal atoms anchored on a two-dimensional polyimide (M@2DPI) monolayer as single-atom catalysts (SACs) for photocatalytic CO2 reduction reaction (CO2RR) with first-principles calculations. The stability of M@2DPI systems is investigated first, followed by the hybrid HSE06 functional calculations on electronic structures to determine their thermodynamic feasibility for photocatalytic CO2RR. Then the optimal reaction pathways of CO2RR are identified and the highest activity is found for M@2DPI (M = Sc, Zr and La). The electronic origin of the catalytic activity is further analyzed. Finally, we found that the candidate systems except Mn-based system are able to suppress the hydrogen evolution reaction.