A DFT study on Pt single atom loaded COF for efficient photocatalytic CO2 reduction

Photocatalytic CO2 reduction provides a promising strategy for the alleviation of greenhouse effect and energy shortage problem. Metal single atom modification is an effective method to improve the CO2 reduction performance of covalent organic framework (COF) photocatalysts, while the intrinsic mechanism is not revealed in depth. Herein, a Pt-COF photocatalytic system was constructed by embedding Pt single atom in TFPT-TMT-COF (TFPT: 1,3,5-tris(4-formylphenyl)-triazine, TMT: 2,4,6-trimethyl-1,3,5-triazine). Based on density functional theory (DFT) calculation, the geometric structure and electronic property of Pt-COF were investigated, and the CO2 adsorption and reduction reaction process on Pt-COF were simulated. The results show that the Pt atom can be steadily anchored in COF via the formation of Pt–N and Pt–C bonds. Moreover, there is strong electronic interaction between Pt and COF. The incorporation of Pt atom benefits the CO2 reduction activity of COF from multiple aspects: (ⅰ) reducing the band gap and improving light absorption; (ⅱ) enhancing CO2 adsorption and activating the CO2 molecule; (ⅲ) decreasing the energy barrier in the hydrogenation step of CO2→COOH, thus facilitating CO2 conversion to CO; (ⅳ) inhibiting the hydrogenation of CO, thereby increasing the selectivity of CO. This work brings a novel insight into the excellent CO2 reduction performance of Pt modified COF, and provides useful references for the design of single atom photocatalysts.