Electronic Tuning of Active Sites in Bifunctional Covalent Organic Frameworks for Photoassisted CO2 Electrocatalytic Full Reaction

Realizing simultaneously energy-efficiency improvement and green economic implementation remains a daunting challenge in addressing the low-efficiency issues of CO2 electroreduction to meet the sustainable development strategy. Here, we propose a series of porphyrin-based COFs (TTCOF-M, M = Co, Ni, and Cu) as model catalysts to study the hybrid CO2 electrocatalytic full reaction for the first time, during which the catalysts can simultaneously accomplish photoassisted CO2 electroreduction and 4-nitrophenol (4-NP) mineralization. As model catalysts, the effects of various parameters have been intensively studied from typical tandem electro-reactions to extended photoassisted ones. Specifically, TTCOF-Co can achieve the cathodic reduction efficiency increasing from 90 to 96% (−0.7 V) after illumination and simultaneously 5 times shortened reaction time with a 4-NP degradation efficiency of ∼99%. Notably, the 4-NP mineralization rate is calculated to be ∼93.51% with ∼30.27 mmol/g/h CO2 production rate, and a rarely investigated mechanism relating to the 4-NP electro-degradation has been intensively studied.