Capture-Intensified Electrocatalytic Reduction of Postcombustion CO2 in Transporting and Catalytic Channels of Covalent Organic Frameworks

Covalent organic frameworks (COFs) have been employed for electrochemical carbon dioxide reduction (CO2RR) due to the high degree of molecular controllability. However, catalysis of the CO2RR in dilute CO(2 )conditions is hardly achieved because of the lacking ability of trapping and then transporting CO(2 )to catalytic sites in low-concentration CO2. In this work, we have achieved catalysis of the CO2RR under simulated flue gas (CO2/N-2 = 15/85, at 298 K) by constructing CO2-trapping and -transporting channels to the catalytic centers of COFs. With decorating phytic acid (PA) along the pores, the selective capture and transport ability of CO2 along the pore channels was significantly improved, and the superficial molecular H2O close to the catalytic sites was also efficient bound. The optimized catalyst (PA-Co-COF) achieved a Faradaic efficiency for CO of 86.97% at -0.7 V and a maximum turnover frequency of 1208.8 h(-1) at -1.0 V in simulated flue gas, which were 152 and 710% of those from a catalyst with bare channels. The molecular dynamics simulations and theoretical calculation revealed that PA not only promoted CO2 diffusion across the porous channels but also accelerated the formation of the intermediate COOH* and simulated the suppression of the competing hydrogen evolution reaction in the catalytic process, which contributed to higher activity and selectivity.