A porphyrin-based COF to reduce CO2 and nitrite in situ for photoelectrochemical catalysis synthesis of urea

Photoelectrocatalytic catalysis of carbon dioxide (CO₂) and nitrite (NO₂^-) direct coupling to synthesise urea (NH₂CONH₂) can effectively avoid the high energy consumption and pollution of the Bosch-Meiser method. COF_{_PP-TAT} was synthesised by hydroformylation of tetrabromophenyl porphyrin (TBPP), amination of trichothecenes (TC), and linking of the two compounds through Schiff base reaction. The comprehensive characterization of COF_{_PP-TAT} showed that has rich pore structure and specific adsorption of CO₂. These characteristics are favorable for COF to synthesize urea by reducing CO₂ in a green way. COF_{_PP-TAT} exhibited a good CO₂ reduction (CO₂RR) performance under photoelectrocatalytic (PEC) conditions with the stable production of urea (NH₂CONH₂) at a rate of 0.32 µmol h^-1. That process accompanied by the production of ammonia (NH₃), formic acid (HCOOH) and carbon monoxide (CO). The synthesis mechanism was discussed.