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.