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

Abstract

The process of industrial synthesis of urea produces high energy consumption and high pollution, which is bad for the environment. Photoelectrocatalytic CO₂ reduction to generate urea can avoid the aggravation of environmental pollution, but metal catalysts are commonly used for photoelectrocatalysis, and the use of metal catalysts can lead to environmental heavy metal pollution. Porphyrin-based photoelectrocatalysts with excellent photoelectronic properties were synthesized from aldolized tetrabromophenyl porphyrin (PP), and copolymers of dopamine (DA) and resveratrol (Res). The photoelectrocatalyst (COF_{_PP-DRS}) was synthesized by the Schiff base reaction. The photoelectrocatalyst exhibited good CO₂ reduction reaction (CO₂R) performance under photoelectrocatalytic conditions with a catalytic efficiency 25% higher than that of PP. The photocatalyst enabled the synthesis of urea (NH₂CONH₂) from CO₂ and NO₂⁻. NH₃, HCOOH and CO were also generated in this process. The application of COF_{_PP-DRS} can solve the problem of environmental pollution caused by the industrial synthesis of urea and the use of metal catalysts. The results, combined with infrared data, elucidated the synthesis mechanism of NH₂CONH₂.