Design of Boron and Transition Metal Embedded Two-Dimensional Porous Carbon Nitride for Electrocatalytic Synthesis of Urea

Electrocatalytic coupling of CO and N2 to synthesize urea under ambient conditions is considered a promising strategy to replace traditional industrial technology. It is crucial to find efficient electrocatalysts that can adsorb and activate N2 and promote the C–N coupling reaction. Herein, a new two-dimensional porous carbon nitride material with multiactive sites is designed, in which boron and transition metal are embedded. Through a series of screening, B2Cr2, B2Mn2, and B2Os2 are predicted to be potential electrocatalysts for urea synthesis. Mechanistic studies are performed on bidentate metal–metal and metal–boron sites, and both NCON and CO mechanisms are explored. The electronic structure analysis shows that there is a strong N2 chemical adsorption within the bidentate site and that the N≡N bond is significantly activated. A new mechanism where free CO is inserted for C–N coupling within the two-dimensional porous structure is proposed.