Precisely Bonded Fe─Cu Diatomic Sites with Nitrogen‐Bridged Coordination on Hollow C₃N₄ Spheres for Efficient C─N Coupling and Selective Photocatalytic Urea Synthesis

Abstract

AbstractThe photocatalytic synthesis of urea from CO2 and N2 co‐reduction presents a promising alternative to the conventional energy‐intensive Haber–Bosch process. However, competitive adsorption on the catalyst surface often limits selectivity and yield. Here, we designed hollow graphitic carbon nitride (g‐C3N4) spheres, which serve as a high surface area scaffold for precise anchoring of Fe─Cu diatomic sites. Hollow architecture enhances light harvesting via inner‐scattering effects and charge separation. Each Fe─Cu site is coordinated with two nitrogen atoms, forming N2─Fe1─Cu1─N2 /C3N4 DAC (hereafter referred to as FeCu/CN), which enables cooperative activation of CO2 and N2, in contrast to monodispersed diatomic (Fe+Cu/CN), and single‐atom catalysts (Fe/CN, Cu/CN). The FeCu/CN bonded pairs serve as highly efficient active centers, facilitating the synergistic adsorption and activation of multiple reactants. Specifically, during the co‐reduction of CO2 and N2, the Fe1 site preferentially adsorbs and activates CO2, while bonded Cu1 sites stabilize N2 on FeCu/CN and enable synergistic C─N coupling through the formation of *NCON intermediates. As a result, the FeCu/CN achieves an exceptional urea yield of 7.40 mg·gcat−1·h−1 with a 38.58% selectivity under visible light irradiation. Our findings highlight the crucial role of atomic‐level coordination in multireactants and offer insights into the C─N coupling for value‐added products using CO2 and N2 as feedstock.