Coordination-induced in situ confinement of small-sized Ag nanoparticles on ultrathin C3N4 with strong metal–support interaction for enhanced selective CO2 photoreduction

Abstract

The construction of strong metal–support interaction (SMSI) between ultrasmall metal nanoparticles and semiconductor supports remains a pivotal challenge in developing high-performance photocatalysts for selective CO₂ conversion. Herein, we propose a coordination-induced in situ confinement strategy that synchronously achieves high dispersion of small-sized Ag nanoparticles (Ag NPs) and SMSI with ultrathin C₃N₄. Through melamine-mediated Ag–N coordination bonds, this approach orchestrates three synergistic effects: (1) coordination-induced confinement of Ag NPs (∼3.3 nm) via covalent Ag–N linkages, yielding an increase in the active site density and stability compared to conventional Ag/C₃N₄; (2) enhanced electron transfer from C₃N₄ to Ag, extending carrier lifetimes and suppressing charge recombination; (3) interfacial electronic redistribution that promotes the generation of *COOH intermediates, steering the reaction pathway toward CO with high selectivity. Furthermore, the coordination-induced thermal condensation induces nitrogen vacancies in C₃N₄, which act as molecular traps to enhance CO₂ adsorption capacity and synergize with Ag sites for efficient CO₂ activation. As a result, the optimized catalyst exhibits a remarkable CO yield of 70.63 μmol g⁻¹ h⁻¹ without the use of sacrificial agents, along with high selectivity (>98%) and excellent stability. This work establishes a universal paradigm for engineering metal–semiconductor interfaces through coordination chemistry, offering transformative insights into solar-driven CO₂-to-fuel conversion technologies.