Spatial Confinement of Solution‐Inaccessible Single‐Site Cu(I) in a Molecular Titanium–Oxo Cage for Efficient Photo‐Electrocatalytic Urea Synthesis

Abstract

Abstract We introduce a precisely engineered molecular titanium‐oxo cage, Ti 16 O 24 Bz 24 (denoted as Ti 16 ; Bz = C 6 H 5 CO 2 ), designed to host a spatially confined Cu + single‐atom site, that enables efficient and selective C─N coupling from CO 2 and NO 3 − under photo‐electrocatalytic (PEC) conditions, providing a molecular‐level blueprint for multi‐reactant coupling catalysis. Ti 16 features a large internal cavity assembled from TiO 6 octahedra shielded by a hydrophobic benzoate shell. Metalation of Ti 16 with CuCl 2 /NaBH 4 incorporates Cu + ions, displacing encapsulated H 3 O + and enabling the synthesis of Ti 16 Cu x ( x = 0.25–8). Among the Ti 16 Cu x series, Ti 16 Cu 2 demonstrates optimal performance under PEC conditions, achieving a high urea yield of 20 mmol g cat −1 h −1 with a Faradaic efficiency of 85% and a selectivity of 62% at −0.6 V versus RHE, outperforming most reported Cu‐based systems. Spectroscopic and structural analyses reveal that C─N bond formation occurs via coupling of *CO and *NO species at the confined Cu sites, highlighting the essential role of the molecular cage in stabilizing reactive species and facilitating their interaction. This work establishes cage‐like metal–oxo clusters as an atomically precise and versatile molecular platform for developing highly selective single‐atom catalysts for challenging multi‐reactant coupling reactions.