Rational Design of Cu–O–Mo Dual Sites with Fast Electron Transfer for Enhanced Photocatalytic Amines with Alcohols to Imine

Solar-light-driven imine synthesis from aniline and benzyl alcohol requires selective C–OH bond activation and C═N stabilization. Enhancing efficiency relies on precise spatial control of catalytic sites, making the achievement of high activity and selectivity a persistent challenge. Here, we synthesized a dual-metal-site catalyst, [Cu2(4,4′-bipy)(Mo2O8)·2.75H2O]n (CuMo-MOF), featuring Cu and Mo centers bridged by μ-oxo groups with an average Cu···Mo distance of 3.3527 Å. The structurally defined framework provides distinct Cu/Mo coordination environments and facilitates substrate access and electron transfer, thereby enabling cooperative catalytic reactivity. Notably, the CuMo-MOF exhibits excellent photocatalytic activity (100% selectivity for imine and >99.9% conversion of aniline) for the coupling of amines with alcohols under 10 W LED illumination (λ = 420–425 nm) and retains high activity over five cycles. In situ IR spectroscopy reveales an enhanced C═O stretching band on CuMo-MOF, indicating that the Cu–O–Mo fragment facilitates benzyl alcohol oxidation. Control experiments and DFT calculations reveal the detailed oxidation pathway and the synergistic effect of dual active sites. Mo sites govern benzyl alcohol adsorption and formation of ·O2–, and Cu sites mediate benzyl alcohol oxygenation as the rate-determining step. This work provides an alternative solar-driven catalytic platform for the sustainable production of value-added chemicals.