Dual‐Site Engineering of a Noble‐Metal‐Free Z‐Scheme Heterojunction for Radical‐Kinetics‐Steered Selective C–C Coupling

ABSTRACT

Selective photocatalytic C─C homocoupling of amines remains challenging due to uncontrollable radical kinetics and over‐oxidation. Herein, we construct a noble‐metal‐free Z‐scheme Cr‐TiO ₂ @N‐C/CdS heterojunction photocatalyst that decouples thermodynamic and kinetic control through a dual‐site strategy. The incorporation of N‐doped carbon buffer layer not only resolves the intrinsic work function mismatch between Cr‐TiO ₂ and CdS for efficient Z‐scheme charge transfer, but also facilitates rational control over the sequential arrangement of interfaces, thereby precisely regulating the coupling sites. Thermodynamically, Cr‐induced impurity levels near the valence band edge of TiO ₂ moderate hole oxidation potential, preventing over‐oxidation of benzylamine. Kinetically, at the CdS surface, strong electronic interactions between surface three‐coordinated Cd atoms and the Ph( ^• CH)NH ₂ radical impede further oxidation to imine, maintaining a high local radical concentration and exclusively driving C─C coupling. Consequently, under blue light, this heterojunction selectively converts benzylamine to the corresponding diamine (∼80% selectivity and an apparent quantum yield of 2.78%) with simultaneous high‐rate hydrogen evolution through a concerted proton‐coupled electron transfer pathway. This selectivity is broadly applicable to other benzylamine derivatives and benzyl alcohol systems. This work demonstrates that coordinated regulation of redox and surface reaction sites provides a robust strategy for achieving controllable radical dynamics and selective C─C bond synthesis.