A noble metal-free triphenylamine-based coordination capsule with NADH mimics as a renewable vessel for enhanced biomimetic hydrogenation

Abstract

Inspired by natural photosynthesis, artificial photocatalysis approaches that rely on nicotinamide adenine dinucleotide (NADH) and its analogues have attracted extensive attention, but face significant challenges including the over-reliance on precious-metal electron mediators for NADH regeneration and diffusion-limited charge transfer dynamics. Herein, we report the first instance of intramolecular electron transfer coupled with a pseudo-intramolecular hydride transfer mechanism through covalent grafting of the triphenylamine group and an NADH mimic into one coordination capsule, enabling enhanced cofactor regeneration and biomimetic hydrogenation in the absence of noble metals. The presence of the photosensitive triphenylamine moiety triggered a directional intramolecular electron transfer pathway induced by visible light, thereby promoting highly effective and selective NADH mimic regeneration without any assistance from a noble metal complex. Furthermore, spatial constraints within the coordination capsule ensured the regeneration selectivity of the active NADH mimic by suppressing aggregation and diffusion. Subsequently, the active NADH mimic-decorated capsule facilitates the biomimetic reduction of benzoxazinones via a pseudo-intramolecular hydride transfer, with the enhancement of hydrogenation efficiency exceeding 240% over the benchmark system based on intermolecular electron transfer. This renewable vessel-mediated photosynthesis platform exhibited enzymatic kinetics following the Michaelis–Menten mechanism, expanding new horizons for the development of a novel noble metal-free artificial catalytic system.