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 garnered extensive attention, but face marked challenges including the overreliance on precious-metal electron mediators for NADH regeneration and the 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 triphenylamine group and 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 of noble metal complex. Futhermore, spatial constraint within the coordination capsule ensured the regeneration selectivity of the active NADH mimic by suppressing the aggregation and diffusion. Subsequently, the active NADH mimics-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 novel noble metal-free artificial catalytic system.