Phosphorus Quantum Dots-Facilitated Enrichment of Electrons on g-C3N4 Hollow Tubes for Visible-Light-Driven Nicotinamide Adenine Dinucleotide Regeneration

Nicotinamide cofactors (e.g., NADH) are essential hydrogen sources for the majority of enzyme reduction reactions. Currently, highly efficient and in situ cofactor regeneration is urgently required but remains challenging. In this study, red phosphorus quantum dots were decorated onto graphitic carbon nitride hollow tubes to prepare high-performance heterojunction photocatalyst (g-C3N4-HTs@rP-QDs) for visible-light-driven NADH regeneration. Energy band analysis combined with photoelectrochemical measurements demonstrates rP-QDs not only act as additional photosensitizers for charge generation but also constitute a type II heterojunction with g-C3N4-HTs for charge transfer, facilitating enrichment of electrons on the g-C3N4-HTs surface. Such enrichment of electrons for g-C3N4-HTs@rP-QDs offers ∼5 times higher reducing active sites than bulk g-C3N4 to trigger the NADH regeneration reaction under visible-light (LED, 405 nm) illumination, thus acquiring superior NADH regeneration efficiency with an initial reaction rate (2 min) of 0.247 ± 0.012 mmol g–1 min–1. In the concerned experimental range, higher g-C3N4-HTs/rP-QDs mass ratios or light intensities that are beneficial for the electron enrichment could result in enhanced regeneration efficiency. The bioactivity of NADH toward enzyme catalysis is further demonstrated by alcohol dehydrogenase-catalyzed hydrogenation of formaldehyde, which enables the sustainable production of methanol.