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[Display omitted] • Nb 2 O 5 nanorods are synthesized with a specific surface area of 166 m2/g. • The dissociative adsorption of amine on Nb 2 O 5 affords a surface complex. • The surface complex can facilitate selective oxidation of amine to imine. • TEMPO+PF 6 − acts as an electron–proton transfer mediator. • Superoxide is the dominant reactive oxygen species. Cooperative photocatalysis has gained increasing interest to better an existing redox reaction with a mediator. Herein, an ingenious system is constructed for the visible light-driven selective oxidation of a variety of amines by merging niobium oxide (Nb 2 O 5) photocatalysis with an electron–proton transfer mediator, 2,2,6,6-tetramethylpiperidine-1-oxoammonium hexafluorophosphate (TEMPO+PF 6 −). The visible light-driven dissociative adsorption of amine over Nb 2 O 5 nanorods gives rise to an amine–Nb 2 O 5 complex with a weak response to visible light (λ < 460 nm). With adding 4 mol% of TEMPO+PF 6 −, the conversion of benzylamine over Nb 2 O 5 is approximately 2.5 times that without TEMPO+PF 6 −. The proton and electron transfer between the amine–Nb 2 O 5 complex and TEMPO+PF 6 − is the key to assuring cooperative photocatalysis. Besides, the oxidant dioxygen is predominantly reduced to superoxide anion in affording the imine products. This work highlights it is feasible to ameliorate selective organic conversions over metal oxide photocatalysts with a suited mediator. [ABSTRACT FROM AUTHOR]

Cooperative photocatalysis of 2H1NA-TiO 2 with TEMPO enables the highly selective aerobic oxidation of benzylamines. [Display omitted] Solar photocatalysis is the key to resolve many environmental challenges but is usually hard to achieve over a metal oxide semiconductor. Therefore, assembling π-conjugated molecules onto semiconductors becomes an efficient approach to solar conversion via ligand-to-metal charge transfer. Here, a rational design of ligands for titanium dioxide (TiO 2) is presented to produce robust visible light photocatalysts. Three hydroxynaphthoic acids (HNAs) were selected as ligands by extending an extra benzene ring of salicylic acid (SA) at 3,4 or 4,5 or 5,6 positions. These ligands could regulate the performance of TiO 2 in which 2-hydroxy-1-naphthoic acid (2H1NA) endows the best outcome. In detail, blue light-powered cooperative photocatalysis of 2H1NA-TiO 2 with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO, 5 mol%) inaugurates the expeditious formation of imines by oxidation of amines with atmospheric oxygen (O 2). Interestingly, the increase of the O 2 pressure from 1 atm to 0.4 MPa promoted the selective oxidation of benzylamine but thereafter declined with a further boost to 0.6 MPa. Notably, an electron transfer between the oxidatively quenched 2H1NA-TiO 2 and TEMPO is established, offering a new pathway for environmental applications. This work presents a strategy in designing cutting-edge visible light photocatalysts via altering semiconductors with surface ligands. [ABSTRACT FROM AUTHOR]