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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]

[Display omitted] • TBPA-COF is constructed by inserting acetylene into the olefin-linked TBP-COF. • Both TBP-COF and TBPA-COF are observed microspheres. • TBPA-COF is superior to TBP-COF for blue light photocatalysis. • Selective photocatalytic oxidation of sulfides over TBPA-COF is achieved. • Both electron and energy transfer contribute to the formation of sulfoxides. Covalent organic frameworks (COFs) with superior semiconducting properties imparted by sufficient π-conjugations and ordered structures have great potential in visible light photocatalysis. Thus, introducing extra π-conjugated rigid units into the olefin-linked COFs is effective to promote charge transfer and performance. Here, two olefin-linked COFs, TBP-COF and TBPA-COF, were synthesized by reacting 2,4,6-trimethyl-1,3,5-triazine (TMT) with 4,4′-bis(formyl)biphenyl (BFP) and bis(4-formylphenyl)acetylene (BFPA) through organic acid-induced solvothermal condensation. Both TBP-COF and TBPA-COF microspheres were with high crystallinity and uniform micropores. Owing to the insertion of acetylene, TBPA-COF possessed an extended π-conjugated structure that is conducive to smooth charge transfer. Compared to TBP-COF, TBPA-COF delivered superior photocatalytic performance on the selective aerobic oxidation of organic sulfides. Besides, both electron and energy transfer pathways contributed to the formation of sulfoxides over TBPA-COF. This work presents the ascendancy of inserting acetylene into olefin-linked COFs in building efficient visible light photocatalysts for organic oxidations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thiazolo[5,4- d ]thiazole (TzTz) is employed as the linkage to synthesize CMPs. • The TzTz-linked CMPs are thoroughly characterized. • TzTz-CMP-3 displays excellent photocatalytic activity for selective aerobic oxidation. • The photocatalytic properties of TzTz-linked CMPs could be tailored by molecular symmetry. • TzTz-CMP-3 with unprecedent activity is uncovered for the formation of sulfoxides. Developing selective formation of sulfoxides by aerobic oxidation of sulfides over highly efficient visible-light photocatalysts is an essential but challenging task. Herein, a conjugated microporous polymer (CMP) photocatalyst with the desired linkage thiazolo[5,4‑ d ]thiazole (TzTz) is presented to undertake this task. Remarkably, a catalyst-free solvothermal process afforded TzTz-CMP-3 from tetra(4-formylphenyl)-benzene and dithiooxamide. The photocatalytic activity of TzTz-CMP-3 is demonstrated with the blue light-powered selective formation of sulfoxides by aerobic oxidation of sulfides. A wide range of sulfoxides can be effectively formed by oxidation of sulfides with excellent product selectivities (up to 99 %) over the TzTz-CMP-3 photocatalyst. The more symmetric π-conjugated aromatic ring of TzTz-CMP-3 endows it with more favorable activity than the less symmetric ones. This work underscores the symmetry of building blocks for CMPs for selective photocatalytic formation of valuable organic molecules. [ABSTRACT FROM AUTHOR]

The selective aerobic oxidation of benzylamine by cooperative ARS-TNTs photocatalysis with TEMPO+BF 4 −. [Display omitted] • Anatase TNTs deliver outstanding photocatalytic activity. • ARS binds with TNTs through surface hydroxyl sites. • Electron transfer occurs smoothly between ARS-TNTs and TEMPO+BF 4 −. • With increased polarity, TEMPO+BF 4 − can increase cooperative photocatalysis. • Green light-driven selective aerobic oxidation of amines has been achieved. Visible light photocatalysis could offer an eco-friendly alternative for selective transformation of organic molecules. Herein, a cooperative system is created with alizarin red S (ARS), TiO 2 nanotubes (TNTs), and an extra redox mediator. The electron transfer between oxidatively quenched ARS-TNTs and the redox mediator is the key to secure cooperative photocatalysis. The selective aerobic oxidation of primary and secondary amines was constructed by cooperative photocatalysis of ARS-TNTs with 2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (TEMPO+BF 4 −) driven by green light. Specifically, the activity of anatase TNTs could reach about 2.2 times that of the P25 (Aeroxide P25) TiO 2 precursor. Due to increased polarity, TEMPO+BF 4 − serves more efficiently for electron transfer than (2,2,6,6-tetramethylpiperidin-1-yl)oxy (TEMPO), conferring above 1.5 times of activity that of TEMPO for the selective aerobic conversion of amines. This work features the potential of designing redox mediators in amplifying cooperative photocatalysis driven by visible light. [ABSTRACT FROM AUTHOR]