Depolymerization of Native Lignin over Thiol Capped Ultrathin ZnIn2S4 Microbelts Mediated by Photogenerated Thiyl Radical.

The valorization of native lignin to functionalized aromatic compounds under visible light is appealing yet challenging. In this communication, colloidal mercaptoalkanoic acid capped ultrathin ZnIn2S4 (ZIS) microbelts was successfully fabricated, which was used as a superior catalyst for depolymerization of native lignin in birch woodmeal under visible light, with an optimum yield of 28.8 wt % to functionalized aromatic monomers achieved in 8 h. The capped mercaptoalkanoic acid not only enables a solvent modulated reversible interchange of ZIS between the colloidal state for efficient reaction and the aggregated state for facile separation, but also serves as a precursor for light initiated generation of reactive thiyl radical for highly selective cleavage of ß-O-4 bond in native lignin. This work provides a green and efficient strategy for the depolymerization of native lignin to functionalized aromatic monomers under mild conditions, which involves a new mechanism for the cleavage of ß-O-4 bonds in native lignin. The capability of cleavage of ß-O-4 bonds in native lignin by photogenerated thiyl radicals also demonstrates the great potential of using photogenerated thiyl radicals in organics transformations.

Facile fabrication of ternary NiTiFe-LDH ultrathin nanosheets for efficient conversion of amines into imines under visible light.

Ternary NiTiFe-LDH with an ultrathin nanosheet morphology was successfully fabricated via a facile co-precipitation method, followed by refluxing, and was used as a catalyst for oxidative coupling of amines to produce imines under visible light. The obvious superior activity observed in NiTiFe-LDH ultrathin nanosheets compared with binary NiTi-LDH and bulk NiTiFe-LDH can be ascribed to an enhanced light absorption capability caused by the introduction of Fe3+ ions as well as the ultrathin nanosheets which can minimize the recombination of the photogenerated charge carriers and provide more catalytically active sites for the reaction. As a result, more catalytically active O2˙- radicals are generated over NiTiFe-LDH ultrathin nanosheets, which leads to their superior activity. This study not only shows the possibility of using LDHs in photocatalytic organic transformations but also demonstrates an effective strategy to promote the activity of LDH-based photocatalysts via simultaneous composition and morphology modulation of LDHs.

Efficient visible light-initiated hydrogenation of nitrobenzene for chemoselective production of aniline, azoxybenzene, azobenzene and hydrazobenzene over CQDs/CdS nanocomposites.

Carbon quantum dot (CQD)-decorated CdS nanocomposites were successfully fabricated via the self-assembly of CdS in the presence of preformed CQDs and were found to be efficient photocatalysts for the hydrogenation of nitrobenzene under visible light. Due to the presence of the frustrated Lewis acid-base pairs (FLPs) in their structure, CQDs act as an efficient catalyst to promote the proton-coupled hydrogenation of nitrobenzene over CQDs/CdS nanocomposites. Controllable and chemoselective hydrogenation of nitrobenzene to produce aniline, azoxybenzene, azobenzene and hydrazobenzene can be realized over CQDs/CdS via simply regulating the reaction medium including the hydrogen source, the solvent and the alkalinity. This study provides a highly efficient and economical photocatalytic system for the controllable and chemoselective hydrogenation of nitrobenzene under visible light. This work also highlights the great potential of semiconductor-based photocatalysis in light-initiated organic syntheses.