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 β-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 β-O-4 bonds in native lignin. The capability of cleavage of β-O-4 bonds in native lignin by photogenerated thiyl radicals also demonstrates the great potential of using photogenerated thiyl radicals in organics transformations.

Room-Temperature Ionic-Liquid-Assisted Microwave Preparation of Tunable Photoluminescent Copper-Indium-Zinc-Sulfide Quantum Dots

A facile approach towards photoluminescent (PL) Cu-In-Zn-S quantum dots (CIZS QDs) has been developed, comprising microwave treatment with the assist of room-temperature ionic liquid (RTIL). Because of its high polarizability, RTIL served as a microwave absorbent, which resulted in the increase of the instantaneous nucleation rate and the rapid synthesis of CIZS QDs at low temperature. Moreover, the surface decoration of QDs with RTIL can passivate the surface defects greatly. The PL intensity of the CIZS QDs depends on the anion species, alkyl chain length of the RTIL, and the metal element ratios of the QDs. On the basis of the variable PL peak position and extended luminescence lifetime of the CIZS QDs, the superior emission behavior of the QDs was confirmed by surface etching with fluoride produced by the hydrolysis of RTIL 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF₄ ). Moreover, the intermediate alkyl chain length of the RTIL can avoid aggregation, which results in the construction of CIZS QDs with homogenous size distribution. The shape-controlled CIZS QDs show a broadened tunable emission peak from 677 to 579 nm compared with that of QDs prepared by a conventional one-pot method by mixing the raw materials. CIZS QDs also exhibit a high quantum yield (QY) of 24.1 % after coating with a ZnS shell. This method is expected to be a useful technique for the rapid synthesis of multiple QDs with a wider range of emission wavelengths and higher QY for a variety of applications.