SYNTHESIS OF DIARYL ETHERS THROUGH PHASE TRANSFER CATALYSIS WITH POTASSIUN FLUORIDE COATED ALUMINA AS A STRONG BASE

Seven diaryl ethers were synthesized with potassium fluoride coated alumina as a strong base and the addition of catalytic amount of PTC. The yield of diaryl ethers with addition of PTC was much higher than that without PTC.A discussion of the catalysis mechanism was given in this paper.

Perspectives on green synthesis and catalysis

Despite their impressive capacity to access diverse functional groups and to synthesize structurally complex molecules,the majority of the organic reactions suffers from harsh conditions,low atom economy,and hazardous waste production.The goal of our research is geared towards developing efficient methods to minimize the adverse environmental impact and contributing to chemical sustainability.Herein,we illustrate three distinct green approaches,studying the novel reactivities with environmentally innocuous reagents to improve the synthetic efficiency,utilization of natural feedstocks,and employment of green energy to facilitate various important chemical transformations.From this perspective article,we hope to provide an overview of green synthetic chemistry and inspire the expansion of the field in the future.

Mechanochemical Synthesis and Characterization of Nanocrystalline Copper-Cobalt Ferrites

Nanocrystalline copper-cobalt ferrites with composition Cu_（1-x）Co_xFe_2O_4,where x = 0.2 and 0.8,were synthesized by mechanochemical treatment of co-precipitated precursors.The ferrite powders were characterized by XRD and Mossbauer spectroscopy.Results proved obtaining of spinel ferrites with crystallite size smaller than 10 nm.Increasing of crystallite size of samples with increasing of mechanochemical treatment duration was established,too.Catalytic properties of obtained ferrites were tested in reactions of oxidation of CO,methanol and dimethyl ether.High catalytic activity of nanocrystalline copper-cobalt ferrites toward CO and CH_3OH（about 100% conversions of CO and CH_3OH at 160 ℃）and moderate activity toward（CH_3）_2O oxidation were established.The results obtained revealed that the Co/Cu atomic ratio is an important factor determinant the behavior of catalysts toward methanol and DME oxidation.

Hierarchical MoS2 intercalated clay hybrid nanosheets with enhanced catalytic activity

Emerging hierarchical MoS2/pillared-montmorillonite （MoS2/PMMT） hybrid nanosheets were successfully prepared through facile in-situ hydrothermal synthesis of MoS2 within the interlayer of cetyltrimethylammonium bromide PMMT, and their catalytic performance was evaluated by the reduction reaction of 4-nitrophenol （4-NP） using NaBH4 as a reductant. Microstructure and morphology characterization indicated that MoS2/PMMT exhibited hybrid-stacked layered structures with an interlayer spacing of 1.29 nm, and the MoS2 nanosheets were intercalated within the montmorillonite （MMT） layers, with most of the edges exposed to the outside. The catalytic activity and stability of MoS2/PMMT were both enhanced by the MMT. With the MoS2/PMMT as the catalyst, the apparent reaction rate constant of the 4-NP reduction was 0.723 min-1 and was maintained at -0.679 min-1 after five reaction cycles. The structural evolution of MoSdPMMT and the possible catalysis mechanism for the reduction reaction of 4-NP were investigated. The as-prepared MOSR/PMMT hybrid nanosheets are promising candidates for catalytic application in the water-treatment and biomedical fields. The strategy developed in this study can provide insights for designing hybrid nanosheets with diverse heterogeneous two-dimensional （2D） nanomaterials.

Single Cr atom catalytic growth of graphene

Single atoms are the ultimate minimum size limit for catalysts. Graphene, as an exciting, ultimately thin （one atom thick） material can be imaged in a transmission electron microscope with relatively few imaging artefacts. Here, we directly observe the behavior of single Cr atoms in graphene mono- and di-vacancies and, more importantly, at graphene edges. Similar studies at graphene edges with other elemental atoms, with the exception of Fe, show catalytic etching of graphene. Fe atoms have been shown to both etch and grow graphene. In contrast, Cr atoms are only observed to induce graphene growth. Complementary theoretical calculations illuminate the differences between Fe and Cr, and confirm single Cr atoms as superior catalysts for sp^2 carbon growth.