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Pickering emulsions are an excellent platform for interfacial catalysis. However, developing simple and efficient strategies to achieve product separation and catalyst and emulsifier recovery is still a challenge. Herein, we report the reversible transition between emulsification and demulsification of a light‐responsive Pickering emulsion, triggered by alternating between UV and visible light irradiation. The Pickering emulsion is fabricated from Pd‐supported silica nanoparticles, azobenzene ionic liquid surfactant, n‐octane, and water. This phase behavior is attributed to the adsorption of azobenzene ionic liquid surfactant on the surface of the nanoparticles and the light‐responsive activity of ionic liquid surfactant. The Pickering emulsion can be used as a microreactor that enables catalytic reaction, product separation as well as emulsifier and catalyst recycling. Catalytic hydrogenation of unsaturated hydrocarbons at room temperature and atmospheric pressure has been performed in this system to demonstrate product separation and emulsifier and catalyst re‐use. [ABSTRACT FROM AUTHOR]

Although significant progress has been made in the synthesis of covalent organic frameworks (COFs) in recent years, the construction of hierarchical pores in such materials remains a great challenge. Herein, we report a facile synthesis of hierarchically porous COFs (HP-COFs) under mild conditions in ionic liquids 1-alkyl-3-methylimidazolium tetrafluoroborates ([Cnmim][BF4], n = 4, 6, 10). It has been found that apart from the inherent micropores, a large mesoporous structure has been produced in the COFs in which the size of pores can be simply tuned by adjusting the alkyl chain length of the ionic liquids. These mesopores have been confirmed by N2 sorption and electron microscopy techniques. Importantly, this approach is applicable for the preparation of various HP-COFs, such as imine and hydrazone based COFs, which are quite difficult to acquire through traditional methods. In addition, these HP-COFs show highly effective catalytic performance for C–C bond formation, especially for large size molecule based C–C coupling reactions in comparison with uni-pore COFs. [ABSTRACT FROM AUTHOR]

The conversion of CO2 into valuable chemicals is an ideal pathway for CO2 utilization in industry, although the development of highly efficient catalysts remains a challenge. Herein, the design and synthesis of two covalent organic frameworks (COFs) functionalized with imidazolium salts were reported as catalysts for CO2 conversion. The resultant COFs possessed highly crystalline structures, showed high stability and surface area, and contained dense catalytic active sites on the pore walls. They exhibited outstanding catalytic performances for the reaction of CO2 with epoxides without any solvent or cocatalyst under mild conditions and afforded a record turnover number of 495 000. In addition, the COFs could serve as effective catalysts in the reductive reaction of CO2 with amines. The results presented here thus demonstrate the exceptional potential of the functionalized COFs for various challenging CO2 transformations. [ABSTRACT FROM AUTHOR]

Nitrogen dioxide is demonstrated to be an effective catalyst precursor for the iodination of alkoxy-substituted benzenes and naphthalenes. Different from the transition metal catalysts, nitrogen dioxide can be easily separated from the final products, and is free of heavy metal waste. Although the present catalyst precursor is toxic, it does not stain the final products due to its low-boiling character. No other reagents apart from 0.5 equiv. of iodine (I2), 6.5 mol% nitrogen dioxide and acetonitrile solvent were used in the iodination, and basically all the iodine atoms in the iodine source were transferred to the iodination products, showing that the presented protocol is highly atom-economic and practical. [ABSTRACT FROM AUTHOR]

Recently, the efficient chemical fixation of carbon dioxide (CO2) into high value chemicals without using noble metal catalysts has become extremely appealing from the viewpoint of sustainable chemistry. In this work, a one-pot three component reaction of propargylic alcohols, anines and CO2 that can proceed in an atom economy and environmentally benign manner by combination of CuI and tetrabutylphosphonium imidazol ([P4444][Im]) as a catalyst was described. Catalysis studies indicate that this catalytic system is an effective catalyst for the conversion of CO2 into oxazolidinones at room temperature and ambient pressure without any solvent. The results provide a useful way to design novel noble metal-free catalyst systems for the transformation of CO2 into other valuable compounds. [ABSTRACT FROM AUTHOR]

The concerted catalysis throughout multiple elementary steps is key to impel sluggish hydrogen evolution reaction (HER). Herein, NiMo/Mo 2 N/NC(500-R) array is constructed by embedding densely packed NiMo/Mo 2 N heterojunctions into nanorod skeleton of nitrogen-rich derived carbons (NC), then followed by electrochemical surface reconstruction. The great electrochemical surface area of resultant electrocatalyst implies fully-exposed concerted diatomic-ensembles. The ensemble effect of unique heteronanojunction induces charge polarizations between Mo and Ni species, gives pseudocapacitance comparable to supercapacitors, and pumps mass transfers to refresh entire HER process. The exceptional activity is demonstrated by ultra-low overpotentials of 5.8 and 200.6 mV respectively at 10 and 1000 mA cm−2, the impressive durability is indicated by lasting alkaline HER for 1000 h at 1 A cm−2. Moreover, the performances in water-alkali electrolyzer outperform most reported catalysts. This work presents valuable insights into concerted catalysis and designing efficient and durable electrocatalysts by ensemble effect from different metal heterojunctions for commercial applications. [Display omitted] • Well-separated heteronanojunctions impart the enhanced intrinsic activity to array. • Ensemble effect refreshes the concerted diatomic sites by charge polarizations. • Electrocatalyst delivers ultra-low overpotentials in alkaline hydrogen evolution. • Striking durability makes electrocatalyst commercializable in hydrogen production. • In-depth insights offer guidance to design efficient and durable electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zirconia crystals influence catalytic behavior of Pb-based catalysts. • TZ-Pb shows higher dispersion degree, larger surface area and more Lewis acid sites. • TZ-Pb is highly active and recyclable for MPC disproportionation. • Tetragonal zirconia is more suitable and stable crystalline phase compared to the monoclinic one. • This work provides prospective reference for extensive utility of zirconia polymorphs in various catalytic applications. Zirconia supported Pb-based catalysts with purely tetragonal/monoclinic crystals were prepared and analyzed well by XRD, TEM-EDS, XPS, H 2 -TPR, BET, Py-IR and NH 3 -TPD techniques. The results indicate that zirconia polymorph has great effect on their structure and catalytic property for the synthesis of diphenyl carbonate (DPC) through methyl phenyl carbonate (MPC) disproportionation due to the differences of surface chemical properties, and tetragonal zirconia supported lead catalyst (TZ-Pb) shows bigger dispersion degree of PbO, higher surface area and Lewis acid amounts and thereby exhibits higher catalytic activity and selectivity compared to monoclinic zirconia supported catalyst (MZ-Pb). Furthermore, TZ-Pb shows better reusability due to strong metal-support interaction and may be readily recycled for at least four times without remarkable reactivity loss. This work provides a prospective reference for the facile and efficient synthesis of zirconia polymorph materials in various catalysis applications. [ABSTRACT FROM AUTHOR]

HNO 3 was demonstrated to be an effective catalyst for aerobic oxidation of benzylic sp 3 C H bonds under additive-free conditions. A series of isochromans, xanthenes and fluorenes underwent this transformation to give the targeted products in low to high yields under the catalysis of HNO 3 , which provided an effective method for the synthesis of the synthetically and biologically valued isochromanones, xanthones and 9-fluorenones. [ABSTRACT FROM AUTHOR]

A method for the bromination of alkoxy-substituted benzenes and naphthalenes was developed by using the residual oxygen in the reaction tube as the oxidant, and [Bmim]NO 3 (1-butyl-3-methylimidazolium nitrate) ionic liquid as both the catalyst and the solvent. No other reagent apart from the ionic liquid and molecular bromine was used in the reactions, and basically all the bromine atoms in the bromine source were transferred to the bromination products, showing that the presented protocol is highly atom economic and practical. [ABSTRACT FROM AUTHOR]

Nitrogen dioxide is demonstrated to be an effective catalyst precursor for the iodination of alkoxy-substituted benzenes and naphthalenes. [ABSTRACT FROM AUTHOR]

An effective reductive cleavage of inert aryl C-O bonds that employs iron(III) acetylacetonate as the catalyst precursor and LiAlH4 as the reducing agent is developed. [ABSTRACT FROM AUTHOR]

Abstract: A cobalt catalyst has been demonstrated, for the first time, to be effective for the reductive cleavage of inert aromatic C O bonds with high selectivity. Compared with previous Ni catalysts, the cobalt catalyst reported here is more commercially available and air-stable. [Copyright &y& Elsevier]

Abstract: A novel method was proposed for successful fabrication of CuS nanostructures with various morphologies. At the ionic liquids (ILs)-modulated CHCl3–H2O interface, copper cupferronate [Cu(cup)2] in CHCl3 reacted with thiourea in water to generate CuS nanostructures via a solvothermal reaction process. The effects of alkyl chain length of imidazolium cations and nature of anions of the ILs, molar ratio of Cu(cup)2 to thiourea, the reaction temperature and time on the morphology of the products were studied systematically. It was shown that by changing alkyl chain length of imidazolium cations and nature of anions of the ILs, CuS nanostructures with various morphologies, including flowers, urchins, large nanodisks and nanoparticles, could be obtained at the liquid–liquid interface, and the ILs played important template roles in directing the formation of CuS nanostructures. Furthermore, the as-prepared CuS samples exhibited high catalytic activity for photodegradation of methyl orange and thermal decomposition of ammonium perchlorate. [Copyright &y& Elsevier]

Catalyst is recyclable and reusable at least 6 times. [ABSTRACT FROM AUTHOR]

The reaction of pentadienones (I) with pyridines (II) at room temperature leads to a variety of 3,4-dihydroquinolizin-2-ones (III), whilst the prolonged reaction at higher temperature is accompanied by an oxidation of dihydroquinolizinones with air to afford corresponding quinolizinones as sole products. [ABSTRACT FROM AUTHOR]