An ionic copolymer catalyst with nanopores, large surface area, high ionic density, and superior basicity was prepared via the radical copolymerization of amino-functionalized ionic liquid bromide and divinylbenzene, followed with a hydroxyl exchange for removing bromonium. Evaluated in chemical fixation of CO2 with epoxides into cyclic carbonates in the absence of any solvent and basic additive, the nanoporous copolymer catalyst showed high and stable activity, superior to various control catalysts including the halogen-containing analogue. Further, high yields were obtained over a wide scope of substrates including aliphatic long carbon-chain alkyl epoxides and internal epoxide, even under atmospheric pressure and less than 100 °C for the majority of the substrates. On the basis of in situ Fourier transform infrared (FT-IR) investigation and density functional theory (DFT) calculation for the reaction intermediates, we proposed a possible reaction mechanism accounting for the superior catalytic activity of the ionic copolymer. The specifically prepared ionic copolymer material of this work features highly stable, noncorrosive, and sustainable catalysis and, thus, may be a new possibility for efficient chemical fixation of CO2 since it is an environmentally friendly, metal-free solid catalyst.

No abstract

A novel carbon-based hybrid is composed of Ndoped ordered mesoporous carbon (NC) and polyoxometalate (POM) based ionic salt (IL-POM), constructing the first efficient non-noble metal heterogeneous catalyst for reductantfree hydroxylation of benzene to phenol with molecular oxygen. Enhanced activity and reusability were achieved and were even better than the previous noble metal involved system. The newly task-specifically designed dicationic ionic liquid tethered with the nitrile group contributed to the high efficiency and heterogeneous property. Systematic structure− activity analysis revealed that the superior activity for this difficult reaction came from the simultaneous activation of benzene by NC and O 2 by V species of IL-POM. This work suggests a new green reaction pathway toward heterogeneous aerobic hydroxylation of the C sp2 -H bond in π-conjugated aromatic molecules.

No abstract

Carbon materials are promising environmentally-benign heterogeneous catalysts but design of effective carbon catalysts with comparable or even superior performance to metal-based ones is highly challengeable. Herein, N-doped mesoporous carbons with the surface enriched with abundant oxygen species were synthesized by a facile hydrothermal doping strategy in the self-assembly of phenolic resin, followed with a carbonization process. Direct hydroxylation of benzene to phenol with O 2 as the sole oxidant was effectively catalyzed by these carbons, affording a yield superior or comparable to previous efficient transition metal and even noble metal-based catalysts. The catalyst is facilely recovered and stably reused. The surface carbonyl groups are the active sites for O 2 activation (rate determining step) to generate hydroxyl radicals, which are the reactive oxygen species to oxidize the benzene. This methodology is readily extendable to the oxidation of various other benzene derivatives.[a] W.

No abstract

A highly efficient Pd‐containing catalytic system for the intermolecular direct C−H homocoupling of benzene to biphenyl has been developed. The catalytic system was composed of Pd(OAc)2 with trifluoromethanesulfonic acid (TfOH) as an additive and O2 as the sole oxygen source in the absence of any metal‐containing cocatalyst. An excellent efficiency of PdII with the acidic additive was attained in the aerobic oxidation of benzene to biphenyl. A high yield (25.3 %) and selectivity (98 %) were achieved by using a small amount of Pd(OAc)2 (0.07 mol %) and TfOH, which gave a high turnover number (180) for Pd species. Theoretical calculation by DFT and UV/Vis absorption spectra illustrated that the formation of electropositive PdII species in the presence of TfOH contributed to the high efficiency of the catalytic system.

No abstract