No abstract

In this work, we report a new family of viologen-based ionic porous hybrid polymers (V-iPHPs) with task-specific multiple catalytic active sites toward efficient catalytic fixation of carbon dioxide (CO2) to value-added cyclic carbonates. The targeted V-iPHPs were fabricated by the solvothermal Heck reaction between two newly designed viologen ionic linkers and octavinylsilsesquioxane (VPOSS). The obtained V-iPHPs possess tunable surface areas (150–562 m2 g–1) and pore volumes (0.41–1.82 cm3 g–1) along with adjustable ionic sites (0.92–1.47 mmol g–1). Especially, a plenty of silanol (Si–OH) groups are in situ formed via breaking polyhedral oligomeric silsesquioxane cages during the synthetic process. The typical catalyst V-iPHP-1 exhibits remarkable metal-free heterogeneous catalytic activities in the CO2 fixation with diverse epoxide substrates under very mild conditions. Besides, the heterogeneous catalyst V-iPHP-1 could be easily recovered with good reusability. The excellent catalytic performance could be assigned to the synergistic catalysis of hydrogen bond donors Si–OH groups and Br– anions, abundant mesoporosities, and the hydrophobic reaction microenvironment.

No abstract

Hydroxylation of benzene is a widely studied atom economical and environmental benign reaction for producing phenol, aiming to replace the existing three-step cumene process. Aerobic oxidation of benzene with O2 is an ideal and dream process, but benzene and O2 are so inert that current systems either require expensive noble metal catalysts or wasteful sacrificial reducing agents; otherwise, phenol yields are extremely low. Here we report a dual-catalysis non-noble metal system by simultaneously using graphitic carbon nitride (C3N4) and Keggin-type polyoxometalate H5PMo10V2O40 (PMoV2) as catalysts, showing an exceptional activity for reductant-free aerobic oxidation of benzene to phenol. The dual-catalysis mechanism results in an unusual route to create phenol, in which benzene is activated on the melem unit of C3N4 and O2 by the V-O-V structure of PMoV2. This system is simple, highly efficient and thus may lead the one-step production of phenol from benzene to a more practical pathway.

A self-assembled mesoporous polyoxometalate-based ionic hybrid catalyst [TMGHA]2.4H0.6PW was prepared by combination of alcohol amino-tethered guanidinium ionic liquid [TMGHA]Cl with Keggin phosphotungstic acid H3PW12O40 (PW). Nitrogen sorption experiment validated the formation of mesostructure with moderate BET surface area, and scanning and transmission electron microscopy (SEM and TEM) showed a fluffy coral-shaped morphology for the hybrid. The contact angle test displayed that the hybrid owned hydrophilic-hydrophobic balanced surface that exhibited well wettability for both water and organic substrate like benzyl alcohol. Therefore, the hybrid can efficiently catalyze the water-mediated triphasic oxidation of benzyl alcohol with H2O2. During the reaction, the triphase catalytic system showed a special "on water" effect mainly due to the suitable mesostructure and surface wettability, thus providing some clues for the preparation of green heterogeneous catalyst.