A novel catalysis-assisted gelation strategy is exploited to assemble a catalogue of covalent gels with superior stability from small molecules via strong covalent bonding. Triazole-based covalent gels with hierarchical porous structure and large surface area are fabricated based on copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) polymerization between 1,4-diazidobenzene (A1) and tetrakis(4-ethynylphenyl)methane (B1) /2,2',7,7'-tetraethynyl-9,9'-spirobifuorene (B2) (denoted as triazole-A1B1 and -A1B2 gels). The BET specific surface areas of the triazole aerogels are up to 368 m2 g-1. The triazole gels show superior chemical stability, offer the hierarchical porous structure and rich triazole coordination sites for metal nanoparticles immobilization, and can therefore serve as catalyst supports. A range of metal nanoparticles are readily supported in the gels after wet impregnation and reduction. Among them, Ru nanoparticles are anchored within the gel matrix with small nanoparticle size of 2.95 nm. A microfluidic reactor is fabricated by loading [email protected] gel monolith in fused-silica capillary. The triazole-A1B2 gel and [email protected] gel monoliths have high permeability of 2.27 × 10-11 m2 and 1.59 × 10-11 m2, respectively. The [email protected] microfluidic reactor achieves high catalytic activity and selectivity, and ultrafast flow synthesis is developed for the reduction of nitrobenzene derivatives to the corresponding anilines with maximum conversion of 91.8 % and 87.3 % selectivity within 25 s. The reactor shows superior stability and the conversion of nitrobenzene remains above 92 % during 60 h of continuous-flow catalytic reaction. 

Triazole-based covalent gels assembled from small molecules with superior stability for supported catalysis in a monolithic microfluidic reactor

Nickel Nanoparticles Encapsulated in Carbon Nanotubes as an Efficient and Robust Catalyst for Hydrogenation of Nitroarenes

In this work, mesoporous silica SBA-16-supported NiCo bimetallic nanocatalysts were synthesized by coimpregnation of Ni and Co precursors followed by calcination and reduction, and various characterization techniques confirm the formation of NiCo bimetallic nanostructures in the catalysts. The synthesized NiCo/SBA-16 shows enhanced catalytic performance for hydrogenation of a series of nitroaromatics. Under the reaction conditions of 80 °C and 1.0 MPa of H2, the yields of aniline for nitrobenzene hydrogenation over NiCo0.3/SBA-16 can reach more than 99% at 2.0 h. The enhanced catalytic performance can be ascribed to the formation of NiCo bimetallic nanostructures, where the synergistic effect between Ni and Co improves their catalytic activities for hydrogenation of nitroaromatics.

Zhongkui Zhao

Papers

Ni Nanoparticles Grown on SiO2 Supports Using a Carbon Interlayer Sacrificial Strategy for Chemoselective Hydrogenation of Nitrobenzene and m-Cresol