Pd immobilized on polymeric network containing imidazolium salt, cyclodextrin and carbon nanotubes: Efficient and recyclable catalyst for the hydrogenation of nitroarenes in aqueous media

Abstract

A novel polymeric network benefiting from the chemistry of imidazolium salt (IL), cyclodextrin (CD) and carbon nanotube (CNT) is fabricated through a multi-step process, in which silica coated CNTs were vinyl functionalized and polymerized with poly (ethylene glycol) dimethacrylate and CD-IL, prepared from the reaction of vinyl imidazole and tosylated CD. The resulting hybrid system, CNT-P, was then used as a support for the immobilization of Pd nanoparticles and furnishing a heterogeneous catalyst, Pd@CNT-P, with the utility for the hydrogenation of nitroarenes in aqueous media. The catalyst exhibited high catalytic activity and selectivity towards hydrogenation of nitro group. Moreover, it was recyclable up to six reaction runs. Comparing the catalytic activity of the catalyst with that of some control catalysts, the contribution of CD-IL and silica coated CNT to the catalysis has been confirmed. It was believed that CD in the backbone of the catalyst could act as a phase transfer agent, while multiple functional groups on the polymeric moiety improved Pd anchoring and suppressed its leaching. Silica coated CNT on the other hand, allowed better dispersion of Pd nanoparticles and assured fine Pd particle size.