Ionic microenvironment constructed in quaternary ammonium modified polyacrylonitrile fiber for efficient CO2 fixation

Fiber-supported quaternary ammonium catalysts for the fixation of CO2 with epoxides were designed and prepared via amination and quaternization of polyacrylonitrile fiber, followed by ion exchange with different anions. The impact of different quaternary ammonium structures and counter anions on the reaction yields was investigated. A fiber catalyst (PANT-UdAF-I) with a C11 carboxylic acid chain and iodide counter anion exhibited excellent catalytic activity in the fixation of CO2 with epoxides under mild and solvent-free conditions (80 degrees C, 0.1 MPa) with a very low catalyst amount (0.5 mol%), and diverse cyclic carbonates were obtained in yields between 24-99 %. PANT-UdAF-I could be conveniently separated by filtration and showed good recyclability and durability till the 4th cycle. Novel cooperative catalytic mechanism is proposed where the ionic microenvironment plays a crucial role to stabilize the ionic intermediates and lowers the activation energy of the reaction.

Automated summary

Quaternary ammonium catalysts supported on fibers, obtained through treatment of polyacrylonitrile fibers, exhibit high catalytic activity and recyclability in the reaction with epoxides, showcasing a novel cooperative catalytic mechanism involving the stabilization of ionic intermediates in an ionic microenvironment.