Quaternary ammonium immobilized PAMAM as efficient catalysts for conversion of carbon dioxide

Abstract

Fixation of CO2 with epoxides to generate cyclic carbonates is an essential reaction. The co-catalysts free catalytic conversion of CO2 without metals and solvents is still challenge. Herein, a new series of quaternary ammonium immobilized polyamidoamines (PAMAMs) with hydroxylamino groups were fabricated from reaction of third generation PAMAM dendrimer with glycidyl alkyl dimethylammonium bromide originated from varied tertiary amine with epibromohydrin, which were characterized by FT-IR, TGA, 1H NMR, SEM and XPS, and CO2 adsorption was also observed. These polymers were considered as efficient catalyst for CO2 fixation reaction in the absence of co-catalysts and solvent conditions. Catalytic performances demonstrated that the introduced alkyl groups connected on polymers backbone exhibited crucial effect on catalytic activity, especially, [G3-PAMAM-HADMAB-Cn]Br could effectively catalyzed CO2 fixation with various epoxides under optimized conditions, and corresponding cyclic carbonates can reached at excellent yields. Furthermore, a proposed catalytic mechanism was elucidated on the experimental results and density functional theory (DFT), which indicates that hydrogen bonding play a significant role in activating epoxide and CO2.