Co(III)-Salen immobilized cellulose nanocrystals for efficient catalytic CO2 fixation into cyclic carbonates under mild conditions

Abstract

Searching for green, recyclable and highly efficient catalyst for the synthesis of cyclic carbonates from CO2 is of great importance because it is profitable for reducing the greenhouse effects and meets the principles of green chemistry. Herein, a series of cellulose nanocrystals, either the pristine or modified ones (TEMPO oxidized and Co(III)salen immobilized), were explored as catalysts for cycloaddition of epoxides and carbon dioxide. The impact of surface properties on the performance of the as-made catalysts was investigated. Co(III)-salen grafted cellulose nanocrystals was proven to be the most effective catalyst in this study, which could afford excellent yield up to 99 % after 24 h even under low CO2 pressures of 0.1 MPa. They can be easily recovered and reused for at least 4 times, demonstrating their excellent stability. We found that the surface functional groups such as enriched sulfate or carboxylic groups could also account for the enhanced catalytic activity. This work highlights the applications of green and sustainable nanoparticles in a cycloaddition reaction and offers a sustainable solution in industrial catalysis related to CO2 conversions.