Functionalized natural polymers and naturally derived non-polymeric catalysts for CO2 fixation into cyclic carbonates

Global climate change resulting from the emission of carbon dioxide (CO 2 ) is the fundamental challenge facing mankind. Hence, essential approaches for reducing CO 2 emissions, including carbon capture, storage, and conversion into various valuable products, need to be adopted. One of the most effective CO 2 utilization methods includes the cycloaddition of CO 2 into valuable products, such as carbonates, urea, carbamates, carboxylic acid derivatives, and polymers. Among these, the synthesis of cyclic carbonates from CO 2 cycloaddition with epoxides is a significant, atom-economical, and eco-friendly synthesis compared to the conventional process based on phosgene. Moreover, due to their thermodynamic stability, low reactivity, chemical inertness, low energy states, and symmetrical nature, catalysts play a crucial role in activating the conversion of epoxides and CO 2 into cyclic carbonates. Among the different catalysts used, natural polymers have attracted significant attention as sustainable, cost-effective, and eco-friendly alternatives to conventional catalytic systems, due to their biodegradability, abundance, and tunable functional groups. By leveraging their natural structure or grafting active sites onto them, researchers are developing robust and reusable systems that transform waste CO 2 into valuable products with environmental goals. While the main focus of this review is on functionalized natural polymer-based catalysts, naturally derived non-polymeric catalytic systems are also covered to provide a more thorough understanding of renewable catalyst design strategies for CO 2 fixation into cyclic carbonates.