A metal-, solvent-, halogen-, and additive-free catalysis for CO2 fixation by carbon dots

Abstract

A simple carbon dots (CDs) catalyst prepared from lignin-derived syringic acid was used for the catalytic fixation of CO₂ with epoxides to synthesize cyclic carbonates. The catalysts exhibited high catalytic performance, and could progress the reaction under metal-, solvent-, halogen-, and additive-free conditions with 1 atm of CO₂ and 80 °C reaction temperature. Various cyclic carbonates could be obtained in high yield and selectivity under these extremely mild catalytic conditions. Additionally, the CDs catalysts showed excellent recyclability with stable catalytic activity. A mechanistic study revealed that the hydroxyl groups on the surface of the CDs are responsible for epoxide activation, and nitrogen-containing sites (graphitic N and pyridinic N) are crucial for CO₂ activation. The cheap precursors, easy and sustainable preparation of the catalyst, and mild and simple operation of CO₂ fixation make the CDs catalyst a promising catalyst for CO₂ conversion.