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

A simple carbon dots (CDs) catalyst prepared from lignin-derived syringic acid was used for catalytic fixation of CO2 with epoxides to synthesize cyclic carbonates. The catalysts exhibited high catalytic performance which can proceed 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 yields and selectivities under the extremely mild catalytic conditions. Additionally, the CDs catalysts showed excellent recyclability with stable catalytic activity. Mechanistic study revealed that the hydroxyl groups on the surface of CDs are responsible for epoxides activation and nitrogen-containing sites (graphitic N and pyridinic N) are crucial for CO2 activation. The cheap precursors, easy and sustainable preparation of catalyst, mild and simple operation of CO2 fixation make the CDs catalyst a promising catalyst for the CO2 conversion.