Tea saponin-derived porous carbon bearing rich oxygen-containing groups towards high efficient CO2 fixation

The effective utilization of biomass resources can bring significantly environmental and economic benefits. In this context, tea saponin, which can be easily and extensively extracted from the oil cake as the biomass waste during the seed oil production from camellia seeds, is explored as the precursor to synthesize porous carbon bearing abundant –OH and –COOH groups via a simple carbonization process. Owing to the obtained porous structure and existence of rich oxygen-containing groups serving as Lewis acidic sites, the carbonized tea saponin (CTS) can display impressive catalytic activities for CO2 cycloaddition reaction with both high selectivity (> 99%) and high yield of target cyclic carbonate under either thermally driven (80 °C and 0.1 MPa CO2) or photo-thermally driven (UV-Vis light irradiation with the light intensity of 350 mW/cm2) conditions. In addition, benefiting from the good chemical stability, CTS can be reused for many cycles with almost no catalytic activity loss, making CTS a promising biomass-based catalyst for CO2 fixation under mild conditions.