Porous carbon supported Lewis acid-base sites as metal-free catalysts for the carbonylation of glycerol with urea

Glycerol carbonylation is one of the most efficient reaction pathways to utilize glycerol, one of the by-products in biodiesel industry. So far, the vast majority of the reported glycerol carbonylation catalysts contain metals, which are not environmentally friendly. The recent emerging Lewis acid-base chemistry had provided powerful alternatives for metal-free catalysis. Here, we report the facile preparation of the B,N,P co-doped porous carbon materials, and the Lewis acidic/basic defects were detected in their structures. The obtained material BNP@C-800 exhibits excellent catalytic performance for the catalytic carbonylation of glycerol with urea, which achieved up to 93.6% glycerol conversion and 93.7% glycerol carbonate selectivity under metal-free conditions. The catalyst BNP@C-800 could be easily recycled for five times only by simple treatments without obvious loss in catalytic activity. In addition, the key reaction intermediate glycerol urethane was successfully characterized via React-IR spectroscopy. Furthermore, a heterogeneous Lewis acid-base synergistic catalysis mechanism is proposed.