Polymeric Carbon Nitride Nanosheets as a Metal-Free Heterogeneous Catalyst for Highly Efficient Methanolysis of Polycarbonates

Graphical Here, we have developed an environmentally friendly and cost-effective catalyst for the alcoholysis of C−O-linked plastics. Our catalyst is made of polymeric carbon nitride nanosheets, which are free of metals. It has shown excellent performance in the methanolysis of polycarbonate (PC), polyethylene terephthalate (PET), and polylactic acid (PLA), producing pure monomer products. Through characterization and experiments, we have determined that the amino group is the main active site of the catalyst. Improper end-of-life treatments of C−O-linked plastics have caused serious environmental crises and resource waste. One effective method to solve this issue is the catalytic alcoholysis of these plastics. Traditional homogeneous catalysts or metal-based heterogeneous catalysts for alcoholysis have some drawbacks, such as difficulty in complete separation, environmental threats, and economic burden. Thus, finding a green, low-cost, recyclable, and highly efficient catalyst substitute is critical. Here, we reported that polymeric carbon nitride nanosheets can serve as a metal-free heterogeneous catalyst for the methanolysis of polycarbonate, polyethylene terephthalate, and polylactic acid. The catalyst exhibits remarkable performance and could be reused at least four times. NH x was found to be the predominant active site of the catalyst by characterization and experiments. These results show promise for the design of metal-free heterogeneous catalysts to depolymerize C−O-linked plastics.