Zn and N co-doped porous carbon nanosheets for photothermally-driven CO2 cycloaddition

Solar energy is considered as the cleanest, cheapest, and most sustainable energy source, and CO2 cycloaddition that is drove by solar energy has unique advantages in the aspect of energy and environmental. Therefore, Zn and N co-doped porous carbon nanosheets (ZNCs), which were synthesized by a simple one-step pyrolysis method, as catalysts and photothermal material to photothermally drive cycloaddition of CO2. The prepared ZNCs show graphene-like layered structure, uniformly distributed Lewis acid (Zn atoms) sites and Lewis base (N atoms) sites, full spectrum absorption and high photothermal conversion efficiency. More importantly, ZNCs have a higher catalytic efficiency than traditional heating methods because it can be quickly in-situ heated by light, hence the yield of cyclic carbonate reached 91.1% (0.1 MPa CO2, 1000 mW·cm−2 full-spectrum irradiation, 12 h). ZNCs were recycled five times without significant reduction in catalytic efficiency, and have high activity to other series of epoxides. A possible CO2 cycloaddition mechanism which is catalyzed by ZNCs is proposed, including the step of adsorption, ring opening, insertion and cyclic carbonates formation.