SnO2 nanoparticles are supported over graphitic carbon nitride (g-C3N4) via a simple precipitation method and it efficiently catalyzes the reaction of CO2 and ethylenediamine to form 2-imidazolidinone, achieving 95% conversion and 99% selectivity at 160 °C and 2.5 MPa in 2 h. The catalyst exhibits excellent recyclability, providing a sustainable and cost-effective route for cyclic urea synthesis and CO2 utilization.