Breaking the Activity–Selectivity Trade-off in Low-Temperature CO2 Hydrogenation: Spatial-Electronic Dual Regulation via Ca-Doped Core–Shell Catalysts for Efficient Methanol Synthesis

To address the challenging trade-off between activity and selectivity in low-temperature hydrogenation of CO2 to methanol, this study employs a nanoreactor design strategy to construct a Ca-doped Cu-based core–shell catalyst (CZ@Cu5Ca2Zn0.375). Under a low temperature of 200 °C, 5.0 MPa, and gas hourly space velocity (GHSV) = 9000 mL·gcat–1·h–1, this catalyst achieves a CO2 conversion rate of 8.8%, methanol selectivity of 92.0%, and a space–time yield (STY) of 252.8 g·kg–1·h–1. Ca doping introduces moderate basic sites and enhances the adsorption of CO2 by utilizing the alkaline nature of Ca, thereby improving the surface utilization efficiency. Simultaneously, the core–shell structure preserves the integrity of the hollow sphere and provides a spatial confinement effect that increases local methanol concentration, facilitating its autocatalytic role in methanol synthesis. The synergistic integration of the Ca-based outer shell and the hollow core promotes CO2 adsorption, strengthens the autocatalytic pathway, and suppresses side reactions. This cooperative design effectively breaks the traditional activity–selectivity trade-off and offers a strategy for low-temperature, efficient CO2-to-methanol conversion.