Direct CO₂ Conversion Using Geological Carbonates as Absorbents for an Integrated Carbon Capture–Conversion Strategy

The current carbon capture and utilization (CCU) technologies suffer from energy-intensive processes due to conventional alkaline-based capture methods requiring significant energy input for regeneration and material cycling. In Earth’s carbonate weathering process within Karst systems, CO 2 is sequestered and transformed through interaction with CaCO 3 . Inspired by this natural process, here, we propose an integrated CO 2 capture–conversion strategy using geologically abundant carbonates as low-cost absorbents. We demonstrate that CO 2 absorbed by carbonates can be efficiently hydrogenated in situ to formate in a one-pot system at 140 °C using a nonprecious cobalt–copper (CoCu) catalyst, achieving 21% yield of formate with diluted CO 2 emissions (as low as 50 000 ppm, representative of typical industrial exhaust). Co facilitates the formation of a Cu + /Cu 0 interfacial structure, leading to an enhancement of the hydrogenation efficiency. Density functional theory calculations show that the Cu + /Cu 0 interface serves as the primary active site for H 2 adsorption and activation to H*, which then promotes the reduction of bicarbonate (HCO 3 – ) to formate. Furthermore, the interface between Co and Cu lowers the energy barrier for HCO 3 – adsorption, leading to its enhanced reduction by H*. This work offers a new pathway for simultaneous CO 2 capture and catalytic conversion, advancing sustainable and energy-efficient CCU technologies.