Engineering solid-waste-derived Ca-Fe dual functional sorbents-catalysts for integrated CO2 capture and conversion to syngas

Reconstructing dual functional materials (DFMs) from industrial waste such as steel slag offers a sustainable approach to mitigate environmental pollution while valorizing hazardous byproducts. Although the steel slag is rich in calcium and iron, its direct use is hindered by the formation of inactive solid solutions (e.g., Ca 2 Fe 2 O 5 , Ca 2 SiO 4 ), limiting CO 2 capture and conversion performance. In this study, we reconstruct steel slag into a high-performance DFM composed of CaO (adsorptive phase) and FeOx (catalytic phase) for integrated CO 2 capture and utilization (ICCU). The optimized DFM achieves a CO 2 uptake of 9.15 mmol g −1 , a CO yield of 7.80 mmol g −1 , 87 % CO 2 conversion, and 100 % CO selectivity at 650 °C, substantially outperforming the raw slag. Moreover, the DFM maintains outstanding cyclic stability over 10 cycles, with CO 2 uptake ranging from 8.25 to 10.38 mmol g −1 and CO yield from 6.90 to 8.25 mmol g −1 . In-situ XRD and DRIFTS analyses reveal a dual Fe-phase looping mechanism (Fe/FeO and Fe/Ca 2 Fe 2 O 5 ), and a formate-mediated hydrogenation pathway during in-situ CO 2 conversion. This work highlights the untapped potential of industrial waste for developing efficient, sustainable materials for integrated CO 2 capture and utilization.