Unleashing CO2-to-olefins conversion via defect-enabled hydrogen spillover in core–shell Fe3O4-FeCx@C catalysts

A pH-tunable metal–phenolic precursor enables uniform core–shell Fe 3 O 4 -FeC x @C. • P123 serves as structure-directing agent and defect inducer to create carbon vacancies. • Active H* may be adsorbed on carbon-defect sites, which suppresses undesirable over‑hydrogenation. • Fe 3 O 4 , Fe 2 C, and Fe 5 C 2 synergistically drive RWGS and C-C coupling to light olefins. • Catalyst achieves 54.95% CO 2 conversion, 45.48% light olefins selectivity, and 100 h stability. The conversion of CO 2 to light olefins via the reverse water-gas shift and Fischer-Tropsch synthesis (RWGS-FTS) tandem pathway offers a sustainable route to value-added chemicals, yet precise control over the catalyst microstructure remains challenging. Here, we report a defect-engineered core-shell catalyst, Fe 3 O 4 -FeC x @C, synthesized from pH-tunable metal-phenolic networks (MPNs) precursor and a P123 soft template. The MPNs ensure uniform dispersion of iron species, while P123 generates abundant carbon defects in the graphitic shell. The resulting Fe 3 O 4 -FeC x @C-P-p2 catalyst features a unique architecture where the core activates H 2 and CO 2 , and the defective shell may promote the adsorption of active hydrogen species, which could spatially decouple active H* from C C coupling. Combined with previous reports, Fe 3 O 4 and FeC x may work synergistically: Fe 3 O 4 could acts as active sites for the RWGS reaction, while FeC x facilitates C C coupling, offering an efficient strategy to boost light olefin selectivity in CO 2 hydrogenation. The carbon shell provides spatial confinement to prevent sintering, while defect sites may promote the adsorption of H*. Under optimized conditions, the catalyst achieves 54.95% CO 2 conversion and 45.48% light olefin selectivity, with no significant deactivation over 100 h. This work demonstrates a synergistic strategy combining defect engineering, hydrogen spillover, and phase cooperation for efficient CO 2 hydrogenation. A defect-rich graphitic carbon shell encapsulates an Fe 3 O 4 -FeC x core to form a core-shell catalyst via a metal-phenolic network (MPN) self-assembly strategy. The defective carbon layers may adsorb spillover active H*, tuning intermediate hydrogenation for higher olefin selectivity. This architecture achieves 54.95% CO 2 conversion and 45.48% light olefins selectivity, with outstanding stability over 100 h, providing a robust platform for efficient CO 2 -to-olefins conversion. Download: Download high-res image (181KB) Download: Download full-size image