The conversion of CO2 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, Fe3O4-FeCx@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 Fe3O4-FeCx@C-P-p2 catalyst features a unique architecture where the core activates H2 and CO2, and the defective shell may promote the adsorption of active hydrogen species, which could spatially decouple active H* from CC coupling. Combined with previous reports, Fe3O4 and FeCx may work synergistically: Fe3O4 could acts as active sites for the RWGS reaction, while FeCx facilitates CC coupling, offering an efficient strategy to boost light olefin selectivity in CO2 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% CO2 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 CO2 hydrogenation.