Interfacial catalysts show considerable potential for the synthesis of multicarbon products from CO2 hydrogenation by leveraging synergistic effects in C═O bond activation and C-C coupling. However, controllably constructing such interfaces under operational conditions remains highly challenging. Here, we engineer a Cu(0)-Co2C interfacial architecture through a reaction-induced reconstruction strategy. During CO2 hydrogenation, Co-Cu oxides are initially reduced to metallic Co(0) and Cu(0), with the K promoter unsealing the in situ carburization of Co(0) to form Co2C. An outside-in carburization mechanism is elucidated and can be manipulated by tailoring the Co(0)-Cu(0) interaction. Compared to Co(0)-Cu(0) bimetals, the optimized Cu(0)-Co2C interfacial catalyst achieves a remarkable leap in C2+ hydrocarbon selectivity from ∼1% to ∼60% while maintaining robust catalytic activity. It delivers a record C2+ yield of 19.4 mmol g-1Co2C h-1 at 300 °C and 3 MPa, outperforming the K-Co2C reference catalyst by a factor of 2.5. The Cu(0)-Co2C interface primarily promotes the CO*-mediated reaction pathways and effectively enhances CH2* coupling. Our findings systematically unravel the dynamic reconstruction mechanisms and interfacial synergy in Co-Cu catalysts, establishing a rational methodology for designing in situ-evolved metal-carbide interfaces to advance CO2 valorization technologies.