Strategies to efficiently activate CO2 by strongly inhibiting the competitive hydrogen evolution reaction process are highly desired for practical applications of the electrochemical CO2 reduction technique. Here, we assembled a core-shell In@InOxHy architecture on carbon black by one-step reduction of NaBH4 as a CO2-to-formate catalyst with high selectivity. The stable CO2-to-formate reaction originates from the creation of steritic frustrated Lewis pairs (FLPs) on the InOxHy shell with In-OVs (OVs, oxygen vacancies) Lewis acid, and In-OH Lewis base. During CO2 reduction, the electrochemically stable FLPs are capable of first capturing and stabilizing protons to protonate FLPs to In-H Lewis acid and In-OH2 Lewis base due to its strong steric electrostatic field; then, CO2 is captured and activated by the protonated FLPs to selectively produce formate. Our results demonstrated that FLPs can be created on the surface of oxyphilic single-metal catalysts efficient in accelerating CO2 reduction with high selectivity.