To alleviate the intense global warming crisis, developing high-performance photocatalysts for CO 2 reduction reaction (CO 2 RR) to green fuels is of great importance. CsPbBr 3 (CPB) has been proved as a promising photocatalyst for CO 2 RR due to the excellent visible-light response and energetic reduction potential, but its practical performance is still deficient, suffering from severe carrier recombination and poor CO 2 adsorption capability. Herein, we demonstrate novel CPB-nanocrystal-incorporated NH 2 -MIL-125(Ti) (NH 2 -MIL-125(Ti)/CPB) nanoreactors for solar-driven CO 2 RR. Attributed to the optimal conduction band offset (CBO) in the NH 2 -MIL-125(Ti)/CPB heterojunction, excellent carrier transfer is obtained with retained energetic photoreduction potential. Moreover, strong interfacial interaction is demonstrated, enabling the synergistic effect of promoted CO 2 adsorption on NH 2 -MIL-125(Ti) and facilitating interfacial carrier injection. Therefore, greatly enhanced photocatalytic CO 2 RR performance is achieved by as-designed nanoreactors. This work offers a deep understanding into the synthesis of functionalized perovskite-based materials with rationally designed carrier transfer behaviors for not only photocatalytic reactions but also photovoltaic fields.