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• 3DOM structure shows the slow light effect for improving light harvesting efficiency. • Sr component in 3DOM SrTiO 3 enhances CO 2 adsorption and activation properties. • Supported Pt NPs promote the separation efficiency of photogenerated carriers. • Pt n /3DOM-SrTiO 3 catalysts show high activity and selectivity for CO 2 reduction to CH 4. • Surface enrichment of photogenerated electrons and activated CO 2 are rate-determining steps. Herein, we prepared the multifunctional photocatalysts of Pt nanoparticles (NPs)-decorated 3D ordered macroporous (3DOM) perovskite-type SrTiO 3 (Pt n /3DOM-SrTiO 3). The slow light effect of 3DOM photocatalysts improves the absorption of incident light. Surface alkaline-earth-metal Sr component enhances the adsorption and activation for CO 2. Supported Pt NPs can trap and gather excited photoelectrons derived from SrTiO 3 , and Pt-SrTiO 3 heterojunction improves the separation of photogenerated carriers. Pt n /3DOM-SrTiO 3 photocatalysts exhibited high-efficient photocatalytic performance for CO 2 reduction to CH 4 product. Among the catalysts, Pt 2 /3DOM-SrTiO 3 catalyst shows the highest catalytic activity and selectivity, i.e., its formation rate of CH 4 (26.7 μmol g−1 h−1) is 20-fold that of commercial P25, and its selectivity to CH 4 product is 86.7%. The catalytic mechanism for selective CO 2 photoreduction to CH 4 is proposed: the adsorption property for CO 2 and surface enrichment of photoelectrons are two rate-determining steps to improve selectively photocatalytic reduction of CO 2 to CH 4. [ABSTRACT FROM AUTHOR]