A new class of three-component photocatalyst system is designed with plasmonic AuCu nanoprisms embedded between a porous single crystalline TiO2 nanoplate thin film and polyhedral zeolitic imidazolate frameworks (ZIF-8) nanoparticles for enhanced CO2 photocatalytic reduction. The ZIF-8 plays a role of CO2 capture to enhance the reactant concentration on the catalyst, while the AuCu nanoprisms function mainly as a mediator to improve the charge density at the interfaces and facilitate the charge transfer to the CO2 adsorption sites on ZIF-8 for subsequent CO2 reduction. The reactant CO2 could be not only readily collected on the newly designed catalyst, but also more efficiently converted to CO and CH4. As a result, compared to the reference sample of two-component system of TiO2 and ZIF-8 with a CO2 conversion rate of 12.5 μmol h−1 g−1, the new three-component photocatalyst exhibited a nearly 7-fold improvement in CO2 photocatalytic reduction performance with CO2 conversion reaching an outstanding value of 86.9 μmol h−1 g−1, highlighting the importance of rational heterojunction design in facilitating reactant adsorption, charge transfer and reaction processes in photocatalysis.