Synergizing Schottky/S‐Scheme Dual‐Junction With Cu/Pb Dual‐Site in a 0D/3D Cu@CsPbBr 3 /g‐C 3 N 4 Heterojunction for Efficient CO 2 ‐to‐C 2 H 4 Photoreduction

ABSTRACT The CO 2 photoreduction to multi‐carbon products, particularly C 2 H 4 , remains challenging due to inefficient charge separation, high C−C coupling barriers, and limited mass transport. Herein, we designed a mixed‐dimensional heterostructure integrating S‐scheme and Schottky junctions, with Cu‐decorated CsPbBr 3 nanocrystals anchored on three‐dimensionally ordered macroporous g‐C 3 N 4 (Cu@CPB/3DOM‐CN). In situ x‐ray photoelectron spectroscopy and femtosecond transient absorption spectroscopy demonstrate dual internal electric fields driving rectified spatial carrier separation with strong redox capability. Strong metal–support interaction induces charge redistribution, generating polarized Cu/Pb dual sites that lower the energy barrier for *CO hydrogenation to *CHO. In situ diffuse reflectance infrared Fourier transform spectroscopy combined with density functional theory calculations provides direct evidence that dual sites promote asymmetric *CO−*CHO coupling. The 3DOM framework functions as a nanoreactor, enhancing the local enrichment of CO 2 and key intermediates to promote coupling kinetics. The optimized catalyst exhibits distinct selectivity across varying CO 2 concentrations, achieving 52.4% C 2 H 4 selectivity (26.37 µmol g −1 h −1 ) in pure CO 2 , which increases to 77.6% and 65.1% under 5% and 0.04% CO 2 (balanced with Ar), respectively, highlighting its remarkable adaptability to diverse application scenarios. This work establishes a triple synergy of directional charge transport, active‐site polarization, and reactant enrichment for efficient and selective CO 2 ‐to‐C 2 H 4 conversion.