In Cu–Zn catalysts used for the reverse water–gas shift (RWGS) reaction, Cu and Zn phases remain dispersed, while the Cu–Zn interphase is widely regarded as the catalytically active site. Herein, we engineered a ZnO-decorated Cu-rich Cu–Zn alloy using a mixed Cu/Zn oxalate-based supramolecular metal–organic framework precursor with compositionally homogeneous Cu/Zn mixing. The resulting Cu–Zn catalyst (Cu–Zn|C-oxo|R) maintained >99% CO selectivity and, at 550 °C, delivered a Cu-normalized CO space–time yield (STY) of 1580 mmol(CO) g(Cu)−1 h−1, higher than those of the Cu-only and commercial Cu–Zn–Al benchmarks. Under a high space velocity test, the Cu–Zn|C-oxo|R catalyst remained stable for >50 h at 550 °C. Operando Cu K-edge x-ray absorption spectroscopy shows that Cu is reduced to a predominantly metallic local environment that persists under RWGS conditions. Complementary in situ x-ray diffraction and electron microscopy identify Cu-rich Cu–Zn alloy domains in contact with ZnO, while in situ diffuse reflectance infrared Fourier transform spectroscopy is consistent with an associative formate-mediated RWGS pathway at these interfaces. Density functional theory calculations further revealed that these interfacial sites favor the formate reaction pathway, providing a molecular-level rationale for the enhanced catalytic activity.