Isolated Cu+–O–Ga3+ Pairs as Structural Motifs that Enhance CO2-to-Methanol Conversion

Abstract

Abstract Isolated dual-atom sites constitute a promising yet largely unexplored strategy for directing reaction intermediates in CO2 hydrogenation to methanol. In this work, we identify isolated Cu+–O–Ga3+ dual-atom motifs and provide a mechanistically consistent interpretation linking them to enhanced methanol synthesis. This finding is elucidated through the combined use of steady-state isotopic transient kinetic analysis (SSITKA) with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations. Isolated Cu+–O–Ga3+ pairs, anchored within Cu–Ga–Mg–Al hydrotalcite–derived catalysts, are enabled by ionic-radius compatibility and the preferential Cu+–Ga3+ association within the oxide lattice. X-ray absorption spectroscopy and deep learning-assisted atomic-resolution HAADF-STEM imaging, combined with statistical pair analysis, provide complementary evidence supporting a statistically relevant population of short-range Cu+–O–Ga3+ pairs. Together with the kinetic, spectroscopic, and theoretical analyses, these findings support Cu+–O–Ga3+ proximal motifs as the most plausible structural origin of the enhanced methanol-forming functionality and provide a rational design principle for improved methanol synthesis catalysts.