Unveiling Metal–Support Interactions and Active Cu Sites in CuMgAl Layered Double Oxide Nanostructures for Anaerobic Dehydrogenation of 2,3-Butanediol to Acetoin

Copper-based nanocatalysts excel in the anaerobic dehydrogenation of 2,3-butanediol due to their excellent O–H bond cleavage ability; however, simultaneously enhancing their activity and stability remains a challenge. In this work, we report a robust 7% CuMgAl-LDO catalyst featuring well-defined nanostructures, derived from a CuMgAl hydrotalcite precursor via the coprecipitation method, achieving a 96% 2,3-butanediol conversion and 87% acetoin selectivity. Notably, this engineered nanocatalyst sustained an acetoin yield over 70% for 100 h. Structural characterizations indicated that Cu species were incorporated into the MgAl-LDH framework via the partial substitution of Mg. N2O titration revealed that the 7% CuMgAl-LDO exhibited the highest Cu dispersion (54.6%), which was further confirmed by HAADF-STEM showing a mean Cu nanoparticle size of only 2.3 nm. These structural improvements are attributed to the enhanced metal–support interactions within the nanostructured framework, as evidenced by NH3-TPD and quasi in situ XPS. Mechanistic investigations suggested that the catalytically active phase for anaerobic dehydrogenation likely involved a synergistic effect between Cu+ and Cu0, with DFT calculations further indicating that Cu+ species exhibited superior intrinsic catalytic activity. Furthermore, the enhanced metal–support interactions suppressed the sintering of Cu nanoparticles and prevented the over-reduction of active Cu+ species under a reducing atmosphere, thereby preserving the active phase and promoting the stability of the 7% CuMgAl-LDO catalyst. This study systematically elucidates the metal–support interactions, clarifies the catalytically active phase, and reveals the deactivation mechanism of the 7% CuMgAl-LDO catalyst, providing insights for the design of stable nanostructured Cu-based catalysts.