Mohmand Numan Zada Khan†, Huirong Ma †, Lianrun Cai†, Jia Wang, Junaid, Qazi Mohammad, Guo-Ying Han*, Dongqi Wang, Lei He, An-Hui Lu*, Xiao Feng*

Cite this article: https://doi.org/10.1016/j.cjsc.2026.101059

Publication date:

Keywords: Metal-organic frameworks (MOFs); Defect; Single atom catalysts; Heterogeneous catalysis; Ethanol dehydrogenation

ABSTRACT

Selective ethanol dehydrogenation to acetaldehyde is a key step in biomass upgrading, yet achieving both high selectivity and activity remains challenging due to competing reaction pathways. Precise catalyst design is therefore essential. Herein, defective UiO-66 was synthesized via formic acid modulation and employed to precisely anchor Cu species, enabling controlled formation of single-atom and multi-atom Cu sites. At low Cu loading, atomically dispersed Cu sites stabilized at defect positions exhibit nearly complete selectivity toward acetaldehyde (≈100%) and an exceptional intrinsic activity of up to 7045 mmol g Cu-1 h-1. In contrast, higher Cu loading leads to the formation of Cu ensembles, which promote secondary reactions, including acetaldehyde coupling to acetone and C4 products, resulting in decreased selectivity. Density functional theory calculations reveal that single Cu sites lower the activation barrier for C-H bond cleavage and weaken product binding, favoring acetaldehyde formation. In contrast, multi-Cu sites induce stronger adsorption and facilitate further transformations. These findings demonstrate that defect engineering in metal-organic frameworks (MOFs) enables precise control over metal nuclearity, providing a rational strategy for designing highly selective and efficient single-atom catalysts.