Defect-Engineered Cu/AlOx–AlN Catalyst Unlocks Efficient Hydrogenation of Biomass-Derived Aldehydes via Nitrogen Vacancies

Abstract The rational design of support structures is critical to unlocking the potential of non-noble metal catalysts. Although copper-based catalysts are attractive for selective hydrogenation, their intrinsic activity remains modest on typical oxide support interfaces. Herein, we develop a defect-engineering strategy that transforms aluminum nitride (AlN) via controlled hydrolysis into a hybrid AlOx–AlN support, which hosts synergistic nitrogen and oxygen vacancies (Nv/Ov) and stabilizes dispersed Cu nanoparticles. Under mild conditions (120 °C, 1 MPa H2), the resulting catalyst achieves complete conversion of 5-hydroxymethylfurfural (HMF) to 2,5-bis(hydroxymethyl)furan (BHMF) with 99.7% yield, delivering a superior turnover frequency of 37.48 h–1 among non-noble metal catalysts. In situ D2-FTIR detects N–D* species on the support, providing direct evidence for hydrogen migration from Cu to Nv sites. Nv bound hydrogen species, rather than Cu+ sites alone, serve as the primary hydrogenation centers, while a primary kinetic isotope effect (KIE = 3.13) implicates N–H cleavage in the rate-determining step. This work identifies a cooperative catalytic motif in which Cu activates H2 and spillover hydrogen is captured at Nv, decoupling hydrogen activation from substrate binding and providing a generalizable vacancy-engineering concept for non-noble metal catalysts.