Crystal Phase of TiO ₂ Determines Ni–O–Ti Interface and Enables Nickel Catalysts in Aqueous‐Phase Cyclopentanone Synthesis from Furfural

Abstract Cyclopentanone (CPO) is a high‐value platform chemical widely used in fuel, fragrances, and polymers, yet its sustainable production from biomass remains challenging. This work addresses this gap by developing efficient Ni/TiO 2 catalysts through crystal phase engineering of TiO 2 supports (anatase, rutile, mixed‐phase P25) for aqueous‐phase hydrogenative ring‐rearrangement of furfural (FAL) to CPO. Crucially, the TiO 2 phase dictates the Ni–O–Ti interface structure, governing nickel speciation and reactivity. Ni supported on mixed‐phase P25 achieves exceptional performance under industrially relevant conditions: 91.1% FAL conversion, 89.3% CPO selectivity, and specific rate of 71.6 h −1 , surpassing catalysts on pure anatase (9.1% conversion) or rutile (55.8% conversion). Physical mixture experiments confirm this superiority stems from the intrinsic interface of P25, not component blending. Characterization reveals that P25 stabilizes a multifunctional surface ensemble: metallic Ni⁰ (18.0% by XPS) enables hydrogenation, while cationic Ni 2+ facilitates acid‐catalyzed dehydration and ring rearrangement. Simultaneously, sufficient metal–support interaction permits in situ regeneration of active sites. The optimized 1Ni/P25 demonstrates robust stability over five cycles with retained selectivity (>90%), showcasing practical durability. This study provides a scalable design strategy—support crystal phase tuning—to engineer cost‐effective, multifunctional catalysts for industrial biomass upgrading, advancing green manufacturing of cyclic ketones without precious metals.