Boron-doped Ni on gradient-pore Al-silica: A highly active bifunctional catalyst for low-temperature hydrodeoxygenation of m-cresol

Upgrading biomass pyrolysis oil via hydrodeoxygenation (HDO) is essential to address its low calorific value and instability from high oxygen content. Herein, we describe a facile aqueous-phase synthesis strategy for fabricating an Al-doped mesoporous silica (Al-MS)-supported B-doped Ni metal-acid bifunctional catalyst (Ni-B/Al-MS) using NaBH 4 as the B source. The Al-MS support, characterized by radially gradient pores (expanding from center to periphery) and tunable acidity, is synthesized in aqueous phase with high yield. B doping (electron configuration 2s 2 2p 1 ) enhances acidity, synergistically modulates the electronic structure of Ni, and optimizes the dispersion and exposure of active sites. Notably, the decomposition of NaBH 4 in aqueous solution generates alkaline conditions, which etch silica to form support defects that act as anchors for metallic Ni. Theoretical calculations reveal that this dual modulation reduces the hydrogen dissociation energy by 27.0 % and the C–OH activation (rate-limiting step) energy barrier by 1.91 eV. Under mild reaction conditions (200 °C, 2 MPa H 2 , 1 h), the Ni-B/Al-MS catalyst achieves near-complete m-cresol conversion (99.5 %) and high methylcyclohexane (MCH) selectivity (91.9 %), outperforming most previously reported systems at substantially reduced reaction temperature and time. This work demonstrates the successful integration of atomic-scale modulation (B doping), mesoscale structural control (gradient-pore support), and bifunctional active sites, providing an effective catalytic strategy for green biomass fuel production and fundamental insights into boron's role in enhancing deoxygenation performance.