Green Piezo-Photocatalytic Oxidation of HMF to DFF Over Mn-Doped Zr/Hf-Based UiO-66 Frameworks Under Mild Conditions

Developing energy-efficient strategies for converting biomass-derived platform chemicals remains critical for sustainable chemistry. Efficient conversion of biomass-derived 5-hydroxymethylfurfural (HMF) to high-value 2,5-diformylfuran (DFF) remains challenging due to energy-intensive processes and poor selectivity. Here, we developed a novel Mn-doped bimetallic UiO-66(Zr/Hf)-NH₂ piezoelectric photocatalyst via solvothermal synthesis. The optimal 3Mn/UZH0.5 catalyst (Zr/Hf = 1:1, 3.10 wt% Mn) achieves 81.3% HMF conversion and 68.9% DFF yield with 84.8% selectivity within 2 h, delivering high productivity (1377.8 μmol g^-1 h^-1) under mild conditions, while maintaining >75% selectivity over 5 cycles. Mechanistic studies reveal that ultrasound-induced piezoelectric fields suppress electron-hole recombination, while Mn³⁺/Mn⁴⁺ redox cycling and dominant reactive oxygen species (·O₂ ^- and ¹O₂) enable selective HMF oxidation. This work establishes a green catalytic platform using simultaneous solar/mechanical energy for biomass upgrading, advancing circular bioeconomy goals.