Efficient catalytic transfer hydrogenation of biomass-based furfural to furfuryl alcohol with recycable Hf-phenylphosphonate nanohybrids

An acid-base bifunctional nanohybrid phenylphosphonic acid (PhP) - hafnium (1:1.5) was synthesized through assembly of PhP with HfCl₄ for catalytic transfer hydrogenation of furfural (FUR) to furfuryl alcohol (FFA) using 2-propanol as both reaction solvent and hydrogen donor source. An FFA yield of 97.6 % with formation rate of 9760 μmol g⁻¹ h⁻¹ at 99.2 % FUR conversion was obtained with the reaction system at 120 °C for 2 h reaction time. Activation energy (Ea) was estimated to be 60.8 kJ/mol with respect to FUR concentration, which is comparable with or even lower than Ea values attained over metal catalysts. The pronounced catalytic activity of PhP-Hf (1:1.5) is attributed to its moderate acidity and relatively strong basicity. The PhP-Hf (1:1.5) catalyst was demonstrated to maintain its activity for five consecutive reuse cycles.