In a typical impregnation and chemical reduction procedure, 5.8 mg of Pd(acac)2 was dissolved into 500 l of MeOH with ultrasound and the solution was then added dropwise into 100 mg of NH2-MIL-125 (Ti). The formed slurry catalyst was stirred overnight at room temperature, then filtered and dried at 100 •C for 2 h. Finally, the dried precursor catalyst was reduced by an aqueous NaBH4 solution (2 mL, 0.05 M), and thoroughly washed with deionized water and MeOH. then vacuum drying Afterwards, the sample was put into a vacuum drying at 80 °C for 12 h.