Study On The Catalytic Performance Of Zirconium-based MOFs For The Transfer Hydrogenation Of 5-hydroxymethylfurfural

Biomass resources have attracted much attention in recent years because of their extensive sources and renewable characteristics.2,5-dihydroxymethylfuran,a high value-added polyester raw material,can be prepared by catalytic hydrogenation of 5-hydroxymethylfurfural,a platform compound derived from biomass.The traditional catalytic hydrogenation method usually uses H₂ as hydrogen source,which has the problems of relying on fossil resources,high transportation and storage costs,and flammable and explosive in the use process.It is of great theoretical significance and application prospect to study and develop liquid hydrogen source to substitute H₂ for catalytic transfer hydrogenation.In this paper,a series of Zr-MOFs(UIO-66-X,X=NH₂,NO₂,OH,SO₃H)catalysts were prepared by solvothermal method.The catalytic transfer hydrogenation activity of different functional group ligands for 5-hydroxymethylfurfural was investigated,and the development potential of UIO-66-NH₂ was determined.Then,on the basis of UIO-66-NH₂ as the support,a series of transition metal-supported UIO-66-NH₂ catalysts were prepared by impregnation and reduction method.The effects of the type of transition metals(Ni,Cu,Co)and the loading amount on the performance of the catalysts were investigated.The results showed that 15%Co/UIO-66-NH₂ catalyst had a good catalytic transfer hydrogenation activity.Under the conditions of reaction temperature 100 ^oC,reaction time 4h,nitrogen pressure 2 MPa,isopropanol as solvent and hydrogen donor,92.6%HMF conversion rate and 95.9%DHMF selectivity can be obtained.The activity of the catalyst was not significantly decreased after 5 cycles of reaction,which indicated that the catalyst had good stability.The results of X-ray powder diffraction,X-ray photoelectron spectroscopy,electron microscopy,and temperature-program desorption showed that the addition of cobalt could regulate the acid and base sites of UIO-66-NH₂ to achieve the optimal state of catalytic transfer hydrogenation activity,which was the key to achieve high catalytic activity.In order to further improve the catalytic activity and simplify the synthesis process of the catalyst,transition metal doped UIO-66-NH₂ was prepared by one-step solvothermal method.It was found that the activity of Cu-Co bimetallic doping UIO-66-NH₂ was better than that of single metal doping.The results of optimization of Cu/Co doping amount showed that the best catalytic activity was obtained when the Cu/Co ratio is 4:1(0.8Cu-0.2Co-UIO-66-NH₂).Under the conditions of reaction temperature of 100 ^oC,reaction time of 4h,nitrogen pressure of 2MPa,2-butanol as solvent and hydrogen donor,99.5%HMF conversion and 97.7%DHMF selectivity can be obtained.The activity of the catalyst did not decrease obviously after 5 cycles of reaction,which indicated that the catalyst had good stability.A series of characterization results showed that the increase of acid-base active sites after bimetallic doping and the synergistic effect between copper and cobalt were the main reasons for the high activity.