Synthesis And Applications Of MOFs In Hydrogenation And Drug Delivery

Metal-organic frameworks（MOFs）are a kind of new porous materials with high specific surface area,excellent thermal and chemical stability,and adjustable size structure composed of organic multidentate ligands and inorganic secondary structure units.During the past two decades,MOFs have been widely applied in the fields of catalysis,drug delivery,gas storage and separation,and chemical sensing.As catalyst supports,MOFs are one of the promising new catalytic materials because of their atomic-level metal nodes and ligand functional groups.In the field of biological applications,MOFs are also excellent drug carriers which can control release rate of drugs in organisms.In this paper,zirconium tetrachloride,1,4-terephthalic acid,N’,N-dimethylformamide（DMF）and chloroplatinic acid were utilized to synthesize the Pt/Ui O-66 catalyst with regular octahedral structure via a one-pot method.Characterization showed that the specific surface area of Pt/Ui O-66 catalyst was as high as 1197 m²·g^-1 and the pore size distribution was centralized at 0.80 nm and 1.19 nm.Sub-nanometer Pt was uniformly dispersed in pores of Ui O-66.In addition,Nitrobenzene hydrogenation was regarded as a model reaction to explore the effect of synthesis temperature of Pt/Ui O-66 and the reaction conditions.It was found that the conversion of nitrobenzene was as high as 96.1%at room temperature under 20 bar H₂,the selectivity of aniline was 93.8%,and the turnover frequency（TOF）of Pt reached 21352 h^-1.Moreover,this catalyst has wonderful activity and stability for the hydrogenation of nitro compounds with different substituents.We found that Pt/Ui O-66 catalyst also had excellent activity and selectivity for more complex selective hydrogenation of C=O bonds inα,β-unsaturated aldehydes.Therefore,a detailed comparison for cinnamaldehyde hydrogenation between solvent transfer hydrogenation and traditional molecular H₂ hydrogenation was carried out.It was indicated that some kinds of protonic solvents could not only supply hydrogens to unsaturated aldehydes,but also have higher selectivity for cinnamyl alcohol.Under 150℃in isopropanol,the conversion of cinnamaldehyde was 90.5%,the selectivity of cinnamyl alcohol was maintained above 94.6%,the utilization of isopropanol acting as hydrogen donor reached 92.6%and the TOF was as high as 4071 h^-1.However,in traditional hydrogenation process with molecular H₂,the selectivity of cinnamyl alcohol was only 72.8%.At the same time,we also compared the differences between transfer hydrogenation and molecular H₂ hydrogenation process for citral,citronellal,5-hydroxymethyl furfural and other 7 kinds ofα,β-unsaturated aldehydes over Pt/Ui O-66 catalyst.Results showed that the selectivity of C=O bonds was higher via transfer hydrogenation.Finally,we synthesized the core-shell material（M-ZIF-8）coated with montmorillonite（MMT）via a one-pot method.After loading with anti-inflammatory drugs（Drug@M-ZIF-8）,this material could be delivered to the body by oral administration.It was found that the decomposition rate of Drug@M-ZIF-8 in gastrointestinal tract could be delayed under the protection of MMT shell.Compared with Drug@ZIF-8 without shell material,the complete release time of Drug@M-ZIF-8 in acidic environment of stomach was extended from 24 h to 60 h,while in alkaline environment of intestinal tissue was extended from 120 h to 240 h,which greatly improved the drug bioavailability.