Design And Synthesis Of Metal-organic Framework Films And Their Application On Separation And Catalysis

Metal-organic frameworks(MOFs)are a class of crystalline polymeric materials consisting of metal ions or metal clusters covalently jointed by organic links which have the advantage of permanent porosity,well-defined open channels,structural diversity and ease of modification.MOFs have a great application in capture,sensing,energy storage,catalysis and separation.We researched structural modification and processing molding of classic MOFs,and prepared chiral D-his-ZIF-8 materials whose skeleton was replaced by the part of D-histidine,MOF-199/Ni film by electrochemical deposition method and BIT-series materials in which POMs are enclosed in the cages of ZIFs.The above methods play a very important role in promoting functional applications of MOFs.Further we explored the performance of the obtained materials and the main research results are as follows:(1)We report a facile yet simple and economically feasible strategy to impart ZIF-8 with absolute bulk chirality through a one-pot approach by ligand in-situ substitution(LIS)with D-histidine.Thus-obtained porous crystalline material(denoted as D-his-ZIF-8)adopts the ZIF-8-like SOD topology,D-histidine and imidazole moieties are most likely randomly distributed in the extended polymeric framework backbones of D-his-ZIF-8.and is imbedded with chiral functionalities.The water stability and inherent chirality of D-his-ZIF-8 enables it efficiently and enantioselectively separate racemic alanine acid and glutamic acid from water/Et OH solution with high enantiomeric excess(ee)value(78.52% for alanine acid,79.44% for glutamic acid).Furthermore,the frameworks can be easily recovered and reused without losing chiral separation activity.In principle,the present method takes advantages of applicable to other MOFs with particular composition or structure type.Moreover,it may open great perspectives in terms of rendering MOFs with new functionalities.This LIS strategy can impart many achiral MOF structures with chiral properties and may expand enantiomer separation into unexplored microporous solid.(2)We prepared MOF-199/Ni film by a convenient and fast electrodeposition method.MOF-199 nanoparticles are tightly anchored on the substrate,with uniform particle size and well accessible pores.Thus electrodeposition method could expand the application in other MOFs.The photocatalytic hydrogen production rate of the MOF-199/Ni film can be increased to 24400 ?mol h-1 g-1 with Pt as co-catalyst,eosin Y as photosensitizer and TEOA as sacrificial agent.To the best of our knowledge,the obtained activity is among the best of all the reported MOF-based hydrogen production systems.Furthermore,compared with powdered catalysts,the film can be repeatedly utilized without substantial loss in hydrogen production activity.Our strategy of coating MOFs containing rich copper unsaturated coordination centers on a porous substrate can be easily generalized and widely applicable to produce new highly active and easy-to-recycle photocatalysts for hydrogen production,and may open up exciting opportunities in a wide range of heterogeneous catalytic systems.(3)We used mechanochemical method and prepared BIT-series compounds in which POMs are embed in the cages of ZIF-8.By changing the proportion of POMs in raw materials,we can get different composite materials with different POMs loadings.Mechanochemical method is a simple,green and efficient synthesis strategy,with low solvent consumption and short reaction time.We researched the proton conductivity of BIT-series materials.Under the conditions of 95% RH% and 90 °C,the proton conductivity of BIT-3(75%)is 1.03 × 10-3 S/cm,which is the highest among these.Materials containing more POMs have better perfermance of proton conductivity than the less ones.The activation energy of BIT-3(75%)was 0.14 e V calculated by the Arrhenius equation.Compared with ZIF-8,after embed POMs,the proton conductivity gave a more than 5 orders of magnitude enhancement at 95% RH% and 90 °C,which demonstrated that the incorporation of POMs exerts a key role in facilitating the internal proton transfer.In subsequent research,implanting mobile protons to design MOFs-based materials with higher proton conductivity,better thermal stability,working under lower humidity or even anhydrous condition is a promising strategy.