Interparticle Porosity Dominated MesoMOFs As Matrix For The Immobilization Of Enzyme And The Performance Evaluation

Metal-organic frameworks(MOFs)have been greatly favored due to its porosity,adjustable pore diameter,high specific surface area and structural diversity.However,the majority of the MOFs are microporous materials,resulting in their application limitation for the immobilization of large molecules such as enzymes and proteins.Interparticles porosity dominated mesoMOFs(IPD-mesoMOFs)are a new class of metal-organic framework material with a mesoporous structure.According to the reported method,two types of IPD-mesoMOFs were synthesized.We choose horseradish peroxidase(HRP)as model enzyme,and the ability of IPD-mesoMOFs for immobilizing enzyme were evaluated.Specific contents are listed as follows:1.Synthesis of IPD-mesoMOF2 and IPD-mesoMOF3IPD-mesoMOF2 and IPD-mesoMOF3 were prepared in ethanol by using nine aluminum nitrate and copper acetate hydrate as central ions,terephthalic acid and trimesic acid as ligands,respectively,in the presence of trimethylolpropane as interparticle-filler.The obtained IPD-mesoMOFs were characterized by X-ray diffraction(XRD),fourier infrared spectrum(FT-IR),scanning electron microscope(SEM).Through the nitrogen adsorption/desorption,specific surface area,pore diameter and pore volume were assessed,the results are consistent with the literature,indicating the successful synthesis of the IPD-mesoMOFs.2.Online immobilization of HRP and quantitative detection of H2O2First,under the condition of static state,by optimizing the pH value,enzyme concentration,stirring time,we preliminary studied the adsorption properties of IPD-mesoMOFs towards HRP.On this basis,the adsorption capacity of IPD-mesoMOFs for immobilizing enzyme was evaluated online by using sequential injection-UV systems as a platform.The SEM and nitrogen adsorption/desorption characterizations showed that the mesoporosity and specific surface area of the IPD-mesoMOFs simultaneously changed after HRP was immobilized,indicating the successful introduction of HRP into the mesopores of the IPD-mesoMOFs.Finally,we used o-phenylenediamine(OPD)as chromogen substrate to test the performance of the immobilized enzyme for H2O2 The IPD-mesoMOFs displayed good linearity against H2O2 concentration in the range of 0.030?1.0 mM with a low detection limit of 6.0?mol/L and 5.0 ?mol/L,respectively.Michaelis constant determination results showed that the activity of the immobilized enzyme was higher than that of free enzyme.The immobilized HRP after being used 30 times and stored for a month still had a high activity,indicating that the as-prepared IPD-mesoMOFs are good carrier for enzyme.