Molecular Mechanism Of 3d Transition Metal MOF-74 Simulated Peroxidase

Nanozyme is a kind of nanomaterial which can simulate the catalytic function of natural enzyme.Compared with natural enzymes,nanozyme have the advantages of simple preparation,easy regulation of composition structure,low price,high temperature and p H stability,and inherit the optical,electrical and magnetic properties of nanomaterials themselves,so it has become a research hotspot of chemistry,biology and environment.So far,more than 1200 different nano-enzyme materials have been reported to have catalytic functions of dozens of biological enzymes such as peroxidase,catalase,superoxide dismutase,oxidase and glucose oxidase.Among them,peroxide-like nanozyme can transform low oxidizing H₂O₂ into high oxidizing HO·or monatomic oxygen,and then oxidize reducing substrates with obvious chromogenic phenomenon.Therefore,they have been widely concerned for their important applications in biosensing and immunoassay.However,the catalysis mechanism of most nanozyme is unclear,and the low catalytic activity and poor substrate selectivity are the main challenges facing the research and application of nanozyme.The development of activity descriptors that can be used for rational design and optimization of nanozyme is an urgent problem in this field.Based on a large number of samples of nanomaterials with similar composition and structure,systematically studying the mechanism and structure-activity relationship of the peroxidase activity of nanomaterials is an effective way to further study the enzymatic catalysis principle of nanomaterials.MOF-74,a special family of metal-organic framework MOF,can form stable complexes with different metals due to its high pore volume and abundant coordination unsaturated sites,and has relatively good stability in low temperature and water environment,which provides an excellent sample library for systematic study of the simulation of the molecular mechanism of peroxidase and the structure-activity relationship.In this paper,the 3d transition metal MOF-74 is taken as the research object.Firstly,the changes of its electronic structure in ground state,band gap,d band neutral and other internal physicochemical properties with the change of metal are studied,and the stability of the material in water is also investigated.Secondly,the molecular mechanism of the model to simulate peroxidase activity was systematically studied.The activity prediction descriptor was summarized and its intrinsic physical image was explained.The accuracy of the prediction model was verified by experiments.Finally,the specificity of the catalytic direction was further studied from the perspective of thermodynamics.The following main results were achieved:1)The order of water stability of 3d metal MOF-74 is V>Mn>Fe>Cr>Ni>Zn>Co>Cu;2)The theoretical and experimental results showed that Co-MOF-74 had the best peroxidase activity;3)The electron occupancy number of e_g can be used as a descriptor to predict the peroxidase activity of 3d metal MOF-74.When the electron number of e_g is 1.58,the material has the best peroxidase activity.4)When OH adsorbed E_ads,OH<-3.0 e V,H₂O₂ tended to mutate to O₂,showing catalase activity;When E_ads,OH>-3.0 e V,H₂O₂ tends to decompose into OH radical,showing peroxidase activity.The above results are the first systematic study on the activity and selectivity mechanism of 3d metal MOF-74 peroxidase at the molecular and atomic level.It was found that e_g electron occupancy number could be used as a descriptor for predicting the activity of 3d metal MOF-74 peroxidase,and the prediction accuracy was verified by experiments.The results provide a theoretical tool for predicting the activity of other MOF-74 enzymes.