Peroxidase-like Activity Of Transition Metal-Organic Frameworks And Its Application

Natural enzyme is an important biocatalyst with high catalytic activity and high selectivity,which is widely used in all kinds of biochemical detection.However,it has some disadvantages such as easy inactivation and high price.Development of artificial enzymes with catalytic activity similar to natural enzymes is one of the ways to solve this problem.Metal-organic frameworks(MOFs)are a kind of porous crystalline materials that are self-assembled by coordination of a metal or metal cluster with an organic ligands.They have attracted much interest in mimics enzyme due to their large specific surface area,adjustable pore size,modifiable channel environment,good thermal stability and so on.At the same time,the transition metal MOFs are ideal materials of artificial enzyme because the transition metals can be used as catalytic reaction activity center.In this paper,transition metal-organic frameworks were successfully synthesized under mild solverthermal by optimization of material ratio between metal ions and ligands.The catalytic properties of its mimic enzyme and structure-activity relationship were also studied.It provides a new idea and theoretical foundations for detection of biomolecules with high activity and selectivity.The specific research content is as follows:1.Two MOFs,[Cu₃(BTC)₂(H₂O)₃](1),[Cu₂(BPTC)₄(H₂O)₂](2),were constructed by employing rigid aromatic carboxylic acid[1,3,5-benzenetricarboxylic acid(H₃BTC),3,3',5,5'-biphenyl tetracarboxylic acid(H₄BPTC)]assemble with copper ions respectively,which were characterized by X-ray single crystal diffraction,X-ray powder diffraction,infrared spectroscopy and thermogravimetric analysis and so on.[Cu₃(BTC)₂(H₂O)₃](1)belongs to the cubic crystal system,F_m-3m space group.The central copper ions connect with one water molecule and four oxygen atoms from different 1,3,5-benzenetricarboxylic acid,respectively,forming a 5-coordinated pyramidal configuration.The sub-units are spatially connected by linkers to form a periodic three-dimensional network structure.[Cu₂(BPTC)₄(H₂O)₂](2)belongs to a trigonal system,the R-3 spatial group.The central copper ions also connect with one water molecule and four oxygen atoms of carboxylic acid from different ligands,respectively,forming a 5-coordinated pyramidal configuration.The differences are that each BPTC in compound 2 has four carboxyl groups,and connect four secondary structural units to form a 3D reticularis structure.Compounds 1 and 2 showed ideal mimic enzyme activity to catalyze H₂O₂to generate·OH radicals that oxidize colorless substrate(TMB)to blue oxidized products(ox TMB).In additional,the structure-activity relationship was investigated between peroxidase-like activity with Langmuir specific surface area as well as pore structure.2.Two novel MOFs,[Cu(PDA)(DMF)](3),[Fe(PDA)₂](4),were constructed by pyridine carboxylate acid[1,10-phthalazophil-2,9-dicarboxylic acid(H₂PDA)]with iron nitrate and copper nitrate respectively.[Cu(PDA)(DMF)](3)belongs to the triclinic system,P-1 space group.The central Cu cation is chelated to the N and O atoms of the ligand,while the two asymmetric structural units are connected with each other via carboxyl groups to form a central symmetrical twin structure,which is further connected via?-?interactions to form a 3D supramolecular structure.[Fe(PDA)₂](4)belongs to tetragonal crystal system,I4₁/a space group.The central Fe cation is chelated to two H₂PDA to form a twisted dodecahedral coordination conformation,while the adjacent units are connected by?-?interactions to form a three-dimensional supramolecular structure.Compound 3 showed ideal peroxidase-like activity.Based on the peroxidase-like activity of compound 3 and DA-induced inhibitory effect,a sensitive and selective strategy is developed for colorimetric detection of DA.Compound 4 also showed better peroxidase activity.When the molar concentrations of[Fe(PDA)₂]and Fe(NO₃)₃·9H₂O are all 0.2 mg mol^-1,[Fe(PDA)₂]exhibited a more excellent analog enzyme catalytic properties than the free Fe³⁺.3.A ZIF-8@ZIF-67 nanododecahedral composite precursor(imidazole type)with core-shell structure was synthesized by liquid-phase diffusion method.After high temperature thermal treatment,the nitrogen-containing imidazole organic ligand was carbonized in situ into a carbon with dodecahedral structure.Meanwhile,the organic ligand was transformed into carbon nanosheets,which were further curled into carbon nanotubes under the catalytic action of Co nanoparticles,consequently forming carbon intermediate of nanotube@nandodecahedron coated Co nanoparticles.The Se source was then introduced by chemical vapor deposition the Se source was then introduced by chemical vapor deposition which made the Co nanoparticles transform into Co_xSe_ynanoparticle,forming carbon nanotubes@nanododecahedron-coated Co_xSe_ynanoparticle composites.A series of unique Co Se₂,Co_0.85Se catalysts with novel composition were synthesized.Both composite materials showed ideal mimic enzyme activity.By comparing the steady-state dynamics of the two composite materials,it was found that Co_0.85Se has higher peroxidase-like activity than Co Se₂.