Application Of Biomimetic Metal-Organic Frameworks(MOFs)in Biomimetic Catalysis And Enzyme Immobilization

In this work,the application of biomimetic metal organic frameworks（MOFs）in catalysis was studied,and the work was carried out from the following four aspects:MOFs with mimic enzyme activity,MOFs modified by small biological molecules,MOFs-enzyme composites and the MOFs based on biomimetic ligands.（1）Mimic enzyme catalysis by MOFs:The mimic lipase activity of Ui O-66 and its two derivatives Ui O-66（NH₂）and Ui O-66（NO₂）,one of the most stable Zr-based MOFs,was investigated.Their activities were investigated from ester hydrolysis,transesterification and esterification reactions,respectively.Ui O-66（NH₂）showed the highest catalytic activity,and analysis shows that Ui O-66 only provided Zr₆ cluster centers,working as Lewis acid.In Ui O-66（NH₂）,however,there are both Zr₆ cluster centers and the amino group centers working as Br?nsted base.The functions of Zr cluster centres and amino moieties observed a synergy effect in Ui O-66（NH₂）as an acid–base catalyst,and the catalytic rate is greatly increased.（2）Modification of MOFs with small biological molecules:Direct coordination modification of proline in a highly stable hierarchically porous MOFs material HP-Ui O-66 was carried out,and the obtained proline-modified MOFs had a good effect in asymmetric catalysis of the Direct-Aldol reaction of p-nitrobenzaldehyde and cyclohexanone.The highest dr value is 80:20,and the highest ee value of trans product is 95%.Direct coordination modification of sulfur-containing amino acids（cysteine and methionine）was also performed wih this highly stable hierarchically porous MOFs.The adsorption behavior of the modified MOFs to Au ions was investigated.Moreover,the materials showed great catalytic activity for hydroalkoxylation of 4-pentyn-1-ol after the modification of Au ions with low concentration,the yield was 88%for Au@HP-Ui O-66-C after 12 h reaction,and about 78%after 5 cycles.HP-Ui O-66-C also showed great catalytic activity for the reduction of 4-nitrophenol after the modification of gold nanoparticles formed from high concentration of gold ions,the k and k_catvalues reached 0.178 min^-1 and 0.0356 mg min^-1,respectively.（3）MOFs-enzyme composites:A highly stable hierarchically porous MOFs HP-DUT-5 was synthesized and used in the immobilization of enzymes.The immobilization capacity of glucose oxidase for HP-DUT-5 was 208 mg g^-1,and the immobilization capacity of uricase was 225 mg g^-1.This method has a large enzyme capacity and improved thermal stability of the enzyme.A glucose colorimetric detector was constructed by immobilizing glucose oxidase and peroxidase on HP-DUT-5,had a detection range of 0～250μM and a limit of detection of 0.2μM.A uric acid colorimetric detector was also constructed with the similar method,had a detection range of 0～100μM and a limit of detection of 0.8μM.Based on this,a hierarchically porous MOFs HP-PCN-224（Fe）,with the activity of mimic peroxidase,was synthesized.HP-PCN-224（Fe）is not only an immobilization matrix,but also a highly efficient mimic peroxidase,which can synergistic catalyze the cascade reaction with the immobilized natural enzyme.An artificial multi-enzyme system with glucose oxidase or uric acid was constructed and applied to the colorimetric detection of glucose or uric acid.For glucose detection,the detection range was 0～300μM and the limit of detection was0.87μM;For uric acid detection,the detection range was 0～100μM and the limit of detection was 1.8μM.（4）MOFs based on biomimetic ligands:2D lamellar metalloporphyrinic biomimetic MOFs material UNs-Co has excellent photocatalytic activity of the oxidation of 5-Hydroxymethyl-2-furaldehyde（HMF）into 2,5-furfural（DFF）after the combination with g-C₃N₄.The HMF conversion of UNs-Co is higher than that of 3D bulk metalloporphyrinic MOFs,including PCN-222-Co and PCN-224-Co.With UNs-Co/g-C₃N₄ as the catalyst,after 10 hours under simulated sunlight,the conversion of HMF was 88.6%and the selectivity of DFF was 85.5%.