Research On The Assembly And Catalytic Properties Of Metal-Organic Cages Based On Functional Ligands

As the novel supramolecular compound,metal-organic cages are prepared from metal ions or metal clusters and functionalized organic ligands by the template assembly strategy.Metal-organic cages,containing specific cavities and modifiable catalytic sites,have become the most potential artificial compounds for simulating enzyme catalysis by mimicking the confined microenvironment and host-guest interaction mechanism of enzyme catalysis.Generally speaking,metal-organic cages can efficiently catalyze various chemical reactions by modifying functional active groups into cage structures or using confined cavities to encapsulate catalysts to form host-guest systems in the field of supramolecular catalysis.In this paper,several novel metal-organic cages with different configurations have been constructed by elaborate coordination assembly of functional organic ligands and metal-centers.Moreover,through researching their host-guest chemistry and catalytic properties,their application in solar energy conversion and imitation of enzyme catalysis has been expanded,which has important practical significance.In the second chapter,two novel metal-organic cubic cages Zn-PAP and Cd-PAP with structural formula M₈L₆ were constructed by using electron-rich polyaniline compounds as tetraamine ligands coordinated with transition metal ions Zn（ΙΙ）and Cd（ΙΙ）,respectively,through the subcomponent assembly strategy.Moreover,the host-guest complex constructed by encapsulating electron-deficient dyes anthraquinone or 9,10-dicyanoanthracene into Zn-PAP has successfully achieved quantitative conversion of photocatalytic reduction of aryl chlorides with high reduction potentials under mild conditions within 30 minutes.Compared with the anthraquinones,the photocatalytic reduction of aryl chlorides showed a 30-fold improvement in the yield by using the host-guest complex of Zn-PAP encapsulated anthraquinones as the catalyst.The artificial photocatalytic system constructed in this chapter makes it possible to activate inert substrates with high reduction potentials in the field of photocatalysis and provides a new idea for the construction of efficient photocatalytic reduction systems.In the third chapter,two zirconium-based metal-organic cages MOCs-1 and MOCs-2 with structural formula M₂L₃ were obtained by self-assembly of the trinuclear zirconium clusters as the metal nodes with the 2-aminobiphenyl dicarboxylic acid ligands and biphenyl dicarboxylic acid ligands modified with reactive squaramide moieties,respectively,and used for homogeneous catalytic Friedel-Crafts alkylation reactions.The results showed that the free squaramide catalyst could prevent the substracte-catalyst recognition due to the harmful self-association of intermolecular hydrogen bond.Incorporation of squaramide moieties into cages by ligand modification can effectively attenuate the detrimental self-association of intermolecular hydrogen bonds in the squaramide catalyst,thereby significantly accelerating the friedel-crafts alkylation reactions between indole andβ-nitrostyrene.This chapter demonstrated that modification of the squaramide moieties into the structure of the cages can effectively prevent their self-association,which is an ideal way to improve and investigate the catalytic activity of the squaramide moieties.