Photo-induced Dimerization And E/Z Configuration Isomerization Mediated By MOFs Pore Microenvironment

Metal-organic frameworks（MOFs）are a class of porousmaterials constructed by the self-assembly of organic ligands,metal ions or cluster units.MOFs have promising application in selective catalytic organic reactions due to their characteristics of structural and functional diversification,modifiability,tunability,ultra-high porosity,and specific surface area.The precise regulation of the catalytic microenvironment can be achieved by changing the geometry of organic ligands,metal nodes,and modified pores,so as to obtain better regioselectivity and stereoselectivity during the catalytic process.Therefore,the rational design and construction of target MOFs are expected to effectively realize the regio-and stereoselectivity of the reactions.In this dissertation,the photo-induced E/Z isomerization or photodimerization reaction in the pores of MOFs is controlled by regulating the size of the pores.A confined nanoconfinement cage approach is proposed for the generation of mono-or co-encapsulated materials of MOFs to control light-induced competitive reactions.1.A series of MOFs[Zn（sdb）（（E）-X）]_n（（E）-X（?）MOF₁,X=1a-1ab）and[Zn（mbd）（（E）-X）]_n（（E）-X（?）MOF₁’,X=1l,1n,1p-1q,1t,1x-1y,1aa）were synthesized by solvothermal self-assembly of（E）-X guest molecules,Zn（Ⅱ）ions and two"V"-shaped auxiliary carboxylic acids（H₂sdb and H₂mdb）.It can be known that a quadrilateral window unit[Zn₂（sdb）₂]_n whose size is about 8.59×8.53（?）（take（E）-1p（?）MOF₁ as an example）is formed in MOF₁.Only one（E）-X guest molecule is encapsulated in the quadrilateral window.The structure of MOF₁’is similar to that of MOF₁.Due to the different"V"-shaped angles of the auxiliary dicarboxylic acid,the size of the quadrilateral window formed is slightly different.The quadrilateral window of MOF₁’is about 8.36×8.36（?）（take（E）-1p（?）MOF₁’as an example）,it also accommodates only one（E）-X guest molecule.After UV irradiation,the（E）-X guest molecules in the quadrilateral windows of MOF₁ and MOF₁’were transformed from trans configuration to（Z）-X cis configuration,and obtained a series of cis products（Z）-X（X=1a-1ab）.At the same time,the auxiliary dicarboxylic acid after irradiation is recovered for utilization.2.A series of MOFs[Zn₈（bdc）₄（（E）-X）₂]_n（（（E）-X）₂（?）MOF₂,X=1a-1w,1ac-1ai）were synthesized by solvothermal self-assembly of（E）-X with Zn（Ⅱ）ions and a linear auxiliary dicarboxylic acid H₂bdc.Single crystal diffraction analysis showed that MOF₂ is formed quadrilateral window[Zn₈（bdc）₄]_n units with dimension of 10.87×10.96（?）（take（（E）-1h）₂（?）MOF₂ as an example）.A pair of（E）-X guest molecules arranged in head-to-tail fashion are encapsulated in the quadrilateral window.The C=C bond centroid distance is 3.89（?）.After UV irradiation,the（E）-X guest molecules in the quadrilateral window of MOF₂undergo a photodimerization reaction and a series of cycloaddition products Dimer-X（X=1a-1w,1ac-1ai）were obtained.The（E）-X guest molecules with different substituents and positions of the substituents exhibited good substituent tolerance.3.A series of fluorescent MOFs materials MOF₃-MOF₆ were synthesized by solvothermal self-assembly using four different organic molecules with Zn（Ⅱ）ions and H₂oba.Single crystal diffraction analysis showed that MOF₃-MOF₆ had an isomorphic and interpenetrating framework.MOF₃-MOF₆ fluoresced strongly in the solid state and stable suspension of micron-level particles could be obtained by ultrasound.The fluorescence of MOF₃-MOF₆ aqueous suspensions were quenched by folic acid（FA）in a concentration-dependent manner.Fluorescent MOFs test papers could effectively detect FA at micromolar concentrations.