Syntheses,Properties And Microcalorimetry Of MOFs Based On Host-Guest Interaction

This thesis aims to explore the association of host-guest interactions with metal-organic framework compounds(MOFs)properties.We employ the flexible aromatic carboxylic acid and multidentate compounds with N/O atoms as ligands,Cd(Ⅱ)/Co(Ⅱ)/Pb(Ⅱ)as nodes to construct a series of 3D network compounds.The adsorption/separation,molecular recognition,catalysis and magnetic properties of these synthesized MOFs have been explored,as well as single-crystal-to-single-crystal transformation processes.Employing in situ microcalorimetry,the host-guest behaviors of MOFs in the above processes were monitored online,in order to elucidate the host-guest interaction mechanism and properties optimization of MOFs.The specific contents are as follows:1.We employ 4,4’4’’-triphenylamine tricarboxylic acid as the optical functional ligand,and the Cd(Ⅱ)with d10 electron arrangement as nodes to construct a porous fluorescent Cd-MOF(1).The dynamic structure transformation of 1 can be induced via CH3OH/DMA guest molecules.Using in situ microcalorimetry,the dynamic structure transformation processes of MOFs were monitored online,in order to elucidate the thermodynamic behaviors of the transformation process and provide the theoretical reference for the design of dynamic MOFs.In addition,the cation-driven luminescence properties are studied,and the results show that Cu(Ⅱ)exhibits significant quenching effects compared to the other metal cations,accompanying the color change of the parent MOF because of Cu(Ⅱ)partly instead of Cd(Ⅱ)into compound 2.And we track this process to find that the exchange time is only 9 s via in situ microcalorimetry,thus Cd-MOF can quickly identify Cu(Ⅱ)by naked eye.2.We utilize benzotriazole-5-carboxylic acid to prepared a 3D Co-MOF(3·4H2O),which is liable to undergo structural transformation into 3·EtOH by pore breathing.The dynamic transformation is traced by in situ microcalorimetry to surpport the SC-SC process.We employ the microcalorimeter C80 to research the self-assermbly of MOFs,resulting the new phase at higher temperature,and attained the new compound 4-2DMF.Due to the elongation of the crystal unit via the b axis compared with 3·4H2O5 gas-sorption isotherm experiments demonstrate that the higher CO2 adsorption amounts of 4·2DMF(273 K,99.6 cm3 g-1),while 4·2DMF(125 mg g-1)displays much higher capability for the capture of Cr(Ⅵ)than both 3·4H2O(65 m2 g-1)and 3·EtOH(72 m2 g-1).Moreover,the fitting results of magnetic data show that the value of J2 in 4·2DMF is greater than 3·4H2O,and the energy barrier decreases(Ueff = 59.9 K for 4·2DMF;Ueff=122.6 K for 3·4H2O).The results show that the dynamic transformation of MOFs via the different stimuli can lead to the obvious change of physical and chemical properties.The thermodynamic behavior of the host-guest can help us to understand the dynamic processes,and provide reference for the properties optimization of MOFs.3.A novel Pb-MOF(5)is constructed by using the rich-nitrogen compound 5’-(pyrazin-2-yl)-2H,4’H-3,3’-bi(1,2,4-triazole)as ligand and Pb(Ⅱ)atom with Lewis acidity and high crystal stabilization energy as metal nodes.The large amount of pyrazine nitrogen and triazole atoms in the inner wall of the pore channel is favorable for the adsorption and activation of CO2,and the Pb(Ⅱ)possessing hematospheric coordination mode as Lewis acid catalyst activate the epoxide,the above two catalystic sites can act synergistically the cycloaddition reaction(yields up to 100%,TON up to 800)absent the cocatalyst under the mild environment.The heat of the mixture of epoxides with 5 is measured byin situ microcalorimetry,which can provided the thermodynamics explanation for the catalytic reaction in the confined space.In addition,we also investigated the catalytic performance of 5 on RDX as the main component of solid propellant,and the results show that 5 can effectively decrease the decomposition temperature of RDX by 32 ℃.4.We designed and systhesized a pair of α-alanine derivatives,which were used to constructed a pair of homogeneous chiral 3D Co-MOFs(6-L and 6-D)by self-assembly.The structural analysis shows that there exists the one-dimensional chiral channel via a axis(window size is 11.23 A × 7.72 A),and the chiral carbon atoms and amide nitrogen atoms are evenly distributed in the inner of the channel and towards the center.The enantioselective separation experiments of 6-L/6-D to racemic chiral molecules a-methylbenzylamine,1-phenylethanol and methyl mandelate were studied.For methyl mandelate,the ee value of reaction is up to 77%based on 6-D,and its favorable separation potency may be due to the dual impact of the chirality interaction and confinement effect.The interaction between the chiral framework and the homogeneous chiral substrate was studied by microcalorimetry,reflecting the difference interaction,which is in agreement with the experiment of chiral seParation.The results provide a thermodynamic reference for the design and synthesis of chiral materials with favorable enantiomeric recognition and separation potency.