Syntheses, Crystal Structures And Properties Of Metal-Organc Frameworks Based On Triazole Clusters

Cluster-based metal-organic framework self-assembled from polynuclear metal clusters SBUs have potential applications in adsorption, separation, sensor devices and proton conductivity. Though MOFs have advantages in structural design and performance regulation, they have low stability making it difficult to locate the adsorption site of guest molecules, thus it is difficult to explain the internations between host-guest from the molecular level. In addition, MOFs formed by high-nuclearity metal clusters help to avoid structural interpenetration and improve framework porosity, but the MOFs showing permanent porosity and high adsorption capacity are rare, so design and synthesis of MOFs based on high-nuclearity cluster with permanent porosity have been challenging. In this thesis, we obtain eight new MOFs constructed by 1,2,4-triazole and carboxylic ligands, and five interesting frameworks on the basis of compound 2.Compound 2 ([Zn(Trz)(NH2BDC)1/2]·DMF·(H2O)1/2) shows high water and thermal stability by intramolecular hydrogen bonding. This is the first observation of MOFs with improved stabilization by intramolecular hydrogen bonding of organic bridging ligands. In addition, we lacate the adsorption sites of CO2 by single X-ray diffraction successfully. It was found that different cages (Cage-Ⅰ, Cage-Ⅱ) in 2 can selective recognition CO2 molecules with different concentrations. When CO2 concentration is high (pure CO2, CO2/N2= 15/85), Cage-Ⅰ and Cage-Ⅱ can both capture CO2 molecules. But when decreasing CO2 concentration to 400 ppm, only Cage-Ⅰ is loaded with CO2 molecules. This is the first observation of CO2 capture from air on a pillared Metal-Organic Frameworks, providing supplementary for adsorption mechanism between CO2 molecules with host framework and is of great significance for rational design of MOFs.Compound 7 is constructed by high-nuclearity metal cluster SBU, that is dodecanuclear metal coordination cage, [Cd12(Trz)8(Osolvent)6(CO2)18]. Compound 7 not only shows permanent porosity, but also has good selective adsorption towards C2s/C1, especially for C2H2/CH4 with selectivity of 79.7 comparable to highest one 82 (Cu-TDPAT).