Synthesis, Functionalization And Adsorption Properties Of Microporous Metal - Organic Skeleton Materials Based On Meta - Carboxylic Acids

Microporous metal-orgnaic frameworks (MMOFs), as a new kind of inorganic-organic hybrid material, have drawn considerable attention recently due to their structural diversity and tailorable functionalization, etc. They have show potential application in gas adsorption and separation, catalysis, sensors and so on.In this, several MMOFs have been successfully synthesized based on5-ethoxyisophthalic acid or mixed ligands of3,5-dimethyl-1H-1,2,4-triazole and5-R-isophthalic acid(R=H,OH,NH2,OCH2CH3,NHCOCH3), which have been completely characterized by Single-crystal X-ray diffraction, TG, IR. Their gas adsorption and separation properties have been well explored.(1) Using5-ethoxyisophthalic acid (H2eoip) as the ligand and zinc ions as the metal center, a three dimensional MMOFs, namely,[Zn2(eoip)2·H2O]n has been constructed. In this structure, the carboxyl group and zinc ions linked as Rod shaped Secondary Building Unit (SBU), and the ethoxyl groups surrounds as a hexagonal hydrophobic cage. Compared with [Zn(pyip)]n that synthesized by our group, the selective adsorption and separation of water/methanol/ethanol and methanol/acetone azeotropic mixtures were explored. The results suggest that the former MMOFs exhibits Gate Opening effect, the best separation ability of methanol over water or ethanol and interesting separation ability of methanol over acetone.(2) Using the3,5-dimethyl-triazole and1,3-benzyl-dicarboxylate as the mixed ligands, a MMOFs, named as {[Zn5(dmtrz)3(mBDC)3(OH)]-guest}n (MAC-4-A), was constructed by triazole-trimer unit and paddle-wheel unit has been synthesized. The NH2-, OH-, EtO-and NHCOCH3-funcitonalzied IR-MMOFs, named as MAC-4-B, MAC-4-C, MAC-4-D and MAC-4-E, were also isolated through ligand-pre-functionalization strategy. The adsorption ability of CO2and N2were then studied on these five IR-MMOFs, and the results show that the OH-funcitonalized structure shows high capacity of CO2and the better separation ability of CO2over N2.(3) Based on the structure of MAC-4-A, H2OHmBDC, H2NH2mBDC, H2OCH2CH3mBDC, H2NHCOCH3mBDC was mixed with H2mBDC according to the ratio of3:7,5:5,7:3, and four kinds of Ligand-based Solid Solution Frameworks, named as MAC-4-AB-X, MAC-4-AC-X, MAC-4-AD-X, MAC-4-AE-X, was successfully synthesized, and then the adsorption ability of CO2was studied on these MMOFs. The results reveal that only if free volume and specific interactions make a balance, the materials can show the max CO2capacity.