Controlled Uptake And Release Of Iodine In Zn-Base Nanoporous Metal-Organic Framework With Double Walls

In the recent years, a new class of synthetic porous materials, metal–organic frameworks （MOFs） varied in high cavity and different structural properties had been synthesized and characterized. Recent research revealed an emerging interest in host-guest cooperative interactions driven by the encapsulation of guest molecule species into the pores, which leading to the functionalized guest molecule species, host MOFs and novel chemical and physical properties as all.This paper was calculated for tuning the structure and the properties of the MOFs materials with based on previous work with the purpose of functionalizing the MOFs materials. Correspondingly, detailed structural and properties analysis were present. The paper was divided into three chapters:The first chapter introduced the recent progress in MOFs materials detailed in structure category, character and the application. Then the background where this work was based on and the recent progress were reviewed briefly.In the chapter 2, the compound [Zn₃（pybz）₂（lac）₂]·2.5DMF（1·2.5DMF）（pybz = 4-（pyridine-4-yl）benzoic anion, DMF = Dimethylformamide）, was double walls metal-organic framework with a one-dimensional nanoporous channel, ,was prepared from 4-（pyridine-4-yl）benzoic anion and Zn（NO₃）₂·6H₂O under solvothermal condition. The 1D nano-channel （effective window size was 10.2×10.2 （?）²ï¼‰ of the [Zn₃（pybz）₂（lac）₂] （1′） was found running along c axis with a porosity （Vvoid） of 43.5%.The uptake of I2 by 1′in iodine saturated cyclohexane, hexane, benzene, butanol solution was studied by TGA, elemental analysis, sodium thiosulfate titration and UV/vis spectroscopy, the result revealed a solvent dependent I2 uptake amount which was obeyed the sequence of cyclohexane > hexane > benzene > butanol and a fastest I2 loading rate in n-hexane over others. The UV/vis spectroscopy measurement of I2 released by 1′（?） 3I₂ was performed in methanol, ethanol, n-propanol, iso-propanol, n-butanol and sec-butyl alcohol, the release curves were fitted well with zero order kinetic equation in the first hour. The result revealed a solvent dependent I2 release rate: methanol > n-butanol> sec-butyl> ethanol > n-propanol > iso-propanol. UV/vis spectroscopy of I₂ released by 1′（?） 3I₂ in mixed solvents was performed as well. The result showed that the I₂ release rate was slowed down by the use of mixed solvent, while the value was increased when the proportion of the mixed solvent came to the pure one. The over all situations indicated that speed of I₂ released by 1′（?） 3I₂ was hampered by mixed solvents with high chaos degree.In the chapter 3, Zn₃（pybz）₂（gac）₂·nDMF（2·nDMF） was constructed by solvothermal reaction of Zinc（II） nitrate, 2-hydroxyacetic acid（gac） and 4-（pyridin-4-yl）benzoic acid, which was a Nanoporous double-Walls Metal-Organic Framework similar with 1. The 1D nano-channel （effective window size was 12.0 （?）） was found running along c axis with a porosity (V_void) of 46.3 % which was larger than that of 1. TGA and temperature dependent PXRD measurement revealed the thermal stability of 2 was as high as 400 oC. The iodine uptake and released by 2 was performed in n-hexane solvent, where the state of Iodine in solvent and MOFs were evidenced by UV/vis, IR spectroscopy, TGA, Elemental analysis measurements. The result revealed an iodine uptake value of 2.5 I₂ per structural unit, which was less than that of 1′. The UV/vis spectroscopy measurement of I₂ released by 2-I₂ was performed in EtOH, the release curves were fitted well with zero order kinetic equationin the first one hour and ca. 130.7 iodine molecules were released from 1D channel per second. As time going, the release rate became slower and reached the release equilibrium in 3 days finally. As the results suggested, the greater channel diameter or/and the amount of iodine-loading could not guarantee a faster iodine release rate. Known from above, process of I₂ transported between the MOFs and the solvent was complicated by a number of factors which were governed by the host-guest and iodine-solvent interaction and further studies from those aspects were under way.