The Study Of The Single-crystal To Single-crystal Transformation In Metal-organic Frameworks

More and more attentions have been attracted on metal–organic frameworks (MOFs),owing to their potential applications, such as, ion exchange, gas storage, gas separation,magnetism, photology and catalysis. Thereinto, the single-crystal-to-single-crystal (SCSC)transformation in MOFs have got increasing concern.We find a suitable system to investigate the influence of both reaction temperatureand time on the single-crystal-to-single-crystal (SCSC) transformation simultaneously. Inthis work, the centrosymmetric IFMC-68transforms into a chiral IFMC-69doublytriggered by reaction temperature and time simultaneously in the presence or absence ofsolvent. For the first time, we have studied the influence of reaction temperature and timeon SCSC transformation, simultaneously, and get the transformation relationship amongIFMC-68, IFMC-69and the intermediate coming from the direct synthesis method andstepwise synthesis method at different temperatures and for different time. There are thedimerization of Zn4O clusters [Zn4O(CO2)6]2H2O in IFMC-69, and it represents the firstexample that the classic Zn4O(CO2)6SBU connected by water. To our knowledge, it is thefirst representative that the non-interpenetrated structure transforms into a self-penetratedstructure in MOFs. Meanwhile, we have achieved the conversion from an air-unstable to-stable structure. Air-stable IFMC-69exhibits the selective CO2uptake over N2and moreexcellent gas adsorption ability than IFMC-68. In addition, IFMC-69shows an efficientcapability in reversible adsorption of iodine. The electrical conductivity value (σ) ofI2@IFMC-69is much higher than the pristine MOF and thus promising for potentialsemiconductor materials in the future.[(Zn4O)2(L)3]·10H2O·46DMA (IFMC-68)[(Zn4O)2(L)3H2O]·H2O·4DMA (IFMC-69)H4L: methanetetra(tetrakis[4-(carboxyphenyl)oxamethyl]methane acid)We using flexible H4L (methanetetra(tetrakis[4-(carboxyphenyl)oxamethyl]methaneacid)), rigid2,6-naphthalic acid and Zn(NO3)2·6H2O via controling synthesis conditionabtain two metal-organic frameworks. The overall structure of NENU-501is a3D(4,6)-connected network, which is non-interpeneted. While the overall3D framework ofNENU-502can be regarded as a (4,4,5)-connected net, which is interpeneted. Using thestrategy of mixing the flexible ligand and the rigid ligand, we synthesis two MOFs whichcombining the advantage of flexible ligand and the rigid ligand, and effectively getinterpeneted structure by controling synthesis condition, enhancing the stability of crystal.It reveals that differet synthesis conditions can result in differet structures[(Zn4O)(L)(2,6-Naphthalic Acid)]·4H2O·DMF (NENU-501)[(Zn4O)(L)(2,6-Naphthalic Acid)]·7H2O·6DMF (NENU-502)H4L: methanetetra(tetrakis[4-(carboxyphenyl)oxamethyl]methane acid)...