Solid-state structural transformation doubly triggered by reaction temperature and time in 3D metal-organic frameworks: great enhancement of stability and gas adsorption

In this work, we have demonstrated an unprecedented single-crystal-to-single-crystal (SCSC) transformation between two 3D metal-organic frameworks (MOFs). The centrosymmetric IFMC-68 ([(Zn4O)(2)(L)(3)]center dot 10H(2)O center dot 46DMA) transforms into a chiral IFMC-69 ([(Zn4O)(2)(L)(3)H2O]center dot H2O center dot 4DMA) doubly triggered by reaction temperature and time simultaneously in the presence or absence of solvent. To our knowledge, this is the first representative that the non-interpenetrated structure transforms into self-penetrated structure in MOFs. For the first time, we have studied the influence of reaction temperature and time on SCSC transformation, simultaneously, and get the transformation relationship among IFMC-68, IFMC-69 and the intermediate coming from the direct synthesis method and stepwise synthesis method at different temperatures and for different times. Meanwhile, we have achieved the conversion from an air-unstable to air-stable structure. Air-stable IFMC-69 exhibits the selective CO2 uptake over N-2 and more excellent gas adsorption ability than IFMC-68. In addition, IFMC-69 shows an efficient capability in reversible adsorption of iodine. The electrical conductivity value (sigma) of I-2@IFMC-69 is much higher than the pristine MOF and thus is promising for potential semiconductor materials in the future.