Crystalline to Crystalline Phase Transformations in Six Two-Dimensional Dynamic Metal-Organic Frameworks: Syntheses, Characterizations, and Sorption Studies

摘要

Six dynamic metal-organic frameworks, namely, {[Cd(1,4-bib)(glut)]center dot(4H(2)O)}(n) (1), {[Zn(1,4-bib)-(glut)]center dot(4H(2)O)(n) (2), {[Co(1,4-bib)(3,5-pydc)]center dot(2H(2)O)}(n) (3), {[Mn(1,4-bib)(3,5-pydc)]center dot(2H(2)O)(n) (4), {[Zn(1,4-bib)-(3-mglut)]center dot(4H(2)O)}, (5), and {[Zn(1,4-bib)(2,2'-dmglut)]center dot (2H(2)O)}, (6) from 1-(4-(1H-imidazole-1-yl)butyl)-1H-imidazole (1,4-bib) using four different dicarboxylic acids salt [disodium glutarate (Na(2)glut), pyridine-3,5-dicarboxylate (3,5-pydc), 3-methyl glutarate (3-mglut), 2,2'-dimethyl glutarate (Na(2)2,2'-dmglut)], and four different divalent transition metal ions have been synthesized. Out of these, the structure of compound 3 has been previously reported although synthesized in different method, whereas the rest of the compounds are new. All of these synthesized compounds are characterized by single crystal and powder X-ray diffraction and other physicochemical methods. All the compounds exhibit 2D structure as evident by single crystal X-ray studies. Interestingly, all of these compounds show crystalline to crystalline phase transformation. Variable temperature PXRD study indicates compounds 1 and 6 show single-step phase transformation and the rest show two-step phase transformation upon desolvation. All of these transformations have also been established by IR spectroscopy. Among the structural transformations listed, 1-5 show reversible crystalline to crystalline phase transformation on desolvation and resolvation, whereas 6 shows an irreversible transformation. All of these transformations are thoroughly investigated by PXRD and IR spectroscopy. Sorption studies with CO(2 )and N(2)( )were also performed for all the metal-organic frameworks and characteristic surface adsorptions are found in all the cases.