Single-Crystal-to-Single-Crystal Transformation of a Novel 2-Fold Interpenetrated Cadmium-Organic Framework with Trimesate and 1,2-Bis(4-pyridyl)ethane into the Thermally Desolvated Form Which Exhibits Liquid and Gas Sorption Properties

Abstract

A novel 2-fold interpenetrated, pillared, cadmium metal–organic framework, namely, [Cd(HBTC)BPE]n·nDMF, has been synthesized using 1,3,5-benzenetricarboxylic acid and 1,2-bis(4-pyridyl)ethane (BPE). This compound has been desolvated and subjected to various liquids and gases for sorption studies. Structures of the as-synthesized (1), desolvated (2), and resolvated in benzene (3) have been determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra, and thermogravimetric/differential scanning calorimetry analysis. Single crystal X-ray analysis revealed a 2-fold interpenetrated, three-dimensional (3D) framework which exhibits a 3,5-connected network with the Schläfli symbol of [(63)(69.8) and hms topology. Compound 1 exhibits a temperature-induced single-crystal-to-single-crystal (SC–SC) transformation upon the release of N,N′-dimethylformamide molecules forming compound 2 (stable up to 300 °C). SC–SC transformation is also observed when it is immersed in benzene, chloroform, 1,4-dioxane, and tetrahydrofuran. The uptake of different solvent molecules was analyzed, and desolvated samples selectively adsorb benzene, chloroform, 1,4-dioxane, and THF molecules over other selected polar solvents. Gas (N2, CO2, and N2O) sorption experiments were also performed and the structure showed 2.5% N2, 4.5% CO2, and 3.4% N2O absorption by mass at room temperature and moderate gas pressures (∼10 bar).