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]_<i>n</i>·<i>n</i>DMF, 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 (<b>1</b>), desolvated (<b>2</b>), and resolvated in benzene (<b>3</b>) 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 <i>hms</i> topology. Compound <b>1</b> exhibits a temperature-induced single-crystal-to-single-crystal (SC–SC) transformation upon the release of <i>N</i>,<i>N</i>′-dimethylformamide molecules forming compound <b>2</b> (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)