Switchable Room‐Temperature Ferroelectric Behavior, Selective Sorption and Solvent‐Exchange Studies of [H3O][Co2(dat)(sdba)2]⋅H2sdba⋅5 H2O

A newly synthesized compound, [H3O][Co2(dat)(sdba)2]⋅H2sdba⋅5 H2O (I, dat=3,5-diamino-1,2,4-triazole; H2sdba=4,4′-sulfonyldibenzoic acid), has Co2 “paddlewheel” units connected by sdba ligands to form one-dimensional chains, which are connected by dat to form an anionic three-dimensional structure with cds topology. The one-dimensional channels in the structure contain water molecules, hydronium ions and H2sdba. The water molecules could be reversibly exchanged with D2O, CH3OH and C2H5OH molecules; these exchanges were performed in a single-crystal-to-single-crystal manner. Gas sorption studies on the dehydrated compound showed the selective adsorption of CO2 over methane at 195 K. Nonlinear optical measurements indicated that I exhibits a second harmonic generation signal that is approximately one-third that of urea. Studies of polarization versus electric field demonstrated compound I as a potential room-temperature ferroelectric material with a saturation polarization of 0.23 μC cm−2 and remnant polarization of 0.14 μC cm−2. The dehydrated compound exhibited a simple paraelectric behavior.