Porous Coordination Polymer with Flexibility Imparted by Coordinatively Changeable Lithium Ions on the Pore Surface

Solvothermal reactions of equimolar zinc acetate, lithium acetate, and 1,3,5-benzenetricarboxylic acid (H3btc) in different mixed solvents yielded isostructural three-dimensional frameworks [LiZn(btc)(cG)]·lG [cG and lG denote coordinated and lattice guests, respectively; cG = (nmp)0.5(H2O)0.5, lG = (EtOH)0.5 (1a); cG = H2O, lG = EtOH (1b); nmp = N-methyl-2-pyrrolidone] with one-dimensional channels occupied by guest molecules and solvent-coordinated, extrusive Li+ ions. Thermogravimetry analyses and powder X-ray diffraction measurements revealed that both 1a and 1b can lose all lattice and coordinated guests to form a desolvated phase [LiZn(btc)] (MCF-27, 1) and almost retains the original framework structure. Gas adsorption measurements on 1 confirmed its permanent porosity but suggested a structural transformation from 1a/1b to 1. It is noteworthy that only 1a can undergo a single-crystal to single-crystal (SCSC) transformation into 1 upon desolvation. The crystal structure of 1 revealed that the Li+ i...