Series of solvent-induced single-crystal to single-crystal transformations with different sizes of solvent molecules.

A highly stable soft porous coordination polymer (PCP), namely [Cu3(TP)4(N3)2(DMF)2]·2H2O·2DMF (1), has been synthesized via an in situ synthesis of 4-tetrazole pyridine (TP) under solvothermal conditions (DMF = N,N'-dimethylformamide). Remarkably, the solvent molecules in 1 can be respectively exchanged with cyclohexane (C6H12), cyclopentane (C5H10), decahydronaphthalene (C10H18), 1,4-dioxane (C4H8O2), and tetrahydropyrane (C5H10O) in single-crystal to single-crystal (SCSC) manners to yield [Cu3(TP)4(N3)2(DMF)2]·3C6H12 (1a), [Cu3(TP)4(N3)2(DMF)2]·2C5H10 (1b), [Cu3(TP)4(N3)2(DMF)2]·H2O·C10H18 (1c), [Cu3(TP)4(N3)2(DMF)2]·C4H8O2 (1d), [Cu3(TP)4(N3)2]·3C4H8O2 (1e), and [Cu3(TP)4(N3)2]·2H2O·C5H10O (1f). Further, the occluded cyclohexane molecules in 1a can be removed by heating to give its porous guest-free form [Cu3(TP)4(N3)2(DMF)2] (1g). Particularly, in water, 1 can lose its coordinated N3(-) anions to generate [Cu(TP)2(H2O)4]·4H2O (1h). More interestingly, the soft PCP (1) demonstrates the guest selectivity for the cycloalkane solvents, namely cyclohexane, cyclopentane, and decahydronaphthalene, in SCSC manners for the first time, attributed to the synergy effect between the size and geometry of the solvent and the shape of the framework cavity. Moreover, the desolvated samples of 1e show the highly selective gas adsorption of CO2 over N2, indicating its potential application in the separation of the CO2/N2 mixture.