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.