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Separation of light hydrocarbon mixtures is a very important but challenging industrial separation task. Here, we have synthesized two isostructural cationic metal–organic frameworks {[(Cu(Btz)X]·X·6H2O·0.25DMSO} (FJU-53, Btz = 1,4′-Bis(4H-1,2,4-triazol-4-yl)benzene, X = Cl or Br, DMSO = dimethyl sulfoxide) containing infinite copper-halogen chains and first demonstrated that the adsorption selectivity toward C2/C1 mixtures in the charged MOFs can be improved by tuning counter-anions. FJU-53 exhibits the highest selectivity for C2H2/CH4 separation at 296 K and 1 atm, and exceptional chemical stability in aqueous solutions with pH ranging from 1 to 13. In addition, FJU-53 also shows the attractive solvent- and halogen-dependent thermochromic behaviors. Its thermochromic mechanism is attributed to the thermally induced vibration of the infinite [(CuX)n]n+ chains, remarkably different from that for the traditional copper(II) halide materials, the thermochromism for which comes from the coordination geometry ...

A microporous metal–organic framework (FJU-12), {[Cd12(Trz)8(DMF)2(H2O)4](BDC)9}·2(Me2NH2)·4DMF·16H2O (Trz = 1,2,4-triazole, BDC = terephthalic acid, DMF = N,N-dimethylformamide), was rationally constructed using unprecedented lantern-like 1,2,4-triazole-based dodecanuclear metal coordination cages as supermolecular building blocks. After activation, FJU-12a exhibits highly selective adsorption of C2 compound/CH4 mixtures and efficient sensing of nitrobenzene (NB). The selectivity (79.7) of C2H2/CH4 is comparable to the most selective Cu-TDPAT (82, TDPAT = 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine).