Porous coordination networks (PCNs) sustained by inorganic
anions
that serve as linker ligands can offer high selectivity toward specific
gases or vapors in gas mixtures. Such inorganic anions are best exemplified
by electron-rich fluorinated anions, e.g., SiF6
2–, TiF6
2–, and NbOF5
2–, although sulfate anions have recently been highlighted as inexpensive
and earth-friendly alternatives. Herein, we report the use of a rare
copper sulfate dimer molecular building block to generate two square
lattice, sql, coordination networks which can be prepared
via solvent layering or slurrying, CuSO4(1,4-bib)1.5, 1, (1,4-bib = 1,4-bisimidazole benzene) and CuSO4(1,4-bin)1.5, 2, (1,4-bin = 1,4-bisimidazole
naphthalene). Variable-temperature SCXRD and PXRD experiments revealed
that both sql networks underwent reversible structural
transformations due to linker rotations or internetwork displacements.
Gas sorption studies conducted upon the narrow-pore phase of CuSO4(1,4-bin)1.5, 2np, found a high calculated
1:99 selectivity for C2H2 over C2H4 (33.01) and CO2 (15.18), as well as strong
breakthrough performance. Across-the-board, C3H4 selectivity vs C3H6, CO2, and C3H8 was also observed. Sulfate-based PCNs, although
still understudied, appear increasingly likely to offer utility in
gas and vapor separations.