The First Sulfate-Pillared Hybrid Ultramicroporous Material, SOFOUR-1-Zn, and Its Acetylene Capture Properties.

Hybrid ultramicroporous materials, HUMs, are comprised of metal cations linked by combinations of inorganic and organic ligands. Their modular nature makes them amenable to crystal engineering studies, which have thus far afforded four HUM platforms (as classified by the inorganic linkers). HUMs are of practical interest because of their benchmark gas separation performance for several industrial gas mixtures. We report herein design and gram-scale synthesis of the prototypal sulfate-linked HUM, the fsc topology coordination network ([Zn(tepb)(SO 4 )] n ), SOFOUR-1-Zn, tepb=(tetra(4-pyridyl)benzene). Alignment of the sulfate anions enables strong binding to C 2 H 2 via O⋅⋅⋅HC interactions but weak CO 2 binding, affording a new benchmark for the difference between C 2 H 2 and CO 2 heats of sorption at low loading (ΔQ st =24 kJ mol -1 ). Dynamic column breakthrough studies afforded fuel-grade C 2 H 2 from trace (1 : 99) or 1 : 1 C 2 H 2 /CO 2 mixtures, outperforming its SiF 6 2- analogue, SIFSIX-22-Zn.