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)(SO4 )]n ), SOFOUR-1-Zn, tepb=(tetra(4-pyridyl)benzene). Alignment of the sulfate anions enables strong binding to C2 H2 via O⋅⋅⋅HC interactions but weak CO2 binding, affording a new benchmark for the difference between C2 H2 and CO2 heats of sorption at low loading (ΔQst =24 kJ mol-1 ). Dynamic column breakthrough studies afforded fuel-grade C2 H2 from trace (1 : 99) or 1 : 1 C2 H2 /CO2 mixtures, outperforming its SiF6 2- analogue, SIFSIX-22-Zn.