Room temperature synthesis of [Cu(SiF6)(isna)4]n hydrate: a versatile supramolecular porous framework for flue-gas and biogas separation

A new, simple, and environmentally friendly synthesis using water as the main solvent is described to produce [Cu(SiF 6 )(isna) 4 ] n ·hydrate ( 1 , isna: isonicotinamide), a 1D coordination polymer previously obtained unintentionally. The 1D coordination chains in 1 interact through intermolecular forces generating a 3D supramolecular porous framework with channels occupied by water molecules. The present work proves that the activation of this compound can be carried out under relatively mild conditions (333 K and vacuum during 48 h), effectively removing the water inside the channels while preserving the structural integrity and porosity of the material. Water molecules can be further readsorbed when material is exposed to a medium of saturated humidity without causing any significant damage to the crystalline structure, thus denoting significant chemical stability. The adsorption properties of 1 are determined by the presence of narrow bottlenecks of ca. 3.0 Å width, which are present along the porous framework and hinder the uptake of N 2 and Ar at 77 K. Nevertheless, the material is capable of reversibly adsorbing CO 2 , as well as water and methanol vapors, at low pressure. High-pressure adsorption isotherms reveal significant CO 2 /N 2 and CO 2 /CH 4 selectivity, thus placing compound 1 as a promising material for both flue-gas and biogas separations.