Fine-tuning of gas uptake and selectivity in a hexafluorozirconate pillared coordination network that features two porous phases

Abstract

Hybrid coordination networks, sustained by divalent transition metal ions and a combination of organic and inorganic linker ligands, are an emerging class of physisorbents for adsorptive gas and vapour capture, especially under trace (≤1%) concentrations. Herein, we report a Cu(II) hybrid coordination network using the anionic pillar hexafluorozirconate ZrF₆²⁻, [Cu(pypz)₂ZrF₆]_n; ZRFSIX-21-Cu (21 = 4-(3,5-dimethyl-1H-pyrazol-4-yl)pyridine). ZRFSIX-21-Cu possesses two ultramicroporous phases, a two-dimensional square lattice phase (α), and a three-dimensional primitive cubic unit phase (β), a rarity among hybrid ultramicroporous materials. Interestingly, ZRFSIX-21-Cu-α revealed better selectivity for C₂H₂ over CO₂, and ZRFSIX-21-Cu-β for C₂H₂ over C₂H₄.