Anion-induced structural transformation of a sulfate-incorporated 2D Cd(II)–organic framework

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 C₂H₂ via O⋅⋅⋅HC interactions but weak CO₂ binding, affording a new benchmark for the difference between C₂H₂ and CO₂ heats of sorption at low loading (ΔQ_st=24 kJ mol⁻¹). Dynamic column breakthrough studies afforded fuel‐grade C₂H₂ from trace (1 : 99) or 1 : 1 C₂H₂/CO₂ mixtures, outperforming its SiF₆²⁻ analogue, SIFSIX‐22‐Zn.

Anion-directed assemblies of europium(III) coordination polymers based on 1H-benzimidazole-5,6-dicarboxylate: structures and luminescence properties

Two europium(III) coordination polymers (CPs), namely, poly[[diaquabis(μ₄-1H-benzimidazole-5,6-dicarboxylato-κ⁶N³:O⁵,O^5':O⁵,O⁶:O^6')(μ₂-oxalato-κ⁴O¹,O²:O^1',O^2')dieuropium(III)] dihydrate], {[Eu₂(C₉H₄N₂O₄)₂(C₂O₄)(H₂O)₂]·2H₂O}_n (1), and poly[(μ₃-1H-benzimidazol-3-ium-5,6-dicarboxylato-κ⁵O⁵:O^5',O⁶:O⁶,O^6')(μ₃-sulfato-κ³O:O':O'')europium(III)], [Eu(C₉H₅N₂O₄)(SO₄)]_n (2), have been synthesized via the hydrothermal method and structurally characterized. CP 1 shows a three-dimensional network, in which the oxalate ligand acts as a pillar, while CP 2 has a two-dimensional network based on a europium(III)-sulfate skeleton, further extended into a three-dimensional framework by hydrogen-bonding interactions. The structural diversity in the two compounds can be attributed to the different acidification abilities and geometries of the anionic ligands. The luminescence properties of 1 display the characteristic europium red emission with CIE chromaticity coordinates (2/3, 0.34). Interestingly, CP 2 shows the characteristic red emission with CIE chromaticity coordinates (0.60, 0.34) when excited at 280 nm and a near-white emission with CIE chromaticity coordinates (0.38, 0.29) when excited at 340 nm.