Cu^II Coordination Polymers Capable of Gelation and Selective SO₄^–2 Separation

A crystal engineering rationale has been exploited to generate a series of Cu^II coordination polymers namely [{Cu­(μ-L1)­(SO₄)­(H₂O)₃}·H₂O]_∝ CP1, [{Cu­(μ-L1)₂(H₂O)₂}­F·2H₂O]_∝ CP2 [{Cu­(μ-L1)₂(H₂O)₂}­Cl·H₂O]_∝ CP3 and [{Cu­(μ-L1)₂(H₂O)₂}­Br·H₂O]_∝ CP4 derived from N, Ń-(3-pyridyl) m-phenyleneurea (L1) capable of gelling aqueous solvents (DMF/water); in situ crystallization of CP1 has been exploited to separate SO₄^2‑ anion selectively from a complex mixture of oxo anions (SO₄^2–, NO₃^–, ClO₄^–, CF₃SO₃^–). While the gels are characterized by optical-, scanning electron microscopy and rheology, structure–property (gelation, as well as anion separation) correlation has been attempted by using single crystal- and powder-X-ray diffraction data.