Cu<sup>II</sup> Coordination Polymers Capable of Gelation and Selective SO<sub>4</sub><sup>–2</sup> Separation

A crystal engineering rationale has been exploited to generate a series of Cu<sup>II</sup> coordination polymers namely [{Cu­(μ-<b>L1</b>)­(SO<sub>4</sub>)­(H<sub>2</sub>O)<sub>3</sub>}·H<sub>2</sub>O]<sub>∝</sub> <b>CP1</b>, [{Cu­(μ-<b>L1</b>)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>}­F·2H<sub>2</sub>O]<sub>∝</sub> <b>CP2</b> [{Cu­(μ-<b>L1</b>)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>}­Cl·H<sub>2</sub>O]<sub>∝</sub> <b>CP3</b> and [{Cu­(μ-<b>L1</b>)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>}­Br·H<sub>2</sub>O]<sub>∝</sub> <b>CP4</b> derived from N, Ń-(3-pyridyl) m-phenyleneurea (<b>L1</b>) capable of gelling aqueous solvents (DMF/water); in situ crystallization of <b>CP1</b> has been exploited to separate SO<sub>4</sub><sup>2‑</sup> anion selectively from a complex mixture of oxo anions (SO<sub>4</sub><sup>2–</sup>, NO<sub>3</sub><sup>–</sup>, ClO<sub>4</sub><sup>–</sup>, CF<sub>3</sub>SO<sub>3</sub><sup>–</sup>). 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.