Water-Stable Metal–Organic Frameworks for Fast\nand High Dichromate Trapping via Single-Crystal-to-Single-Crystal\nIon Exchange

Abstract

Two metal–organic frameworks\n[Zn₂(Tipa)₂­(OH)]·​3NO₃·​12H₂O (<b>FIR-53</b>, FIR denotes\nFujian Institute of Research,\nTipa = tris­(4-(1<i>H</i>-imidazol-1-yl)­phenyl)­amine))\nand [Zn­(Tipa)]·2NO₃·​DMF·​4H₂O) (<b>FIR-54</b>) with large nanotubular channels were\nsynthesized via Zn­(II) ions coordinate the neutral Tipa ligand. The\nframework of <b>FIR-53</b> contains 1D channels along the <i>c</i> axis with a cross section of 18 × 13 Ų. <b>FIR-54</b> also consists of large channels with the 10.5\n× 10.5 Ų open windows. These porous materials\nefficiently trap Cr₂O₇^2– inorganic\npollutant ions via the single-crystal-to-single-crystal (SC-SC) approach.\nThe Cr₂O₇^2– uptake capacities\nof <b>FIR-53</b> and <b>FIR-54</b> are high to 74.2 and\n103 mg/g, respectively. Furthermore, the Cr₂O₇^2– trapping–releasing process of <b>FIR-53</b> displays good regeneration. Meaningfully, the structure of <b>FIR-53</b> after ion exchange can be accurately obtained by single-crystal\nX-ray diffraction, which further elaborates the SC-SC transformation.