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Zinc Metal–Organic Frameworks Based on a Flexible Benzylaminetetracarboxylic Acid and Bipyridine Colinkers



Three new metal–organic frameworks (MOFs), [Zn2(L)(H2O)]·3DMF·1.5H2O (1), [Zn2(L)(4,4′-bpy)1.5(H2O)2]·2DMF·2H2O (2), and [Zn2(L)(2,2′-bpy)2(DMF)2]·2DMF·4H2O (3) [H4L = 5,5′-(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(azanediyl)diisophthalic acid, 4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine, DMF = N,N-dimethylformamide], were synthesized under solvothermal conditions and characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). The L4– ligands in 13 display different coordination modes, and the introduction of bipyridine colinkers brings significant structural variation into the frameworks. Complex 1 is constructed from dinuclear carboxylate [Zn2O(COO)4] secondary building units (SBUs) and H4L ligands and exhibits a binodal (4,4)-connected pts net with 54.6 % solvent-accessible void. Complex 2 exhibits an unprecedented tetranodal (3,4,4,4)-connected net, which is constructed from two types of crystallographically independent ZnII ions, H4L ligands, and the 4,4′-bipyridine colinker. Complex 3 is constructed from parallel 1D molecular ladders stacked along the a axis that generate 1D channels (7.8 × 10.4 Å) and are hydrogen bonded to form 2D layers. The thermal stabilities and luminescence properties of 13 have also been studied in detail.