Cu(II) MOFs Based on Bipyridyls: Topology, Magnetism, and Exploring Sensing Ability toward Multiple Nitroaromatic Explosives.

In this work, a series of three copper(II) metal-organic frameworks (MOFs), [Cu(4,4'-DP)Cl] (), [Cu(4,4'-DP)Cl] (), and [Cu(4,4'-TMDP)Cl] () (4,4'-DP = 4,4'-dipyridyl, 4,4'-TMDP = 4,4'-trimethylenedipyridyl), is designed and synthesized under solvothermal conditions. Crystallographic investigations reveal that and have tetrahedral and has octahedral environment around the Cu(II) ion. By varying the solvent conditions and ligand derivatives, the topology can be interestingly tuned. TOPOS Pro provides topological conclusions that is stabilized by unusual 2D + 2D → 3D polycatenation of layers lying in (110) and (11̅0) planes with dihedral angle of 90° showing altogether , , and topologies. On the other hand, exhibits a (3,4-c net) topology and shows 4-fold interpenetration with the topology. The dc measurements for - performed on polycrystalline samples in a 0.1 T field confirm strong ferromagnetic behaviors for and and moderate antiferromagnetic behavior for . To examine the sensing properties of the three MOFs, various hazardous nitroaromatic compounds (NACs) were used as analytes. While is a potent fluorescence sensor for highly sensitive detection of multiple NACs, selectively detects -dinitrobenzene (-DNB) with = 5.73 × 10 M and a remarkably lower limit of detection (LOD) value of 1.23 × 10 M. does not show sensing ability toward any NAC probably due to the coordination environment being different from those in and . The work demonstrates fine-tuning of the topology and in turn magnetic and sensing properties by changing the reaction conditions.