Cu(II) MOFs Based on Bipyridyls: Topology Magnetismand Exploring Sensing Ability toward Multiple Nitroaromatic Explosives

摘要

In this work, a series of three copper(II) metal-organic frameworks (MOFs), [Cu(4,4′-DP)Cl]n (>1), [Cu(4,4′-DP)0.5Cl]n (>2), and [Cu(4,4′-TMDP)Cl]n (>3) (4,4′-DP = 4,4′-dipyridyl, 4,4′-TMDP = 4,4′-trimethylenedipyridyl), is designed and synthesized under solvothermal conditions. Crystallographic investigations reveal that >1 and >2 have tetrahedral and >3 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 >1 is stabilized by unusual 2D + 2D → 3D polycatenation of layers lying in (110) and (1$\bar{1}$0) planes with dihedral angle of 90° showing altogether >fes, >hcb, and >sql topologies. On the other hand, >2 exhibits a >bey (3,4-c net) topology and >3 shows 4-fold interpenetration with the >dia topology. The dc measurements for >1–>3 performed on polycrystalline samples in a 0.1 T field confirm strong ferromagnetic behaviors for >1 and >2 and moderate antiferromagnetic behavior for >3. To examine the sensing properties of the three MOFs, various hazardous nitroaromatic compounds (NACs) were used as analytes. While >1 is a potent fluorescence sensor forhighly sensitive detection of multiple NACs, >2 selectivelydetects meta-dinitrobenzene (m-DNB)with KSV = 5.73 × 10⁵ M^–1 and a remarkably lower limit of detection (LOD) valueof 1.23 × 10^–7 M. >3 does not showsensing ability toward any NAC probably due to the coordination environmentbeing different from those in >1 and >2. Thework demonstrates fine-tuning of the topology and in turn magneticand sensing properties by changing the reaction conditions.