Fluorescent cadmium(ii) metal–organic frameworks exhibit excellent stability and detection ability to Fe ³⁺ and MnO ₄ ⁻ ions

Abstract

Cd-MOFs constructed from carboxyl-decorated tetrapoda ligands feature remarkable stability and luminescence property and can be suggested as a selective fluorescence sensor for detecting Fe ³⁺ and MnO ₄ ⁻ ions.

Abstract

Two new 3D Cd( ii)-MOFs have been constructed from a tetrakis(4-carboxybiphenyl)ethylene ligand, namely [Cd _4.25(tcbpe) ₃]·0.25(C ₄H ₁₁N)·7.5DEF (NLMOF-1) and [Cd ₂K(H ₂tcbpe)(Htcbpe)] _n ·4DEF (NLMOF-2). Single-crystal X-ray analysis revealed that NLMOF-1 is of 3D framework constituted by 1D metal chains containing six-nuclear secondary building units (SBUs) and one-dimensional channel, while NLMOF-2 also exhibits a 3D structure in which the 1D channel is blocked by coordinated K ions, resulting in poor chemical stability. NLMOF-1 possesses excellent stability in both water and common organic solvents, conducive to investigating its utility as a chemical sensor. Fluorescence sensing studies show that NLMOF-1 is characteristic of highly sensitive and selective quenching effects toward Fe ³⁺ ions in DMF, DMA, and acetonitrile, as well as MnO ₄ ⁻ ions in H ₂O, DMA, and acetonitrile. The above results suggest that NLMOF-1 can be considered a potential fluorescent sensor for detecting Fe ³⁺ and MnO ₄ ⁻ ions.