Selective luminescent sensing of metal ions and nitroaromatics over a porous mixed-linker cadmium(ii) based metal–organic framework

Abstract

A potential luminescent sensor, based on porous metal organic framework (MOF) for the detection of metal ions (Al³⁺, Fe³⁺ or Cr³⁺) and nitro explosive, 2,4,6-tri-nitrophenol (TNP) has been identified. The cadmium(II) containing mixed-linker MOF viz. {[Cd(L₁)(L₂)](DMA)}_n (L₁ = 2-amino-1,4-benzenedicarboxylate, L₂ = 4,4′-azopyridine and DMA = N,N-dimethylacetamide) has been prepared employing the solvothermal method using L₁ and L₂ in DMA medium. Single crystal X-ray diffraction analysis revealed {[Cd(L₁)(L₂)](DMA)}_n is crystallized in orthorhombic system with space group Cmca. {[Cd(L₁)(L₂)](DMA)}_n features an interpenetrated 3D framework structure consist of pendant Lewis basic –NH₂ groups directed towards the pores. Thermogravimetric analysis revealed that the desolvated framework compound is stable up to 350 °C under nitrogen atmosphere. Furthermore, porosity of the desolvated {[Cd(L₁)(L₂)](DMA)}_n has been investigated through N₂, H₂ and CO₂ adsorption studies as well as sorption of water vapour. {[Cd(L₁)(L₂)](DMA)}_n exhibits superior selective turn on sensing towards tri-positive metal ions (Al³⁺, Fe³⁺, Cr³⁺) and luminescence quenching behavior towards nitroaromatics with high selectivity.