Metal-organic frameworks (MOFs) have applications ranging from gas storage and separation to catalysis and sensing. The materials can be tailored to specific uses by varying the contained metal atoms or ions and the organic ligands that hold them together. Luminescent MOFs, for example, can be used as fluorescent sensors.

Wei-Yin Sun, Nanjing University, China, and colleagues have synthesized and characterized four new MOFs, two of which could be useful for selectively sensing Fe(III) ions and ketones. The materials use a combination of carboxylate and nitrogen donor ligands. The team prepared [Zn(L)(bpdc)]·1.6 H₂O, [Co(L)(bpdc)]·H₂O, [Ni₃(L)₂(bptc)₂(H₂O)₁₀]·2 H₂O, and [Cd₂(L)(Hbptc)₂] (L = 1,4-di(1H-imidazol-4-yl)benzene, H₂bpdc = 4,4’-benzophenonedicaboxylic acid, H₃bptc = biphenyl-2,4′,5-tricarboxylic acid). The MOFs were synthesized by heating a mixture of the respective ligands with metal nitrates to 120°C in aqueous solution.

The researchers found that the zinc- and cadmium-based MOFs form 3D networks, while the nickel compound has a 2D structure, and the MOF containing cobalt forms 1D chains. Photoluminescence studies demonstrated that both the zinc- and cadmium-based MOFs show selective fluorescence quenching in the presence of either Fe(III) ions or ketones. According to the team, this effect makes these compounds potential sensing materials.

• Metal-organic frameworks with 1,4-di(1H-imidazol-4-yl)benzene and varied carboxylate ligands for selectively sensing Fe(III) Ion and ketone molecules,
  Zhi-Qiang Liu, Yue Zhao, Xiu-Du Zhang, Yan-Shang Kang, Qingyi Lu, Mohammad Azam, Saud I Al-Resayes, Wei-Yin Sun,
  Dalton Trans. 2017.
  DOI: 10.1039/c7dt02981k