Constructing functional metal-organic frameworks by ligand design for environmental applications

Metal-organic frameworks (MOFs) with unique physical and chemical properties are composed of metal ions/clusters and organic ligands, including high porosity, large specific surface area, tunable structure and functionality, which have been widely used in chemical sensing, environmental remediation, and other fields. Organic ligands have a significant impact on the performance of MOFs. Selecting appropriate types, quantities and properties of ligands can well improve the overall performance of MOFs, which is one of the critical issues in the synthesis of MOFs. This article provides a comprehensive review of ligand design strategies for functional MOFs from the number of different types of organic ligands. Single-, dual- and multi-ligand design strategies are systematically presented. The latest advances of these functional MOFs in environmental applications, including pollutant sensing, pollutant separation, and pollutant degradation are further expounded. Furthermore, an outlook section of providing some insights on the future research problems and prospects of functional MOFs is highlighted with the purpose of conquering current restrictions by exploring more innovative approaches.

Two porous three-dimensional (3D) metal–organic frameworks based on diverse metal clusters: selective sensing of Fe3+ and Cr2O72−

Using a rigid 3,5-di(2′,5′-dicarboxylphenyl)benzoic acid, two porous 3D MOFs have been synthesized and characterized, and the luminescent properties have been studied.

Water-assisted proton conductivity of two highly stable imidazole multi-carboxylate-based MOFs

The proton conduction and proton mechanisms of two highly stable imidazole multi-carboxylate-based MOFs have been investigated and discussed.

Two dimethylphenyl imidazole dicarboxylate-based lanthanide metal–organic frameworks for luminescence sensing of benzaldehyde

Two novel dimethylphenyl imidazole dicarboxylate-based lanthanide(iii)-organic frameworks, [Ln(H₂DMPhIDC)₃(H₃DMPhIDC)]_n (Ln = Eu (1), Tb (2); H₃DMPhIDC = 2-(3,4-dimethylphenyl)-1H-imidazole-4,5-dicarboxylic acid) have been synthesized under hydrothermal conditions.

Selective pyridine recognition by an imidazole dicarboxylate-based 3D cadmium(ii) MOF

One newly prepared 3D polymer (1) composed of left- and right-handed helices containing [Cd₈(p-ClPhHIDC)₁₂(4,4′-bipy)₆] cages shows selective pyridine recognition, with a visual colour change from pearl to pink under ultraviolet irradiation.

Five metal–organic frameworks from 3,4-dimethylphenyl substituted imidazole dicarboxylate: syntheses, structures and properties

Five metal–organic frameworks have been hydrothermally synthesized and structurally characterized.

Anion-dependent assemblies of a series of Cd(ii) coordination complexes based on an asymmetric multi-dentate ligand and inorganic SBUs: syntheses, crystal structures, and fluorescent properties

Six novel Cd(ii) complexes based 1-(benzotriazole-1-methyl)-2- propylimidazole are synthesized. These complexes share common features such as they all contain inorganic SBUs and have a high degree of dependence on the corresponding counter anions.

Syntheses, crystal structures and thermal properties of six coordination polymers based on 2-(p-methylphenyl)-imidazole dicarboxylate

Through solvothermal reactions of 2-(p-methylphenyl)-1H-imidazole-4,5-dicarboxylic acid (p-MePhH3IDC) with transition-metal ions, six coordination polymers [Pb2(p-MePhHIDC)(p-MePhH2IDC)2(phen)2]n (phen = 1,10-phenanthroline) (), [Pb(p-MePhH2IDC)2]n (), [Cd3(p-MePhHIDC)2(p-MePhH2IDC)2(H2O)2]n (), {[Cd(p-MePhHIDC)(H2O)]4·H2O}n (), {[Cd2(p-MePhHIDC)2(4,4'-bipy)]·4H2O}n (4,4'-bipy = 4,4'-bipyridine) () and [Mn3(p-MePhHIDC)2(p-MePhH2IDC)2(4,4'-bipy)]n () have been synthesized successfully. X-ray single-crystal analyses show that polymers have rich structural chemistry ranging from one-dimensional (), two-dimensional () to three-dimensional polymers (, , and ). In these polymers, the p-MePhH3IDC ligand shows flexible coordination modes tuned by different synthetical conditions, including the addition of coligands, temperature, pH value and so on. Furthermore, the polymers have been investigated by solid-state ultraviolet spectra and thermogravimetric analyses.