A new microporous Zr4+ MOF combines both extraordinary sorption capability and exceptional luminescence sensing properties for Cr(vi) in aqueous media.

In this review we approach the emerging field of sensors based on luminescent metal–organic frameworks from the perspective of the most commonly encountered pitfalls and we suggest best practices so that they can be avoided.

A Zr4+ MOF shows an exceptional capability to capture TcO4− and selective luminescence sensing for ReO4−, demonstrated for the first time for MOF materials.

Increasing global environmental pollution due to heavy metal ions raises the importance of research on new multifunctional materials for simultaneous detection and removal of these contaminants from water resources. In this study, we report a microporous 8-connected Zr4+ metal–organic framework (MOF) based on a terephthalate ligand decorated with a chelating 2-picolylamine side group (dMOR-2), which shows highly efficient fluorescence sensing and sorption of heavy metal cations. We demonstrate by detailed fluorescence studies the ability of a water-dispersible composite of dMOR-2 with polyvinylpyrrolidone for real-time detection of Cu2+, Pb2+, and Hg2+ in aqueous media. The limits of detection were found to be below 2 ppb for these species, while the system’s performance is not affected by the presence of other potentially competitive ions. In addition, sorption studies showed that a composite of dMOR-2 with calcium alginate (dMOR-2@CaA) is an excellent sorbent for Pb2+ and Cu2+ ions with capacities of 376 ± 15 and 117 ± 4 mg per gram of dMOR-2@CaA, respectively, while displaying the capability for simultaneous removal of various heavy metal ions in low initial concentrations and in the presence of large excesses of other cationic species. Structural and spectroscopic studies with model ligands analogous to our material’s receptor unit showed chelation to the 2-picolylamine moiety to be the main binding mode of metal ions to dMOR-2. Overall, dMOR-2 is shown to represent a rare example of a MOF, which combines sensitive fluorescence detection and high sorption capacity for heavy metal ions.

The amorphous compound [Mg(H2dhtp)(H2O)2] 1′ was shown to be a highly efficient and reusable luminescent sensor for the detection of water in THF, due to its transformation to the strongly emissive complex [Mg(H2dhtp)(H2O)5]·H2O 1.

Trivalent lanthanide ions (Ln 3+ ) hold an exceptional position in the field of optoelectronic materials due to their atomic-like emission spectra and long luminescence lifetimes. Metal−organic frameworks (MOFs) and coordination polymers are particularly suited as luminescent materials due to their structural diversity and ease of functionalization both at bridging ligands and/or metal centers. In this contribution, we present a series of mixed-metal Ln 3+ /Eu 3+ (Ln = La, Gd) and mixed-ligand (2,6-naphthalenedicarboxylate (ndc 2− ) and 4-aminonaphthalene-2,6-dicarboxylate (andc 2− )) MOFs belonging to three different structural types, with emissions spanning most of the visible region, thereby constituting favorable materials for color tuning and whitelight emission. We investigate the thermal stability and photophysical properties of the synthesized materials with regard to their metal and ligand doping levels and structural type, where we discuss excimer and monomer emission. The photophysical study, involving both steady-state and time-resolved luminescence measurements, allows us to discuss the possible energy migration and Eu 3+ sensitization pathways that take place within these materials following ligand excitation. Low-temperature luminescence studies led us to determine the energies of the ligand-based excited states and investigate their participation in thermally activated energy transfer mechanisms within the studied lattices. We observe emission quantum yields of up to 87% for the Eu 3+ -doped materials, while their ligand-and metal-doped counterparts show decreased quantum yields of up to 17%. Finally, we attempt fine color tuning by carefully adjusting the doping levels to achieve yellow and white-light emission.

In this study, we report the luminescence color tuning in the lanthanide metal-organic framework (LnMOF) ([La(bpdc)Cl(DMF)] (1); bpdc2− = [1,1′-biphenyl]-4,4′-dicarboxylate, DMF = N,N-dimethylformamide) by introducing dual emission properties in a La3+ MOF scaffold through doping with the blue fluorescent 2,2′-diamino-[1,1′-biphenyl]-4,4′-dicarboxylate (dabpdc2−) and the red emissive Eu3+. With a careful adjustment of the relative doping levels of the lanthanide ions and bridging ligands, the color of the luminescence was modulated, while at the same time the photophysical characteristics of the two chromophores were retained. In addition, the photophysical properties of the parent MOF (1) and its doped counterparts with various dabpdc2−/bpdc2− and Eu3+/La3+ ratios and the photoinduced energy transfer pathways that are possible within these materials are discussed. Finally, the temperature dependence study on the emission profile of a doped analogue containing 10% dabpdc2− and 2.5% Eu3+ (7) is presented, highlighting the potential of this family of materials to behave as temperature sensors.

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