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.
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