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Mercury clathration-driven phase transition in a luminescent bipyrazolate metal-organic framework: a multitechnique investigation

Mercury clathration-driven phase transition in a luminescent bipyrazolate metal-organic framework: a multitechnique investigation

Authors :
Marco Moroni
Luca Nardo
Angelo Maspero
Guglielmo Vesco
Marco Lamperti
Luca Scapinello
Rebecca Vismara
Jorge A. R. Navarro
Damiano Monticelli
Andrea Penoni
Massimo Mella
Simona Galli
Publication Year :
2023

Abstract

Mercury is one of the most toxic heavy metals. By virtue of its triple bond, the novel ligand 1,2-bis(1H-pyrazol-4- yl)ethyne (H2BPE) was expressly designed and synthesized to devise metal−organic frameworks (MOFs) exhibiting high chemical affinity for mercury. Two MOFs, Zn(BPE) and Zn(BPE)·nDMF [interpenetrated i-Zn and noninterpenetrated ni-Zn·S, respectively; DMF = dimethylformamide], were isolated as microcrystalline powders. While i-Zn is stable in water for at least 15 days, its suspension in HgCl2 aqueous solutions prompts its conversion into HgCl2@ni-Zn. A multitechnique approach allowed us to shed light onto the observed HgCl2-triggered i-Zn-to- HgCl2@ni-Zn transformation at the molecular level. Density functional theory calculations on model systems suggested that HgCl2 interacts via the mercury atom with the carbon−carbon triple bond exclusively in ni-Zn. Powder X-ray diffraction enabled us to quantify the extent of the i-Zn-to-HgCl2@ni-Zn transition in 100−5000 ppm HgCl2 (aq) solutions, while X-ray fluorescence and inductively coupled plasma-mass spectrometry allowed us to demonstrate that HgCl2 is quantitatively sequestered from the aqueous phase. Irradiating at 365 nm, an intense fluorescence is observed at 470 nm for ni-Zn·S, which is partially quenched for i-Zn. This spectral benchmark was exploited to monitor in real time the i-Zn-to-HgCl2@ni-Zn conversion kinetics at different HgCl2 (aq) concentrations. A sizeable fluorescence increase was observed, within a 1 h time lapse, even at a concentration of 5 ppb. Overall, this comprehensive investigation unraveled an intriguing molecular mechanism, featuring the disaggregation of a water-stable MOF in the presence of HgCl2 and the self-assembly of a different crystalline phase around the pollutant, which is sequestered and simultaneously quantified by means of a luminescence change. Such a case study might open the way to new-conception strategies to achieve real-time sensing of mercury-containing pollutants in wastewaters and, eventually, pursue their straightforward and costeffective purification.<br />University of Insubria for partial funding<br />Programa Juan de la Cierva Formación (FJC2020-045043-I)<br />MCIN/AEI/10.13039/501100011033<br />European Union NextGenerationEU/PRTR (Grants PID2020- 113608RB-I00 and TED2021-129886B-C41)

Details

Language :
English
Database :
OpenAIRE
Accession number :
edsair.doi.dedup.....4f2cf6a32fb0e726f05e2f73aa077314