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Stability of Iodine Species Trapped in Titanium-Based MOFs: MIL-125 and MIL-125_NH 2
Two titanium-based MOFs MIL-125 and MIL-125_NH are synthesized and characterized using high-temperature powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), N sorption, Fourier transformed infrared spectroscopy (FTIR), Raman spectroscopy, ultraviolet-visible spectroscopy (UV-Vis), and...
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Published in: | Small (Weinheim an der Bergstrasse, Germany) Germany), 2024-08, Vol.20 (35), p.e2400265 |
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Main Authors: | , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites |
Online Access: | Get full text |
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Summary: | Two titanium-based MOFs MIL-125 and MIL-125_NH
are synthesized and characterized using high-temperature powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), N
sorption, Fourier transformed infrared spectroscopy (FTIR), Raman spectroscopy, ultraviolet-visible spectroscopy (UV-Vis), and electron paramagnetic resonance (EPR). Stable up to 300 °C, both compounds exhibited similar specific surface areas (SSA) values (1207 and 1099 m
g
for MIL-125 and MIL-125_NH
, respectively). EPR signals of Ti
are observed in both, whith MIL-125_NH
also showing ─NH
signatures. Both MOFs efficiently adsorbed iodine in continuous gas flow over five days, with MIL-125 trapping 1.9 g.g
and MIL-125_NH
trapping 1.6 g.g
. MIL-125_NH
exhibited faster adsorption kinetics due to its smaller band gap (2.5 against 3.6 eV). In situ Raman spectroscopy conducted during iodine adsorption revealed signal evolution from "free" I
to "perturbed" I
, and I
. TGA and in situ Raman desorption experiments showed that ─NH
groups improved the stabilization of I
due to an electrostatic interaction with NH
BDC radicals. The Albery model indicated longer lifetimes for iodine desorption in I
@MIL-125_NH
, attributed to a rate-limiting step due to stronger interaction between the anionic iodine species and the ─NH
radicals. This study underscores how MOFs with efficient charge separation and hole-stabilizer functional groups enhance iodine stability at higher temperatures. |
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ISSN: | 1613-6810 1613-6829 |
DOI: | 10.1002/smll.202400265 |