2 research outputs found
Mechanism and Kinetics for Reaction of the Chemical Warfare Agent Simulant, DMMP(<i>g</i>), with Zirconium(IV) MOFs: An Ultrahigh-Vacuum and DFT Study
The mechanism and
kinetics of interactions between dimethyl methylphosphonate
(DMMP), a key chemical warfare agent (CWA) simulant, and Zr<sub>6</sub>-based metal organic frameworks (MOFs) have been investigated with
in situ infrared spectroscopy (IR), X-ray photoelectron spectroscopy
(XPS), powder X-ray diffraction (PXRD), and DFT calculations. DMMP
was found to adsorb molecularly to UiO-66 through the formation of
hydrogen bonds between the phosphoryl oxygen and the free hydroxyl
groups associated with Zr<sub>6</sub> nodes on the surface of crystallites
and not within the bulk MOF structure. Unlike UiO-66, the infrared
spectra for UiO-67 and MOF-808, recorded during DMMP exposure, suggest
that uptake occurs through both physisorption and chemisorption. The
XPS spectra of MOF-808 zirconium 3d electrons reveal a charge redistribution
following exposure to DMMP. In addition, analysis of the phosphorus
2p electrons following exposure and thermal annealing to 600 K indicates
that two types of stable phosphorus-containing species exist within
the MOF. DFT calculations, used to guide the IR band assignments and
to help interpret the XPS features, suggest that uptake is driven
by nucleophilic addition of an OH group to DMMP with subsequent elimination
of a methoxy substituent to form strongly bound methyl methylphosphonic
acid (MMPA). The rates of product formation indicate that there are
likely two distinct uptake processes, requiring rate constants that
differ by approximately an order of magnitude. However, the rates
of molecular uptake were found to be nearly identical to the rates
of reaction, which strongly suggests that the reaction rates are diffusion-limited.
The final products were found to inhibit further reactions within
the MOFs, and these products could not be thermally driven from the
MOFs prior to decomposition of the MOFs themselves
sj-docx-1-jdr-10.1177_00220345231182052 – Supplemental material for Fibulin-1 Regulates Initiation of Successional Dental Lamina
Supplemental material, sj-docx-1-jdr-10.1177_00220345231182052 for Fibulin-1 Regulates Initiation of Successional Dental Lamina by G. Li, Q. Li, Z. Shen, X. Lin, X. Li, J. Wang, B. Zhao, Y. Feng, L. Feng, W. Guo, L. Hu, J. Wang, C. Zhang, Z. Fan, S. Wang and X. Wu in Journal of Dental Research</p