Defect Level and Particle Size Effects on the Hydrolysis of a Chemical Warfare Agent Simulant by UiO-66

Abstract

Defect engineering in metal−organic frameworks (MOFs) has recently become an area of significant research due to the possibility of enhancing material properties such as internal surface area and catalytic activity while maintaining stable 3D structures. Through a modulator screening study, the model Zr 4+ MOF, UiO-66, has been synthesized with control of particle sizes (100−1900 nm) and defect levels (2−24%). By relating these properties, two series were identified where one property remained constant, allowing for independent analysis of the defect level or particle size, which frequently change coincident with the modulator choice. The series were used to compare UiO-66 reactivity for the hydrolysis of a chemical warfare agent simulant, dimethyl 4-nitrophenylphosphate (DMNP). The rate of DMNP hydrolysis displayed high dependence on the external surface area, supporting a reaction dominated by surface interactions. Moderate to high concentrations of defects (14−24%) allow for the accessibility of some interior MOF nodes but do not substantially promote diffusion into the framework. Individual control of defect levels and particle sizes through modulator selection may provide useful materials for small molecular catalysis and provide a roadmap for similar engineering of other zirconium frameworks.

Aggregation-Suppressed Porous Processable Hexa-Zirconium/Polymer Composites for Detoxification of a Nerve Agent Simulant

“…Since DMNP hydrolysis is known to be surface limited in microporous systems, it is reasonable for the smaller particle size powder composites to hydrolyze at a faster rate due to the more exposed active sites on the surface. 43 To evaluate the strength of the physical encapsulation, we collected the composites post hydrolysis and washed them with water to remove any residual organophosphate species from the hydrolysis. The Zr loading was again determined by ICP-OES to compare the amount of Zr 6 clusters in the composites before and after hydrolysis.…”

Vibrational spectroscopy investigation of defects in Zr- and Hf-UiO-66

“…Defective UiO-66 samples containing missing linkers were synthesized following previously reported procedures. 20 Briefly, 378.1 mg ZrCl 4 and 539 mg of terephthalic acid were added to 10 mL of dimethylformamide (DMF) in a 6 dr glass vial. Modulator was added (6.3 mL acetic acid, 2.8 mL formic acid, or 4.2 mL formic acid) to produce defective Zr-UiO-66 with 14%, 22%, and 25% missing linkers respectively.…”

“…Missing linker defects were characterized by thermogravimetric analysis (TGA) on a TA TGA-5500 under an air flow from 30–650 °C with a 10 °C min −1 ramp rate as per ref. 20 . N 2 isotherms were collected on a Micromeritics 3Flex at 77 K. The samples were activated at 150 °C under vacuum overnight to remove excess moisture prior to analysis.…”

Pore-confined cobalt sulphide nanoparticles in a metal–organic framework as a catalyst for the colorimetric detection of hydrogen peroxide

“…18,26,28,29 Therefore, incorporating catalytically active species into the water-stable and highly porous Zr-MOFs has been considered as an appealing strategy to design the heterogeneous catalysts utilized in aqueous environments. [30][31][32][33] Transition metal sulphides have garnered great attention as heterogeneous catalysts among various materials. 34 However, the in-situ synthesis of metal sulphides within the nanopore of MOFs is relatively challenging because most MOFs cannot preserve their structural integrity in the environments containing S 2ions, HSions, or H 2 S vapor.…”

“…18,26,28,29 Therefore, incorporating catalytically active species into water-stable and highly porous Zr-MOFs has been considered as an appealing strategy to design the heterogeneous catalysts utilized in aqueous environments. 30–33…”