skip to main content


Title: A Metal‐Organic Framework (MOF)‐Based Multifunctional Cargo Vehicle for Reactive‐Gas Delivery and Catalysis
Abstract

The efficient delivery of reactive and toxic gaseous reagents to organic reactions was studied using metal‐organic frameworks (MOFs). The simultaneous cargo vehicle and catalytic capabilities of several MOFs were probed for the first time using the examples of aromatization, aminocarbonylation, and carbonylative Suzuki–Miyaura coupling reactions. These reactions highlight that MOFs can serve a dual role as a gas cargo vehicle and a catalyst, leading to product formation with yields similar to reactions employing pure gases. Furthermore, the MOFs can be recycled without sacrificing product yield, while simultaneously maintaining crystallinity. The reported findings were supported crystallographically and spectroscopically (e.g., diffuse reflectance infrared Fourier transform spectroscopy), foreshadowing a pathway for the development of multifunctional MOF‐based reagent‐catalyst cargo vessels for reactive gas reagents as an attractive alternative to the use of toxic pure gases or gas generators.

 
more » « less
Award ID(s):
1955768
NSF-PAR ID:
10368021
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Angewandte Chemie International Edition
Volume:
61
Issue:
12
ISSN:
1433-7851
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    The efficient delivery of reactive and toxic gaseous reagents to organic reactions was studied using metal‐organic frameworks (MOFs). The simultaneous cargo vehicle and catalytic capabilities of several MOFs were probed for the first time using the examples of aromatization, aminocarbonylation, and carbonylative Suzuki–Miyaura coupling reactions. These reactions highlight that MOFs can serve a dual role as a gas cargo vehicle and a catalyst, leading to product formation with yields similar to reactions employing pure gases. Furthermore, the MOFs can be recycled without sacrificing product yield, while simultaneously maintaining crystallinity. The reported findings were supported crystallographically and spectroscopically (e.g., diffuse reflectance infrared Fourier transform spectroscopy), foreshadowing a pathway for the development of multifunctional MOF‐based reagent‐catalyst cargo vessels for reactive gas reagents as an attractive alternative to the use of toxic pure gases or gas generators.

     
    more » « less
  2. Abstract

    Ammonia is a widely used toxic industrial chemical that can cause severe respiratory ailments. Therefore, understanding and developing materials for its efficient capture and controlled release is necessary. One such class of materials is 3D porous metal‐organic frameworks (MOFs) with exceptional surface areas and robust structures, ideal for gas storage/transport applications. Herein, interactions between ammonia and UiO‐67‐X (X: H, NH2, CH3) zirconium MOFs were studied under cryogenic, ultrahigh vacuum (UHV) conditions using temperature‐programmed desorption mass spectrometry (TPD‐MS) and in‐situ temperature‐programmed infrared (TP‐IR) spectroscopy. Ammonia was observed to interact with μ3−OH groups present on the secondary building unit of UiO‐67‐X MOFs via hydrogen bonding. TP‐IR studies revealed that under cryogenic UHV conditions, UiO‐67‐X MOFs are stable towards ammonia sorption. Interestingly, an increase in the intensity of the C−H stretching mode of the MOF linkers was detected upon ammonia exposure, attributed to NH−π interactions with linkers. These same binding interactions were observed in grand canonical Monte Carlo simulations. Based on TPD‐MS, binding strength of ammonia to three MOFs was determined to be approximately 60 kJ mol−1, suggesting physisorption of ammonia to UiO‐67‐X. In addition, missing linker defect sites, consisting of H2O coordinated to Zr4+sites, were detected through the formation ofnNH3⋅H2O clusters, characterized through in‐situ IR spectroscopy. Structures consistent with these assignments were identified through density functional theory calculations. Tracking these bands through adsorption on thermally activated MOFs gave insight into the dehydroxylation process of UiO‐67 MOFs. This highlights an advantage of using NH3for the structural analysis of MOFs and developing an understanding of interactions between ammonia and UiO‐67‐X zirconium MOFs, while also providing directions for the development of stable materials for efficient toxic gas sorption.

     
    more » « less
  3. Abstract. We present a novel photolytic source of gas-phase NO3 suitable for use in atmospheric chemistry studies that has several advantages over traditional sources that utilize NO2 + O3 reactions and/or thermal dissociation of dinitrogen pentoxide (N2O5). The method generates NO3 via irradiation of aerated aqueous solutions of ceric ammonium nitrate (CAN, (NH4)2Ce(NO3)6) and nitric acid (HNO3) or sodium nitrate (NaNO3). We present experimental and model characterization of the NO3 formation potential of irradiated CAN / HNO3 and CAN / NaNO3 mixtures containing [CAN] = 10−3 to 1.0 M, [HNO3] = 1.0 to 6.0 M, [NaNO3] = 1.0 to 4.8 M, photon fluxes (I) ranging from 6.9 × 1014 to 1.0 × 1016 photons cm−2 s−1, and irradiation wavelengths ranging from 254 to 421 nm. NO3 mixing ratios ranging from parts per billion to parts per million by volume were achieved using this method. At the CAN solubility limit, maximum [NO3] was achieved using [HNO3] ≈ 3.0 to 6.0 M and UVA radiation (λmax⁡ = 369 nm) in CAN / HNO3 mixtures or [NaNO3] ≥ 1.0 M and UVC radiation (λmax⁡ = 254 nm) in CAN / NaNO3 mixtures. Other reactive nitrogen (NO2, N2O4, N2O5, N2O6, HNO2, HNO3, HNO4) and reactive oxygen (HO2, H2O2) species obtained from the irradiation of ceric nitrate mixtures were measured using a NOx analyzer and an iodide-adduct high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS). To assess the applicability of the method for studies of NO3-initiated oxidative aging processes, we generated and measured the chemical composition of oxygenated volatile organic compounds (OVOCs) and secondary organic aerosol (SOA) from the β-pinene + NO3 reaction using a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to the HR-ToF-CIMS.

     
    more » « less
  4. null (Ed.)
    Defense against small molecule toxic gases is an important aspect of protection against chemical and biological threat as well as chemical releases from industrial accidents. Current protective respirators/garments cannot effectively block small molecule toxic gases and vapors and retain moisture transmission capability without a heavy burden. Here, we developed a nanopacked bed of nanoparticles of UiO-66-NH₂ metal organic framework (MOF) by synthesizing them in the pores of microporous expanded polytetrafluoroethylene (ePTFE) membranes. The submicron scale size of membrane pores ensures a large surface area of MOF nanoparticles which can capture/adsorb and react with toxic gas molecules efficiently. It was demonstrated that the microporous ePTFE membrane with UiO-66-NH₂ MOF grown inside and around the membrane can defend against ammonia for a significant length of time while allowing passage of moisture and nitrogen. It was also demonstrated that the MOF-loaded ePTFE membrane could provide significant protection from Cl₂ intrusion as well as intrusion from 2-chloroethyl ethyl sulfide (CEES) (a simulant for sulfur mustard). Such MOF-filled membranes exhausted by NH₃ breakthrough experiments were regenerated conveniently by heating at 60 °C for one week under vacuum for further/repeated use; a single regenerated membrane could block NH₃ for 200–300 min. The moisture permeability of such a membrane/nanopacked bed was considerably above the breathability threshold value of 2000 g/m² -day. The results suggest that microporous membranes filled with reactive MOF nanoparticles could be designed as protective barriers against toxic gases/vapors, e.g., NH₃ and Cl₂ and yet be substantially permeable to H₂O and air. 
    more » « less
  5. Context. Formaldehyde is a potential biogenic precursor involved in prebiotic chemical evolution. The cold conditions of the interstellar medium (ISM) allow H 2 CO to be reactive, playing a significant role as a chemical intermediate in formation pathways leading to interstellar complex organic molecules. However, gas-phase molecular formation mechanisms in cold regions of the ISM are poorly understood. Aims. We computationally determine the most favored gas-phase molecular formation mechanisms at local thermodynamic equilibrium conditions that can produce the detected amounts of H 2 CO in diffuse molecular clouds (DMCs), in dark, cold, and dense molecular clouds (DCDMCs), and in three regions of circumstellar envelopes of low-mass protostars (CELMPs). Methods. The potential energy surfaces, thermodynamic functions, and single-point energies for transition states were calculated at the CCSD(T)-F12/cc-pVTZ-F12 and MP2/aug-cc-pVDZ levels of theory and basis sets. Molecular thermodynamics and related partition functions were obtained by applying the Maxwell-Boltzmann quantum statistics theory from energies computed at CCSD(T)-F12/cc-pVTZ-F12 with corrections for zero-point energy. A literature review on detected abundances of reactants helped us to propose the most favorable formation routes. Results. The most probable reactions that produce H 2 CO in cold astrophysical regions are: 1 CH 2 + ⋅ 3 O 2 → 1 H 2 CO + O⋅( 3 P) in DMCs, ⋅ 3 CH 2 + ⋅ 3 O 2 → 1 H 2 CO + ⋅O( 3 P) in DCDMCs, and ⋅CH 3 + ⋅O( 3 P) → 1 H 2 CO + ⋅H in region III, ⋅CH 3 +⋅O( 1 D) → 1 H 2 CO + ⋅H in region II, and 1 CH 2 + ⋅ 3 O 2 → 1 H 2 CO + ⋅O( 3 P) in region I belonging to CELMPs. Conclusions. Quantum chemical calculations suggest that the principal carbonaceous precursors of H 2 CO in cold regions for the gas-phase are CH 2 (a 1 A 1 ), and ⋅CH 2 (X 3 B 1 ) combined with ⋅O 2 ( 3 Σ g ) and ⋅CH 3 ( 2 A ” ) + ⋅O( 3 P) / O( 1 D). Reactions based on more complex reagents yield less effective thermodynamics in the gas-phase H 2 CO molecular formation. 
    more » « less