Upon liquid phase adsorption of C-C primary alcohols on high silica MFI zeolites (Si/Al = 11.5-140), the concentration of adsorbed molecules largely exceeds the concentration of traditional adsorption sites: Brønsted acid and defect sites. Combining quantitative H MAS NMR, qualitative multinuclear NMR and IR spectroscopy, hydrogen bonding of the alcohol function to oxygen atoms of the zeolite siloxane bridges (Si-O-Si) was shown to drive the additional adsorption.
View Article and Find Full Text PDFSolid-state nuclear magnetic resonance can be enhanced using unpaired electron spins with a method known as dynamic nuclear polarization (DNP). Fundamentally, DNP involves ensembles of thousands of spins, a scale that is difficult to match computationally. This scale prevents us from gaining a complete understanding of the spin dynamics and applying simulations to design sample formulations.
View Article and Find Full Text PDFApplying metal-organic frameworks (MOFs) on the surface of other materials to form multifunctional materials has recently attracted great attention; however, directing the MOF overgrowth is challenging due to the orders of magnitude differences in structural dimensions. In this work, we developed a universal strategy to mediate MOF growth on the surface of metal nanoparticles (NPs), by taking advantage of the dynamic nature of weakly adsorbed capping agents. During this colloidal process, the capping agents gradually dissociate from the metal surface, replaced by the MOF.
View Article and Find Full Text PDFFour-carbon olefins, such as 1-butene and 1,3-butadiene, are important chemical feedstocks for the production of adhesives and synthetic rubber. These compounds are found in the C fraction of "green oil" products that can arise during the hydrogenation of acetylene. Here, we demonstrate that control of the catalyst structure increases the yield and productivity of these important olefins with a family of catalyst materials comprising Cu nanoparticles (CuNPs) bound within the pores of Zr-based metal-organic frameworks.
View Article and Find Full Text PDFHere we design an interface between a metal nanoparticle (NP) and a metal-organic framework (MOF) to activate an inert CO carboxylation reaction and in situ monitor its unconventional regioselectivity at the molecular level. Using a Kolbe-Schmitt reaction as model, our strategy exploits the NP@MOF interface to create a pseudo high-pressure CO microenvironment over the phenolic substrate to drive its direct C-H carboxylation at ambient conditions. Conversely, Kolbe-Schmitt reactions usually demand high reaction temperature (>125 °C) and pressure (>80 atm).
View Article and Find Full Text PDFDNAzymes are a promising class of bioinspired catalyst; however, their structural instability limits their potential. Herein, a method to stabilize DNAzymes by encapsulating them in a metal-organic framework (MOF) host is reported. This biomimetic mineralization process makes DNAzymes active under a wider range of conditions.
View Article and Find Full Text PDFWe investigated lattice strain on alloyed surfaces using ∼10 nm core-shell nanoparticles with controlled size, shape, and composition. We developed a wet-chemistry method for synthesizing small octahedral PdPt alloy nanoparticles and Au@PdPt core-shell nanoparticles with Pd-Pt alloy shells and Au cores. Upon introduction of the Au core, the size and shape of the overall nanostructure and the composition of the alloyed PdPt were maintained, enabling the use of the electrooxidation of formic acid as a probe to compare the surface structures with different lattice strain.
View Article and Find Full Text PDFControlling the surface composition of shaped bimetallic nanoparticles could offer precise tunability of geometric and electronic surface structure for new nanocatalysts. To achieve this goal, a platform for studying the intermixing process in a shaped nanoparticle was designed, using multilayered Pd-Ni-Pt core-shell nanocubes as precursors. Under mild conditions, the intermixing between Ni and Pt could be tuned by changing layer thickness and number, triggering intermixing while preserving nanoparticle shape.
View Article and Find Full Text PDFWe studied coordination-dependent surfactant binding on shaped MOF nanocrystals. Cetyltrimethylammonium bromide (CTAB) on the surface of ZIF-8 was used as a model system. Infrared spectroscopic analysis and molecular dynamics simulations reveal different coordination environments for Zn nodes on {100} and {110} facets, resulting in different CTAB adsorption.
View Article and Find Full Text PDFAn oxidative linker cleaving (OLC) process was developed for surgical manipulation of the engraving process within single crystalline MOFs particles. The strategy relies on selective degradation of 2,5-dihydroxyterephthalic acid linker into small molecular fragments by oxidative ring-opening reactions, resulting in controllable scissoring of framework. By regulation of the generation and diffusion of oxidative species, the core MOFs will undergo divergent etching routes, producing a series of single crystalline hollow and yolk-shell MOF structures.
View Article and Find Full Text PDFMetal-organic frameworks (MOFs) have recently garnered consideration as an attractive solid substrate because the highly tunable MOF framework can not only serve as an inert host but also enhance the selectivity, stability, and/or activity of the enzymes. Herein, we demonstrate the advantages of using a mechanochemical strategy to encapsulate enzymes into robust MOFs. A range of enzymes, namely β-glucosidase, invertase, β-galactosidase, and catalase, are encapsulated in ZIF-8, UiO-66-NH, or Zn-MOF-74 via a ball milling process.
View Article and Find Full Text PDFACS Appl Mater Interfaces
October 2019
Metal-organic frameworks (MOFs) is a promising class of sorbent materials for swing adsorption gas separation. However, although sorption kinetics plays a major role in column breakthrough experiments, it is rarely studied with MOF materials. This is largely because the synthesis of uniform yet separation-relevant MOFs is a challenging task.
View Article and Find Full Text PDFThe incompatibility between the anode and the cathode chemistry limits the used of Mg as an anode. This issue may be addressed by separating the anolyte and the catholyte with a membrane that only allows for Mg transport. Mg-MOF-74 thin films were used as the separator for this purpose.
View Article and Find Full Text PDFA UiO-66 analog was synthesized in 100 s using water-assisted grinding. The linker solubility suggested that tetrafluorobenzene-1,4-dicarboxylic acid was the best linker. Zr-metal-organic framework nanocrystals displayed good topologies and hydrophobicities, and high water/thermal stabilities.
View Article and Find Full Text PDFWe show that an enzyme maintains its biological function under a wider range of conditions after being embedded in metal-organic framework (MOF) microcrystals via a de novo approach. This enhanced stability arises from confinement of the enzyme molecules in the mesoporous cavities in the MOFs, which reduces the structural mobility of enzyme molecules. We embedded catalase (CAT) into zeolitic imidazolate frameworks (ZIF-90 and ZIF-8), and then exposed both embedded CAT and free CAT to a denature reagent (i.
View Article and Find Full Text PDFLong-range olefin isomerization of 2-alkenylbenzoic acid derivatives going through two to five sp-carbon atoms to give ()-alkenes was achieved with palladium(0) nanoparticles. The substrate scope of this reaction includes carboxylic acid, ester, and primary to tertiary amides and tolerates various substituents on the benzene ring. This isomerization reaction was catalyzed by recyclable Pd(0) nanoparticles, prepared in situ from PdCl and characterized by X-ray powder diffraction and scanning electron microscopy analyses.
View Article and Find Full Text PDFUsing a simple method, the aldehyde groups of zeolitic imidazolate framework-90 (ZIF-90) nanocrystals were converted into carboxyl, amino, and thiol groups, without affecting the integrity of the framework. Notably, for the first time, correlations between functionality and cytotoxicity are also demonstrated via in vitro cytotoxicity assays. The positive charged aminated-ZIF-90 presumably results in either perturbation of cell membrane, more efficient cell uptake, or both.
View Article and Find Full Text PDFDrug Metab Pharmacokinet
January 2014
The cytochrome P450 (P450, CYP) 2A6 inhibitor chalepensin was found to inhibit human CYP1A1, CYP1A2, CYP2A13, CYP2C9, CYP2D6, CYP2E1, and CYP3A4 to different extents. CYP1A1 and CYP3A4 underwent pronounced mechanism-based inactivation by chalepensin and had the smallest IC50 ratios of inhibition with NADPH-fortified pre-incubation (IC50(+)) to that without pre-incubation (IC50(-)). CYP2E1 had the least susceptibility to mechanism-based inactivation.
View Article and Find Full Text PDF