Synergy of Paired Brønsted-Lewis Acid Sites on Defects of Zr-MIL-140A for Methanol Dehydration.

As a common defect-capping ligand in metal-organic frameworks (MOFs), the hydroxyl group normally exhibits Brønsted acidity or basicity, but the presence of inherent hydroxyl groups in the MOF structure makes it a great challenge to identify the exact role of defect-capping hydroxyl groups in catalysis. Herein, we used hydroxyl-free MIL-140A as the platform to generate terminal hydroxyl groups on defect sites a continuous post-synthetic treatment. The structure and acidity of MIL-140A were properly characterized.

Fabricating defect-rich metal-organic frameworks mixed linker-induced crystal transformation.

Defect-rich hcp UiO-66-NO was synthesized mixed linker-induced crystal transformation from fcu UiO-66-NO/NH. The defect concentration and porosity of hcp UiO-66-NO can be fine-tuned by varying the BDC-NH/BDC-NO ratio, which in turn endowed hcp UiO-66-NO with superior catalytic performance in the ring-opening reaction of epoxides with alcohols.

Macro-composition quantification combined with metabolomics analysis uncovered key dynamic chemical changes of aging white tea.

It is a common belief in China that aging could improve the quality of white tea. However, the stored-induced compositional changes remain elusive. In this study, ten subsets of white tea samples, which had been stored for 1-, 2-, 3-, 4-, 5-, 6-, 7-, 10-, 11- and 13- years, were selected.

Pair Sites on Nodes of Metal-Organic Framework hcp UiO-66 Catalyze -Butyl Alcohol Dehydration.

On metal oxide cluster nodes of metal-organic frameworks (MOFs), sites not bonded to linkers (e.g., defects and structural vacancies) control reactivity and catalysis.

Computational Mechanistic Study of Brønsted Acid-Catalyzed Unsymmetrical 1,2,4,5-Tetrazines Synthesis.

Density functional theory (DFT) calculations were conducted to gain insight into the reaction mechanism of the Brønsted acid-catalyzed unsymmetrical 1,2,4,5-tetrazine synthesis. Various possible reaction pathways were considered, and the most favorable one can be characterized via sequential six steps, including addition of DCM to hydrazine giving complex , N-H bond activation in mediated by sulfur, AcOH-assisted substitution of with sulfur-activated hydrazine , HNO-assisted addition of nitrile to intermediate , cyclization, and intramolecular elimination leading to the final product . Among the six steps, sulfur activation of N-H bond is found to be the rate-determining step (RDS).

Mechanistic Study of the -Quaternized Pyridoxal-Catalyzed Biomimetic Asymmetric Mannich Reaction: Insights into the Origins of Enantioselectivity and Diastereoselectivity.

Density functional theory calculations have been performed to gain insights into the catalytic mechanism of the -quaternized pyridoxal (i.e., )-mediated biomimetic asymmetric Mannich reaction of -butyl glycinate with -diphenylphosphinyl imine to give the diamino acid ester in high yield with excellent enantiomeric and diastereomeric selectivity ( , , 1438).

Mechanistic study of the cooperative palladium/Lewis acid-catalyzed transfer hydrocyanation reaction: the origin of the regioselectivity.

Density functional theory (DFT) calculations have been performed to gain insights into the catalytic mechanism of the palladium/Lewis acid-catalyzed transfer hydrocyanation of terminal alkenes to reach the linear alkyl nitrile with excellent anti-Markovnikov selectivity. The study reveals that the whole catalysis can be characterized via three stages: (i) oxidative addition generates the π-allyl complex IM2, followed by β-hydride elimination leading to the intermediate IM4, (ii) ligand exchange followed by Pd-H migratory alkene insertion gives the anti-Markovnikov intermediate IM6 and (iii) IM6 undergoes a reductive elimination step to form the linear terminal nitrile 3a and regenerates the active species for the next catalytic cycle. Each stage is kinetically and thermodynamically feasible.

Correction to "Monitoring the Hierarchical Evolution from a Double-Stranded Helix to a Well-Defined Microscopic Morphology Based on a Turbine-like Aromatic Molecule".

[This corrects the article DOI: 10.1021/acsomega.0c01443.

Preparation of graphene oxide-modified palygorskite nanocomposites for high-efficient removal of Co(II) from wastewater.

Removing Co(II) from wastewater is urgent due to the threat to the environment and human health. In the work, the nanocomposite of graphene oxide-modified palygorskite (mPal-GO) is synthesized by cross-linking one-dimensional palygorskite (Pal) with two-dimensional material graphene oxide (GO), and used to remove Co(II) from wastewater. Its structure is characterized by Fourier transformed infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area measurement.

Monitoring the Hierarchical Evolution from a Double-Stranded Helix to a Well-Defined Microscopic Morphology Based on a Turbine-like Aromatic Molecule.

1-Indazolo[1,2-]phthalazine-5,10-dione IPDD with an approximate turbine-like spatial structure, primary assembled double-stranded helices at the first level, was predicted by quantum chemical calculations and confirmed by atomic force microscopy. The higher-dimensional hierarchical architectures including fibrils, helical fibers, spherical shells, and porous prismatic structures were observed in sequence by the scanning electron microscopy technique. The final porous prismatic structures sensitive to NH vapors have the potential to be applied in gas sensing and absorbing materials.

Complex emulsions for shape control based on mass transfer and phase separation.

Complex emulsions are used to fabricate new morphologies of multiple Janus droplets, evolving from non-engulfing to complete engulfing core/shell configuration. The produced droplets contain an aqueous phase of dextran (DEX) solution and an oil phase, which is mixed with ethoxylated trimethylolpropane triacrylate (ETPTA) and poly(ethylene glycol) diacrylate (PEGDA). The PEGDA in the oil phase is transferred into the aqueous phase to form complex morphologies due to the phase separation of PEGDA and DEX.

Preparation of Silica@Silica Core-Shell Microspheres Using an Aqueous Two-Phase System in a Novel Microchannel Device.

In the present work, a novel microchannel device was developed and used for the preparation of core-shell microspheres combining with a dextran/poly(ethylene glycol) diacrylate (DEX/PEGDA) aqueous two-phase system. Silica@silica core-shell microspheres were prepared as a model material. Silica@silica core-shell microspheres with different sizes of cores and thicknesses of shells were prepared by using different flowrate ratios of DEX/silica and PEGDA/silica aqueous solutions.

Shape-Anisotropic Diblock Copolymer Particles with Varied Internal Structures.

Anisotropic polymer particles have promising applications in various fields, whereas their preparation usually suffers from tedious procedures. Here, we introduce a facile strategy to fabricate novel shape-anisotropic particles with varied internal structures via self-assembly of block copolymers (BCPs), with perfluorooctane (PFO) as the liquid template in emulsion droplets. By increasing the volume ratio of PFO to polystyrene- block-poly(4-vinylpyridine) (PS- b-P4VP) or decreasing the initial concentration of the BCPs, the self-assembled polymer particles change from spherical core-shell structures to anisotropic particles.

Kinetically Controlled Self-Assembly of Block Copolymers into Segmented Wormlike Micelles in Microfluidic Chips.

Kinetically controlled self-assembly of block copolymers (BCPs) in solution is an efficient route to fabricate complex hierarchical colloids which are of great importance for nanoencapsulation, microreactors, and biomimics. Herein, segmented wormlike micelles (SWMs) with controllable size are generated by the self-assembly of polystyrene- block-poly(4-vinyl pyridine) in microfluidic channel. Different from the assembly of BCPs off-chip at the same solution properties, it is found that the fabricated SWMs are kinetically controlled assemblies with thermodynamic metastable structures, which are formed by the orderly aggregation of preformed spherical micelles because of the fast mixing process in microfluidic channels.

Regulating Block Copolymer Assembly Structures in Emulsion Droplets through Metal Ion Coordination.

In this report, we demonstrate the metal ion coordination-induced morphological transition of block copolymer assemblies under three-dimensional (3D) confinement. Polystyrene- block-poly(4-vinyl pyridine) (PS- b-P4VP) aggregates with various morphologies can be obtained by emulsion-solvent evaporation in the presence of metal ions (e.g.

Fabrication of PAA-PETPTA Janus Microspheres with Respiratory Function for Controlled Release of Guests with Different Sizes.

Poly(acrylic acid)-poly(ethoxylated trimethylolpropane triacrylate) (PAA-PETPTA) Janus microspheres with "respiratory" function for controlled release were prepared by polymerization of acrylic acid-ethoxylated trimethylolpropane triacrylate (AA-ETPTA) Janus microdroplets in a continuous oil phase in a simple capillary-based microfluidic device with the assistance of UV radiation. The flow rate ratios of AA and ETPTA phases and surfactant content in the continuous oil phase have a significant effect on the structure of the Janus microspheres. PAA part in the Janus microspheres has respiratory function for loading and release due to the different stimuli responses to different pHs.

Shaping metal-organic framework materials with a honeycomb internal structure.

A self-assembly technology allows metal-organic framework materials to constitute a honeycomb internal structure while being shaped into millimeter-scale spheres. The ZIF-8 load is up to 83 wt% through solidification of chitosan (CS). This approach can be expanded to other morphologies (fibers) or crystals and is transformative for industrial manufacturing of nanomaterials.

Two-Phase Diffusion Technique for the Preparation of Ultramacroporous/Mesoporous Silica Microspheres via Interface Hydrolysis, Diffusion, and Gelation of TEOS.

Honeycombed hierarchical ultramacroporous/mesoporous silica microspheres were prepared via the hydrolysis of TEOS in the oil-water interface, with subsequent diffusion and gelation in the acidic water-phase microdroplets with the assistance of a simple homemade microdevice. The diffusion of furfuryl alcohol (FA) also happened at a relatively high rate during the hydrolysis and diffusion of TEOS. Therefore, plenty of FA will be inside of the water microdroplets and form a decent number of polyfurfuryl alcohol (PFA) microparticles, thereby obtaining honeycombed hierarchical porosity silica microspheres with abundant ultramacroporous cavities and mesopores after calcination.

Complex Emulsions by Extracting Water from Homogeneous Solutions Comprised of Aqueous Three-Phase Systems.

Multiple emulsions can be obtained by binary and ternary liquid phase separation. And the use of the aqueous two-phase system provides a simple route to prepare water-in-water-in-oil (W/W/O) or water-in-water-in-water (W/W/W) multiple emulsions. It is thus expected that we can fabricate more complex emulsions by using an aqueous three-phase system.

Enhanced CH/CH separation performance on MOF membranes through blocking defects and hindering framework flexibility by silicone rubber coating.

The polydimethylsiloxane (PDMS) coating penetrated into the underneath ZIF-8 polycrystalline membrane not only blocking the inter-crystalline defects but also hindering the flexibility of the ZIF-8 framework, resulting in an unusual and highly desired increase in the separation selectivity of the CH/CH mixture under high feeding pressures.

Amino-Functionalized ZIF-7 Nanocrystals: Improved Intrinsic Separation Ability and Interfacial Compatibility in Mixed-Matrix Membranes for CO /CH Separation.

Highly permeable and selective, as well as plasticization-resistant membranes are desired as promising alternatives for cost- and energy-effective CO separation. Here, robust mixed-matrix membranes based on an amino-functionalized zeolitic imidazolate framework ZIF-7 (ZIF-7-NH ) and crosslinked poly(ethylene oxide) rubbery polymer are successfully fabricated with filler loadings up to 36 wt%. The ZIF-7-NH materials synthesized from in situ substitution of 2-aminobenzimidazole into the ZIF-7 structure exhibit enlarged aperture size compared with monoligand ZIF-7.

Zinc-substituted ZIF-67 nanocrystals and polycrystalline membranes for propylene/propane separation.

Continuous ZIF-67 polycrystalline membranes with effective propylene/propane separation performances were successfully fabricated through the incorporation of zinc ions into the ZIF-67 framework. The separation factor increases from 1.4 for the pure ZIF-67 membrane to 50.

Cu-Catalyzed hydrophosphorylative ring opening of propargyl epoxides: highly selective access to 4-phosphoryl 2,3-allenols.

A novel CuI-catalyzed cross-coupling of propargyl epoxides with P(O)H compounds is disclosed. The reaction proceeded efficiently under mild conditions to give 4-phosphoryl 2,3-allenols in good to high yields with excellent selectivity. The utility of the products was demonstrated and a plausible mechanism was also proposed.

Convenient synthesis of allenylphosphoryl compounds via Cu-catalysed couplings of P(O)H compounds with propargyl acetates.

A novel Cu-catalysed substitution reaction of propargyl acetates with P(O)H compounds is developed to afford allenylphosphoryl compounds via C-P bond coupling in high yields under mild conditions. A plausible mechanism involving the nucleophilic interception of the Cu-allenylidene intermediates is proposed.