Aqueous-System-Enabled Spray-Drying Technique for the Synthesis of Hollow Polycrystalline ZIF‑8 MOF Particles

Zeolitic imidazolate framework-8 shares the same topology with sodalite zeolite but consists of Zn nodes bridged by imidazolate linkers to form a neutral open-framework structure. ZIF-8 has been recognized as a unique molecular sieving material with a flexible framework enabling interesting “gate-opening” functionality. Controlling the crystal size and shape is crucial for regulating the structural flexibilities and mass transport properties. The present study demonstrates that an aqueous-system-enabled spray-drying process enables the shape engineering of ZIF-8 with a hollow polycrystalline structure. It is notable that our synthesis route produces an amorphous zinc complex compound, which possesses a continuous random network partially with crystalline fillers, after spray drying followed by an amorphous-to-crystal transition via activation treatment using polar organic solvents. The size of primary ZIF-8 crystals consisting of secondary polycrystals depends on the kind of the organic solvent. The macro-/microscopic structures of hollow polycrystalline ZIF-8 significantly structurally enhanced the adsorption capacity and uptake rate. The large-scale, rapid production and enhanced adsorption performances make this continuous method a very promising candidate for industrial applications and shaping of MOF

Synthesis of Well-Defined Novel Reactive Block Polymers Containing a Poly(1,4-divinylbenzene) Segment by Living Anionic Polymerization

In order to synthesize a variety of block polymers having poly­(1,4-divinylbenzene) (PDVB) segments, the living anionic block polymerizations of DVB with styrene, 2-vinylpyridine (2VP), <i>tert</i>-butyl methacrylate (^tBMA), methyl methacrylate (MMA), <i>N</i>-(4-vinylbenzylidene)­cyclohexylamine (<b>1</b>), 2-(4′-vinylphenyl)-4,4-dimethyl-2-oxazoline (<b>2</b>), or 2,6-di-<i>tert</i>-butyl-4-methylphenyl 4-vinylbenzoate (<b>3</b>) were conducted in THF at −78 °C with the anionic initiator bearing K⁺ in the presence of a 10-fold excess of potassium <i>tert</i>-butoxide. With the sequential addition of DVB and each of these monomers, the following block polymers having PDVB segments were successfully synthesized: PS-<i>b</i>-PDVB, P2VP-<i>b</i>-PDVB, PDVB-<i>b</i>-P2VP, PDVB-<i>b</i>-P^tBMA, PDVB-<i>b</i>-P­(<b>1</b>), PDVB-<i>b</i>-P­(<b>2</b>), PDVB-<i>b</i>-P­(<b>3</b>), PS-<i>b</i>-PDVB-<i>b</i>-P^tBMA, PS-<i>b</i>-P2VP-<i>b</i>-PDVB-<i>b</i>-P^tBMA, and PS-<i>b</i>-PDVB-<i>b</i>-P2VP-<i>b</i>-P^tBMA. The resulting polymers are all novel block polymers with well-defined structures (predictable molecular weights and compositions and narrow molecular weight distributions) and possess reactive PDVB segments capable of undergoing several postreactions. Based on the results of such sequential block polymerizations, the anionic random copolymerization of DVB and 2VP, the polymerizability with (C₄H₉)₂Mg, and some other addition reactions, it was found that the comparable reactivity of the chain-end anions follows the sequence of PS^– > PDVB^– > P2VP^– > P^tBMA^–. Accordingly, the reactivity of the corresponding monomers increases as follows: styrene < DVB < 2VP < ^tBMA

Data_Sheet_1_Isolation and Cs+ resistance mechanism of Escherichia coli strain ZX-1.PDF

This research aims to elucidate the physiological mechanisms behind the accidental acquisition of high-concentration cesium ions (Cs+) tolerance of Escherichia coli and apply this understanding to develop bioremediation technologies. Bacterial Cs+ resistance has attracted attention, but its physiological mechanism remains largely unknown and poorly understood. In a prior study, we identified the Cs+/H+ antiporter TS_CshA in Microbacterium sp. TS-1, resistant to high Cs+ concentrations, exhibits a low Cs+ affinity with a Km value of 370 mM at pH 8.5. To enhance bioremediation efficacy, we conducted random mutagenesis of TS_cshA using Error-Prone PCR, aiming for higher-affinity mutants. The mutations were inserted downstream of the PBAD promoter in the pBAD24 vector, creating a mutant library. This was then transformed into E. coli-competent cells. As a result, we obtained a Cs+-resistant strain, ZX-1, capable of thriving in 400 mM CsCl—a concentration too high for ordinary E. coli. Unlike the parent strain Mach1™, which struggled in 300 mM CsCl, ZX-1 showed robust growth even in 700 mM CsCl. After 700 mM CsCl treatment, the 70S ribosome of Mach1™ collapsed, whereas ZX-1 and its derivative ΔZX-1/pBR322ΔAp remained stable. This means that the ribosomes of ZX-1 are more stable to high Cs+. The inverted membrane vesicles from strain ZX-1 showed an apparent Km value of 28.7 mM (pH 8.5) for Cs+/H+ antiport activity, indicating an approximately 12.9-fold increase in Cs+ affinity. Remarkably, the entire plasmid isolated from ZX-1, including the TS_cshA region, was mutation-free. Subsequent whole-genome analysis of ZX-1 identified multiple SNPs on the chromosome that differed from those in the parent strain. No mutations in transporter-related genes were identified in ZX-1. However, three mutations emerged as significant: genes encoding the ribosomal bS6 modification enzyme RimK, the phage lysis regulatory protein LysB, and the flagellar base component protein FlgG. These mutations are hypothesized to affect post-translational modifications, influencing the Km value of TS_CshA and accessory protein expression. This study unveils a novel Cs+ resistance mechanism in ZX-1, enhancing our understanding of Cs+ resistance and paving the way for developing technology to recover radioactive Cs+ from water using TS_CshA-expressing inverted membrane vesicles.</p

An Experimental Investigation of the Ion Storage/Transfer Behavior in an Electrical Double-Layer Capacitor by Using Monodisperse Carbon Spheres with Microporous Structure

Monodisperse carbon spheres with coefficient of variation less than 4% were successfully synthesized through polycondensation of resorcinol with formaldehyde in the presence of ammonia as a catalyst followed by carbonization in an inert atmosphere. The diameters of the carbon spheres can be tuned in the range of 220–1140 nm by adjusting the ammonia concentration in the precursor solutions. Although the particle size decreases with increasing ammonia concentrations, there is no large difference in the internal pore structure between the different-sized carbon spheres. The size-controlled monodisperse carbon spheres were used as a model material to understand the ion storage/transfer behavior in electrical double-layer capacitor (EDLC). The present study clearly indicates that the reducing the particle size and highly monodispersity in both size and shape were effective at reducing mass transport resistance and improving EDLC performance reliability

Highly Efficient and Selective Hydrogenation of Nitroaromatics on Photoactivated Rutile Titanium Dioxide

We report that photoactivated rutile titanium dioxide (TiO₂) catalyzes a highly efficient and selective hydrogenation of nitroaromatics with alcohol as a hydrogen source. Photoirradiation (λ >300 nm) of rutile TiO₂ suspended in alcohol containing nitroaromatics at room temperature and atmospheric pressure produces the corresponding anilines with almost quantitative yields, whereas common anatase and P25 TiO₂ show poor activity and selectivity. The Ti³⁺ atoms located at the oxygen vacancies on the rutile surface behave as the adsorption site for nitroaromatics and the trapping site for photoformed conduction band electrons. These effects facilitate rapid and selective nitro-to-amine hydrogenation of the adsorbed nitroaromatics by the surface-trapped electrons, enabling aniline formation with significantly high quantum yields (>25% at <370 nm). The rutile TiO₂ system also facilitates chemoselective hydrogenation of nitroaromatics with reducible substituents; several kinds of functionalized anilines are successfully produced with >94% yields

Gold Nanoparticles Located at the Interface of Anatase/Rutile TiO₂ Particles as Active Plasmonic Photocatalysts for Aerobic Oxidation

Visible-light irradiation (λ > 450 nm) of gold nanoparticles loaded on a mixture of anatase/rutile TiO₂ particles (Degussa, P25) promotes efficient aerobic oxidation at room temperature. The photocatalytic activity critically depends on the catalyst architecture: Au particles with <5 nm diameter located at the interface of anatase/rutile TiO₂ particles behave as the active sites for reaction. This photocatalysis is promoted via plasmon activation of the Au particles by visible light followed by consecutive electron transfer in the Au/rutile/anatase contact site. The activated Au particles transfer their conduction electrons to rutile and then to adjacent anatase TiO₂. This catalyzes the oxidation of substrates by the positively charged Au particles along with reduction of O₂ by the conduction band electrons on the surface of anatase TiO₂. This plasmonic photocatalysis is successfully promoted by sunlight exposure and enables efficient and selective aerobic oxidation of alcohols at ambient temperature

Photocatalytic Dehalogenation of Aromatic Halides on Ta₂O₅‑Supported Pt–Pd Bimetallic Alloy Nanoparticles Activated by Visible Light

Dehalogenation of aromatic halides is one important reaction for detoxification and organic synthesis. Photocatalytic dehalogenation with alcohol, a safe hydrogen source, is one promising method; however, systems reported earlier need UV irradiation. We found that Pt–Pd bimetallic alloy nanoparticles (ca. 4 nm) supported on Ta₂O₅ (PtPd/Ta₂O₅), on absorption of visible light (λ > 450 nm), efficiently promote dehalogenation with 2-PrOH as a hydrogen source. Catalytic dehydrogenation of 2-PrOH on the alloy in the dark produces hydrogen atoms (H) on the particles. Photoexcitation of d electrons on the alloy particles by absorbing visible light produces hot electrons (e_hot^–). They efficiently reduce the adsorbed H atoms and produce hydride species (H^–) active for dehalogenation. The catalytic activity depends on the Pt/Pd mole ratio; alloy particles consisting of 70 mol % of Pt and 30 mol % of Pd exhibit the highest activity for dehalogenation

Titanium Dioxide/Reduced Graphene Oxide Hybrid Photocatalysts for Efficient and Selective Partial Oxidation of Cyclohexane

Partial oxidation of cyclohexane (CHA) to cyclohexanone (CHA-one) with molecular oxygen (O₂) is one of the most important reactions. Photocatalytic oxidation has been studied extensively with TiO₂-based catalysts. Their CHA-one selectivities are, however, insufficient because the formed CHA-one is subsequently decomposed by photocatalysis involving the reaction with superoxide anion (O₂^●–) produced by one-electron reduction of O₂ on TiO₂. Here we report that TiO₂, when hybridized with reduced graphene oxide (rGO), catalyzes photooxidation of CHA to CHA-one with enhanced activity and selectivity under UV light (λ > 300 nm). The TiO₂/rGO hybrids produce CHA-one with twice the amount formed on bare TiO₂ with much higher selectivity (>80%) than that on bare TiO₂ (ca. 60%). The conduction band electrons photoformed on TiO₂ are transferred to rGO, promoting efficient charge separation and enhanced photocatalytic cycles. The trapped electrons on rGO selectively promote two-electron reduction of O₂ and suppress one-electron reduction. This inhibits the formation of O₂^●–, which promotes photocatalytic decomposition of the CHA-one formed. These properties of rGO therefore facilitate efficient and selective formation of CHA-one on the hybrid catalyst

Vapor-Phase Synthesis of ZIF‑8 MOF Thick Film by Conversion of ZnO Nanorod Array

ZIF-8 metal organic framework “micrometer-thick” films were constructed from ZnO precursor by a vapor-phase synthesis. The ZnO-to-ZIF-8 crystal transformation proceeded in the presence of 2-methylimidazole (Hmim) vapor. Continuous coatings of intergrown ZIF-8 crystals require control of a nucleation density. The dependence of ZnO crystal plane on the ZnO-to-ZIF-8 crystal transformation was investigated using four bulk ZnO single crystals: <i>a</i>-plane (11–20), <i>c</i>-plane (0001), <i>m</i>-plane (10–10), and <i>r</i>-plane (10–11). It was revealed that the <i>m</i>-plane (10–10) of ZnO is more effectively transformed into ZIF-8. In this work, highly oriented ZnO nanorod array film was used to provide the transport pathway of Hmim molecules and volume expansion space of ZnO-to-ZIF-8 crystal transformation for nucleation and crystal intergrowth. The high conversion of ZnO nanorod array into ZIF-8 in a short time could be achieved because (1) such mass transfer is easy due to the uniform internanorod distance being maintained during reaction and (2) the surface of the nanorod array is dominated by the highly reactive <i>m</i>-plane (10–10)

Effects of Surface Defects on Photocatalytic H₂O₂ Production by Mesoporous Graphitic Carbon Nitride under Visible Light Irradiation

Photocatalytic production of hydrogen peroxide (H₂O₂) from ethanol (EtOH) and molecular oxygen (O₂) was carried out by visible light irradiation (λ > 420 nm) of mesoporous graphitic carbon nitride (GCN) catalysts with different surface areas prepared by silica-templated thermal polymerization of cyanamide. On these catalysts, the photoformed positive hole oxidize EtOH and the conduction band electrons localized at the 1,4-positions of the melem unit promote two-electron reduction of O₂ (H₂O₂ formation). The GCN catalysts with 56 and 160 m² g^–1 surface areas exhibit higher activity for H₂O₂ production than the catalyst prepared without silica template (surface area: 10 m² g^–1), but a further increase in the surface area (228 m² g^–1) decreases the activity. In addition, the selectivity for H₂O₂ formation significantly decreases with an increase in the surface area. The mesoporous GCN with larger surface areas inherently contain a larger number of primary amine moieties at the surface of mesopores. These defects behave as the active sites for four-electron reduction of O₂, thus decreasing the H₂O₂ selectivity. Furthermore, these defects also behave as the active sites for photocatalytic decomposition of the formed H₂O₂. Consequently, the GCN catalysts with relatively large surface area but with a small number of surface defects promote relatively efficient H₂O₂ formation