Bifunctional Cu-incorporated carbon nanospheres via in-situ complexation strategy as efficient toluene adsorbents and antibacterial agents.

Carbon adsorbents have been widely used to remove indoor volatile organic compounds (VOCs), however, the proliferation of bacteria on the carbon adsorbents may deteriorate the indoor air quality and thus pose a serious threat to human health. Herein, we report the synthesis of antibacterial porous carbon spheres (carbonized aminophenol-formaldehyde resin, CAF) with well-dispersed Cu species via an in situ incorporation of Cu2+ during the polymerization of 3-aminophenol-formaldehyde resin followed by a thermal carbonization and reduction process. Compared with CAF, the Cu/CAF-x nanocomposites with Cu loading show a much higher specific surface area (>700 m2 g-1vs. 569 m2 g-1 for CAF). In addition, the pore size of Cu/CAF-x is ranging from 0.7 to 1.68 nm, which is exactly conducive to adsorb the toluene molecules. As a result, the toluene adsorption capacity is improved from 123.50 mg g-1 for CAF to >170 mg g-1 for Cu/CAF-x. More importantly, such adsorbents possess excellent antibacterial performance, the Cu/CAF-10 (10 wt% of Cu loading) with a concentration of 50 µg mL-1 can completely kill the E. coli within 30 min. Our work paves the way to the development of bifunctional adsorbents with both efficient VOCs adsorption and excellent antibacterial performance.

High-efficiency Electroreduction of O2 into H2 O2 over ZnCo Bimetallic Triazole Frameworks Promoted by Ligand Activation.

Co-based metal-organic frameworks (MOFs) as electrocatalysts for two-electron oxygen reduction reaction (2e- ORR) are highly promising for H2 O2 production, but suffer from the intrinsic activity-selectivity trade-off. Herein, we report a ZnCo bimetal-triazole framework (ZnCo-MTF) as high-efficiency 2e- ORR electrocatalysts. The experimental and theoretical results demonstrate that the coordination between 1,2,3-triazole and Co increases the antibonding-orbital occupancy on the Co-N bond, promoting the activation of Co center. Besides, the adjacent Zn-Co sites on 1,2,3-triazole enable an asymmetric "side-on" adsorption mode of O2 , favoring the reduction of O2 molecules and desorption of OOH* intermediate. By virtue of the unique ligand effect, the ZnCo-MTF exhibits a 2e- ORR selectivity of ≈100 %, onset potential of 0.614 V and H2 O2 production rate of 5.55 mol gcat -1 h-1 , superior to the state-of-the-art zeolite imidazole frameworks. Our work paves the way for the design of 2e- ORR electrocatalysts with desirable coordination and electronic structure.

Nitrogen- and Halogen-Free Multifunctional Polymer-Directed Fabrication of Aluminum-Rich Hierarchical MFI Zeolites.

Aluminum-rich hierarchical MFI-type zeolites with high acidic-site density exhibit excellent activity and selectivity in bulky molecule-involved reactions. However, it is challenging to develop a facile and environmentally benign method for fabricating them. Herein, we employ a polymer that does not contain nitrogen and halogen elements to successfully synthesize aluminum-rich hierarchical ZSM-5 zeolite with a Si/Al ratio of 8 and a significant number of mesopores comprised of oriented-assembled nanocrystals. It is demonstrated that the nitrogen- and halogen-free polymer is instrumental in the formation of the ZSM-5 zeolite by serving as a template for constructing the hierarchical micro/mesoporous structure. Moreover, this polymer also acts as a crystal growth modifier to form a single-crystalline zeolite. Notably, the resultant zeolite shows a better catalytic performance in converting waste plastic into hydrocarbons than a commercial one. Our work enables the synthesis of high-quality hierarchical zeolites without requiring quaternary ammonium templates.

Selective adsorption of Co(II)/Mn(II) by zeolites from purified terephthalic acid wastewater containing dissolved aromatic organic compounds and metal ions.

Selective separation and recovery of Co(II)/Mn(II) from purified terephthalic acid (PTA) production wastewater is very important to reduce the Co(II)/Mn(II) catalysts consumption and control the pollutant discharge. This work employed zeolites NaA, NaX, and HZSM-5 with different pore sizes and Na(I) contents to selectively separate and recover Co(II)/Mn(II) from PTA wastewater and to understand the adsorption mechanism. It is found that only NaA can exclusively adsorb Co(II)/Mn(II) through ion-exchange without adsorbing any aromatic organic compound (AOC); oppositely, HZSM-5 shows the highest adsorption capacity for AOCs but almost no adsorption for Co(II)/Mn(II); and NaX exhibits moderate adsorption capacities for both Co(II)/Mn(II) and AOCs. Moreover, pH can significantly impact the adsorption of both Co(II)/Mn(II) and AOCs due to the competitive adsorption between H(I) and Co(II)/Mn(II) and the electrostatic repulsion between AOCs and zeolites. The adsorption kinetics, isotherms, and thermodynamics were also investigated to lay a good basis for process development. Importantly, bench-scale experiments for simulating the industrial operation were carried out, and the results show that the adsorption capacity of the NaA particles for Co(II)/Mn(II) from the industrial PTA wastewater is 9.1/8.6 mg/g, respectively, without adsorbing any AOC. Therefore, an efficient strategy to selectively separate and recover Co(II)/Mn(II) from PTA wastewater was successfully developed.

Understanding Catalyst Surfaces during Catalysis through Near Ambient Pressure X-ray Photoelectron Spectroscopy.

Heterogeneous catalysis occurs on the surface of a catalyst particle in a gas or liquid environment of reactants. The surface of the catalyst particle acts as an active chemical agent directly participating in a chemical reaction performed at a solid-gas or solid-liquid interface. Thus, authentic surface chemistry and the structure of a catalyst particle during catalysis are key descriptors for understanding catalytic performance of this catalyst. However, identification of the authentic surface of a catalyst particle during catalysis is not a simple task. We are far from knowing the fact. Photoelectron spectroscopy is one of the main techniques for characterizing surface of a catalyst since it's a surface sensitive technique. When used to track the surface of a catalyst particle at relatively high temperature in gas phase in the torr pressure range, it is called near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) or AP-XPS for simplicity. In the last several years, AP-XPS has been used to observe surface chemistry of catalysts of single crystals and nanoparticles of metal, metal oxide, and carbide. In this review, instrumentation of the near ambient pressure X-ray photoelectron spectrometers and observation of catalyst surfaces in gases phase under reaction conditions and during catalysis with AP-XPS are discussed with the following objectives: (1) to present how the surface of a catalyst particle can be characterized in gas phase, (2) to interpret how surface chemistries observed during catalysis are correlated with measured catalytic performances, (3) to demonstrate how the uncovered correlations between surface structures and catalytic performances help to understand catalytic mechanisms at a molecular level, and (4) to discuss challenges and prospects of using AP-XPS to explore the authentic surface of a catalyst under a condition near to an industrial catalytic condition. This review focuses on the application of AP-XPS to studies of catalysis and how the insights gained from AP-XPS studies can be used to achieve fundamental understanding of the catalytic mechanism at a molecular level.

Grid-like Neural Representations Support Olfactory Navigation of a Two-Dimensional Odor Space.

Searching for food, friends, and mates often begins with an airborne scent. Importantly, odor concentration rises with physical proximity to an odorous source, suggesting a framework for orienting within olfactory landscapes to optimize behavior. Here, we created a two-dimensional odor space composed purely of odor stimuli to model how a navigator encounters smells in a natural environment. We show that human subjects can learn to navigate in olfactory space and form predictions of to-be-encountered smells. During navigation, fMRI responses in entorhinal cortex and ventromedial prefrontal cortex take the form of grid-like representations with hexagonal periodicity and entorhinal grid strength scaled with behavioral performance across subjects. The identification of olfactory grid-like codes with 6-fold symmetry highlights a unique neural mechanism by which odor information can be assembled into spatially navigable cognitive maps, optimizing orientation, and path finding toward an odor source.

Tailored Design of Differently Modified Mesoporous Materials To Deeply Understand the Adsorption Mechanism for Polycyclic Aromatic Hydrocarbons.

A series of SBA-15 with different modifications have been successfully prepared and applied as adsorbents to remove polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions. The morphology and structural properties of the chemically modified materials are all similar to those of pure SBA-15, and thus the difference of PAHs adsorption capacity can be directly attributed to the different functional groups, which is favorable to deeply explore the adsorption mechanism. Adsorption kinetics and isotherm experiments for naphthalene (Nap), anthracene (Ant), and pyrene (Pyr) were carried out, and the results reveal that the adsorption processes follow a pseudo-second-order rate equation and the equilibrium can be achieved within 120 min for Nap and Ant, whereas only 90 min for Pyr, indicating that the more hydrophobic molecules, the easier and faster adsorption can be obtained. All of the adsorption isotherms fit well with the Freundlich model, suggesting the unevenly distributed active sites on adsorbents. The phenyl-functionalized materials possess the highest adsorption capacity, implying that the π-π interaction is the most primary interaction and plays the predominant role in the studied PAHs adsorption, superior to the acidic and hydrophobic interaction. Our research sheds light on the design and synthesis of advanced and highly efficient adsorbents to remove PAHs from aqueous solutions.

Synthesis of Pd/SiO2 Catalysts in Various HCl Concentrations for Selective NBR Hydrogenation: Effects of H+ and Cl- Concentrations and Electrostatic Interactions.

A series of silica supported Pd (Pd/SiO2) catalysts were prepared in various HCl concentrations (C HCl) of the impregnation solution with different electrostatic interactions between Pd precursor and support, and their catalytic properties were evaluated by the selective hydrogenation of nitrile butadiene rubber (NBR). The results show that with the C HCl increasing from 0.1 to 5 M, the particle size of Pd nanoparticles dramatically decreases from 24.2 to 5.1 nm and stabilizes at ∼5 nm when C HCl is higher than 2 M. Using the catalysts prepared with a high C HCl (>2 M), an excellent hydrogenation degree (HD) of ∼94% with 100% selectivity to C=C can be acquired under mild conditions. Interestingly, the HD could be remarkably increased from 65 to 92% by increasing only C Cl - from 0.1 to 2 M with the addition of NaCl while keeping C H + at 0.1 M. This is because PdCl4 2- is the predominant existing form of precursor at high C Cl - , which has a strong electrostatic attraction with the positively charged support favorable for the formation of small-sized Pd nanoparticles over silica. Notably, Pd leaching behavior during the hydrogenation reaction is closely related to C H + , and the higher the C H + , the less Pd residues are detected in the hydrogenated NBR. Our contribution is to provide a facile strategy to synthesize effective and stable Pd/SiO2 catalysts via adjusting the electrostatic interaction, which exhibits a high activity and selectivity for NBR hydrogenation.

The role of piriform associative connections in odor categorization.

Distributed neural activity patterns are widely proposed to underlie object identification and categorization in the brain. In the olfactory domain, pattern-based representations of odor objects are encoded in piriform cortex. This region receives both afferent and associative inputs, though their relative contributions to odor perception are poorly understood. Here, we combined a placebo-controlled pharmacological fMRI paradigm with multivariate pattern analyses to test the role of associative connections in sustaining olfactory categorical representations. Administration of baclofen, a GABA(B) agonist known to attenuate piriform associative inputs, interfered with within-category pattern separation in piriform cortex, and the magnitude of this drug-induced change predicted perceptual alterations in fine-odor discrimination performance. Comparatively, baclofen reduced pattern separation between odor categories in orbitofrontal cortex, and impeded within-category generalization in hippocampus. Our findings suggest that odor categorization is a dynamic process concurrently engaging stimulus discrimination and generalization at different stages of olfactory information processing, and highlight the importance of associative networks in maintaining categorical boundaries.

One-pot synthesis of hierarchical FeZSM-5 zeolites from natural aluminosilicates for selective catalytic reduction of NO by NH3.

Iron-modified ZSM-5 zeolites (FeZSM-5s) have been considered to be a promising catalyst system to reduce nitrogen oxide emissions, one of the most important global environmental issues, but their synthesis faces enormous economic and environmental challenges. Herein we report a cheap and green strategy to fabricate hierarchical FeZSM-5 zeolites from natural aluminosilicate minerals via a nanoscale depolymerization-reorganization method. Our strategy is featured by neither using any aluminum-, silicon-, or iron-containing inorganic chemical nor involving any mesoscale template and any post-synthetic modification. Compared with the conventional FeZSM-5 synthesized from inorganic chemicals with the similar Fe content, the resulting hierarchical FeZSM-5 with highly-dispersed iron species showed superior catalytic activity in the selective catalytic reduction of NO by NH3.

New insight into ordered cage-type mesostructures and their pore size determination by electron tomography.

In this work, a new approach based on electron tomography (ET) has been developed to measure the pore size, through which new insight into cage-type ordered mesostructures and their pore size determination has been obtained. It is demonstrated that the accurate pore diameter, especially for cage-type cubic mesoporous materials, can be determined only through our ET approach by considering that the pore geometry is a real 3D space. We use the established ET method to revisit the applicability of different models for the pore size calculation in nitrogen adsorption analysis. Different from the overwhelming understanding that the nonlocal density functional theory (NLDFT) and Derjaguin-Broekhoff-de Boer (BdB) model are recommended to calculate the pore size of cage-type cubic mesoporous materials while the Barret-Joyner-Halenda (BJH) model should not be used, a new understanding is gained through this study. The choice of a suitable model for pore size determination depends on the precise pore structure. For a cage-type cubic mesoporous material with fcc symmetry and a large entrance connecting the cages, the BJH model is more accurate while the other two methods overestimate the pore size (by up to 40%). The DFT model is more appropriate when the pore shape is a perfect sphere than the BJH model, which underestimates the pore size, and the BdB model, which overestimates the pore size. It is our opinion that the unique ET approach should be used to revisit a vast number of large-pore cubic mesoporous materials to provide genuine structural information.

A designated odor-language integration system in the human brain.

Odors are surprisingly difficult to name, but the mechanism underlying this phenomenon is poorly understood. In experiments using event-related potentials (ERPs) and functional magnetic resonance imaging (fMRI), we investigated the physiological basis of odor naming with a paradigm where olfactory and visual object cues were followed by target words that either matched or mismatched the cue. We hypothesized that word processing would not only be affected by its semantic congruency with the preceding cue, but would also depend on the cue modality (olfactory or visual). Performance was slower and less precise when linking a word to its corresponding odor than to its picture. The ERP index of semantic incongruity (N400), reflected in the comparison of nonmatching versus matching target words, was more constrained to posterior electrode sites and lasted longer on odor-cue (vs picture-cue) trials. In parallel, fMRI cross-adaptation in the right orbitofrontal cortex (OFC) and the left anterior temporal lobe (ATL) was observed in response to words when preceded by matching olfactory cues, but not by matching visual cues. Time-series plots demonstrated increased fMRI activity in OFC and ATL at the onset of the odor cue itself, followed by response habituation after processing of a matching (vs nonmatching) target word, suggesting that predictive perceptual representations in these regions are already established before delivery and deliberation of the target word. Together, our findings underscore the modality-specific anatomy and physiology of object identification in the human brain.

Highly ordered cubic mesoporous materials with the same symmetry but tunable pore structures.

In this article, two highly ordered mesoporous silica materials with the same face-centered cubic (fcc) symmetry but distinctly different pore structures have been synthesized by simply changing the amount of silica source. Their structures have been extensively studied by Synchrotron small-angle X-ray scattering, N(2) sorption analysis, scanning and transmission electron microscopy observations, and electron tomography. One mesoporous material formed by a hard sphere packing (HSP) pathway exhibits a bimodal pore distribution, while the other has a conventional FDU-12-type mesostructure with a single-sized pore. By increasing the amount of the silica source, the cavities formed by the packing of composite spherical micelles in the HSP mesostructure are gradually filled by the excess of siliceous species, leading to the conventional FDU-12-type mesostructure with the disappearance of bimodal pores. The pore connectivity of the HSP mesoporous material hydrothermally treated at 150 °C has been further investigated. Taking advantage of the ultrathin tomographic slices, the sizes of cage, cavity, and connectivity are measured to be 14.5, 10.5, and 6.4 nm, respectively. More importantly, the pore connection between the cage and cavity is directly observed to occur along the ⟨100⟩ direction, different from the FDU-12-type mesostructure in which the connection appears between two adjacent cages along the ⟨110⟩ direction. This work represents an unusual example where two ordered cage-type mesoporous materials with the same symmetry can be synthesized by slightly changing the synthesis condition, but their pore structures and pore connections are significantly different. Our finding is important for understanding the formation mechanism and for the rational design and controllable synthesis of novel mesoporous materials.

Acidity adjustment of HZSM-5 zeolites by dealumination and realumination with steaming and citric acid treatments.

This article describes a novel method for acidity adjustment of HZSM-5 zeolites with steaming and citric acid treatments and demonstrates the realumination effect of citric acid on HZSM-5 zeolites dealuminated by steaming. A series of modified HZSM-5 zeolites were prepared by streaming and/or acid treatments and characterized by means of X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), (27)Al MAS NMR spectroscopy, hydroxyl infrared spectroscopy (OH-IR), pyridine-adsorbed infrared spectroscopy, and N(2) adsorption in the present investigation. The results showed that compared with single HCl or citric acid treatment, steaming treatment, and steaming/HCl treatments, citric acid treatment after steaming exclusively increased the amount of framework Al due to reinsertion of extraframework Al into the defective sites of the steamed HZSM-5 framework. This realumination effect of the citric acid treatment on the steamed HZSM-5 zeolite, which is reported here for the first time to the best of our knowledge, could nearly recover the pore structure of the steamed zeolite to that of the parent HZSM-5 zeolite and appropriately tailor the amount and strength of different acid sites, which sheds light on optimizing the physicochemical properties of HZSM-5 zeolites. It was also found that the steaming treatment prior to the citric acid treatment was the precondition of the realumination of HZSM-5 zeolites, suggesting that the lattice defect sites generated during steaming were necessary for citric acid to work.