Adsorption Centers Research Articles

Polyamine functionalized cage hollow mesoporous SiO2 microspheres for CO2 capture over a wide temperature range

Hollow SiO2 microspheres have become attractive materials for nanotechnology applications owing to their biological inertness and high functionality. In this study, hydrophobic spherical hollow cages were formed using the soft stencil method with Pluronic F127 and cetyltrimethylammonium bromide (CTAB) as the structure-directing agent, and hollow nanoporous SiO2 microspheres (FHMS) were prepared using the soft template method. Various of amine functionalization modes were further employed to demonstrate the complexity of the relationship between pore structure/amidation mode/amine content and adsorption capacity. The hollow morphology of the porous silica was revealed using field-emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and its porous properties were revealed using nitrogen adsorption-desorption isotherm measurements. Experiments on the fixed-bed dynamic adsorption process at 15% CO2 showed that the high specific surface area, high pore volume and amine content of the carriers had a positive effect on the adsorption performance. However, the accessibility of the adsorption centre was affected at high loadings, and the amine efficiency and adsorption capacity were reduced. The dual amine functionalized FHMS-G-I60 maintained the integrity and order of the hollow mesoporous carrier structure, and overcame the dilemma of easy loss in the cycle process of the impregnation method and the low adsorption capacity of the grafting method. It possessed an adsorption capacity of 3.62 mmol/g, high adsorption cycling stability (more than 99.5% adsorption maintained after 10 cycles) and high amine efficiency (0.2852 mmol CO2/mmol N). CO2-TPD analysis (Thermal Programmed Desorption) further showed that FHMS-G-I60 had a faster desorption rate and lower regeneration energy consumption. In general, such structure-directed prepared matrices and functionalized with different amines are promising and low-cost adsorbents that can be used to capture CO2 from ambient air and flue gases under different demands.

Stabilizing LiNi0.8Co0.1Mn0.1O2 cathode by combined moisture and HF digestion/adsorption for high-performance lithium metal batteries

Nickel-rich layered oxide cathodes such as LiNi0.8Co0.1Mn0.1O2 are promising to significantly increase the energy density of lithium metal batteries beyond 350 Wh kg−1. However, serious issues regarding cycle stability still remain when matching with conventional non-aqueous carbonate electrolytes that contain fluorine such as lithium hexafluorophosphate (LiPF6). Hydrolysis of LiPF6 generates corrosive hydrofluoric acid (HF), which destroys the cathode structure and accelerates the cathodic dissolution/anodic deposition of transition metal (TM) ions. Here, we demonstrate that ball milling NCM811 with carbon-coated aluminum nitride (AlN-C) remarkably enhances the capacity retention. AlN-C acts both as a scavenger and as an adsorption center to digest and adsorb H2O and HF, respectively. Thereby, it prevents the dissolution of TM ions, which would result in capacity decay and damage to the lithium metal anode. It is demonstrated that the addition of AlN-C via wet ball milling with NCM811 enables retaining a specific capacity of 149.9 mA h g−1 after 250 cycles (capacity retention: 85.2 %) at 1 C even in a high moisture electrolyte containing ∼0.2 % (v/v) H2O. Therefore, this work shows up a pathway to a rational enhancement of the capacity retention and cycle life of nickel-rich cathodes.

Biomass-Derived Carbon Quantum Dots Chemical Bonding with Sn-Doped Bi2O2CO3 Endowed Fast Carriers' Dynamics and Stabilized Oxygen Vacancies for Efficient Decontamination of Combined Pollutants.

Surface defects on photocatalysts could promote carrier separation and generate unsaturated sites for chemisorption and reactant activation. Nevertheless, the inactivation of oxygen vacancies (OVs) would deteriorate catalytic activity and limit the durability of defective materials. Herein, bagasse-derived carbon quantum dots (CQDs) are loaded on the Sn-doped Bi2O2CO3 (BOC) via hydrothermal procedure to create Bi─O─C chemical bonding at the interface, which not only provides efficient atomic-level interfacial electron channels for accelerating carriers transfer, but also enhances durability. The optimized Sn-BOC/CQDs-2 achieves the highest photocatalytic removal efficiencies for levofloxacin (LEV) (88.7%) and Cr (VI) (99.3%). The elimination efficiency for LEV and Cr (VI) from the Sn-BOC/CQDs-2 is maintained at 55.1% and 77.0% while the Sn-BOC is completely deactivated after four cycle tests. Furthermore, the key role of CQDs in stabilization of OVs is to replace OVs as the active center of H2O and O2 adsorption and activation, thereby preventing reactant molecules from occupying OVs. Based on theoretical calculations of the Fukui index and intermediates identification, three possible degradation pathways of LEV are inferred. This work provides new insight into improving the stability of defective photocatalysts.

Homogeneous heterophase junction based on cubic/orthomorphic SnS for chemiresistive room temperature trace-ethanol sensor

Herein, we developed a homogeneous heterophase structure based on the stereochemically-active cubic/orthorhombic SnS (CUB/ORT-SnS) by chemical precipitation and vacuum annealing. By precisely adjusting the annealing temperature, spherical cubic-SnS partially transformed into block-like orthorhombic phase. In the constructed heterophase structure, abundant junction interfaces which directly exposed in the atmosphere, serve as high-active adsorption centers, effectively hoisting the ethanol adsorption capability of SnS. The experimental results show that CUB/ORT-SnS sensor exhibits a response of 184% towards 5 ppm ethanol with rapid response-recovery process at room temperature (RT). Moreover, in order to improve the selectivity of the sensor to ethanol vapor, principal component analysis (PCA) was adopted to realize the specific identification towards ethanol and isopropanol. Further investigations based on DFT calculations and band alignment indicate that local cubic phase SnS of the heterophase structure is the strong electron trap, and forms effective conductive path with ethanol molecules. Benefiting from the enrichment of the interface adsorption sites and the enhancement of carrier transport and diffusion, the heterophase junction of SnS obtains remarkably boosted ethanol-sensing performance. This work constructs a homogeneous heterophase structure for sensing ethanol at RT, which provides a new design strategy for developing high-performance VOCs gas sensors.

Effects of cage topology on ethylene adsorption mechanism in silver exchanged CHA and RHO zeolites: An Inelastic Neutron Scattering and Density Functional study

Zeolite-based adsorbents have been successfully used for many challenging separations due to their tunable properties. A particularly notable application involves the separation of light olefins from paraffins, wherein the molecular sieving properties of zeolites play a pivotal role. Additionally, the selective interaction of alkenes with transition metal cations, positioned within the channels and cavities of microporous zeolites, further enhances separation capabilities.This study aims to comprehensively characterize the interactions between ethylene and Ag+ exchanged zeolites, employing a multidisciplinary approach, combining Inelastic Neutron Scattering (INS), Infrared (IR) spectroscopy, Nuclear Magnetic Resonance (NMR), UV–Vis and Density Functional Theory (DFT) calculations. CHA and RHO, zeolites largely applied in gas separation processes, were chosen due to their similar small pore sizes and pore volume, but different cavity shapes and flexibilities.The interpretation of derived DFT Electron Density Difference, experimentally supported by 13C Solid State NMR results, provide an understanding of each framework’s role during the charge transfer mechanisms between ethylene and transition metal species. Specific deformations in the flexible framework of zeolite RHO explain a blueshift of the band at 400 cm−1 in the librational region of INS spectra compared to CHA. This structural change in RHO, represented by the conic shape of the cage 8-ring side pockets, increases steric effects over the adsorbate while rendering the metallic adsorption center less exposed within the zeolite’s cavity, finally leading to a weaker adsorption energy. The redshift of C=C stretching frequencies observed by IR spectroscopy and DFT calculations, as well as C=C and C-H bond lengthening of ethylene confirm the formation of π-complexes on silver in both zeolites and allowed a further evaluation of the effects of the different frameworks cages on the aforementioned interaction.

ВЛИЯНИЕ ХИМИЧЕСКИХ СПОСОБОВ МОДИФИКАЦИИ НА АДСОРБЦИОННЫЕ ХАРАКТЕРИСТИКИ СЛОИСТЫХ СИЛИКАТОВ БЕНТОНИТА

This paper presents the results that allow us to establish the effectiveness of treatments of layered silicates on the example of low-quality alkaline earth bentonite from the Nurlat deposit of the Republic of Tatarstan from the point of view of improving their adsorption properties. The effect of treatments with sulfuric acid solution, sodium carbonate and amorphous silica on the adsorption and structural characteristics of bentonite has been studied. A comparative assessment of the adsorption index for methylene blue bentonites of various deposits is given. The research results showed that the modification of bentonite from the Nurlat deposit with a solution of sulfuric acid and sodium carbonate contributes to the transformation of its adsorption and structural properties, in particular, an increase in the adsorption index and cation exchange capacity by 25 and 40%, respectively. Therefore, modification with sodium carbonate is preferable to activation with sulfuric acid for the studied bentonite deposit, especially given the low cost and concentration of the salt reagent. Under conditions of combining chemical effects on the raw material composition, the increase in adsorption capacity reaches 80%. These transformations of properties are the result of changes in the ion-exchange complex of layered silicates, an increase in the centers of adsorption and their energy. Adsorption-desorption isotherms for nitrogen molecules have been obtained, which are classified as types II and III in accordance with the classification of Brunauer, Emmet and Teller, which indicates a polymolecular adsorption mechanism and a predominantly meso- and macroporous structure of the studied bentonite deposit. It was found that the pore space of bentonite of both basic and modified composition is mainly represented by mesopores with an average diameter of 3,8 nm according to BJH and a volume of 0,057 and 0,068 cm3/g, respectively.

N-Type boron β-diketone-containing conjugated polymers for high-performance room temperature ammonia sensors.

Organic semiconductor (OSC) gas sensors with good mechanical flexibility have received considerable attention as commercial and wearable devices. However, due to poor resistance to moisture and low conductivity, the improvement in the sensing capability of individual OSCs is limited. Reported here is a promising pathway to construct a series of conjugated organic polymers (COPs) with well-defined pyrimidine (Py-COP) or boron β-diketone (BF-COP) units. Unlike traditional metal- or carbon-based hybrid materials, the developed COPs can provide abundant absorption sites for gaseous analytes. As a result, the as-prepared BF-COP results in an excellent sensing response of over 1500 (Ra/Rg) toward 40 ppm of NH3 at room temperature, which is the highest value among those of pristine COPs as n-type sensing materials. Notably, they can maintain their initial sensing responses for two months and 90% relative humidity resistance. Combining the results of in situ Fourier transform infrared spectroscopy and theoretical calculations, the β-diketone skeleton is found to activate the surface electronic environment, verifying that the electron-deficient B ← O groups are adsorption centers. The B/N-heterocyclic decoration effectively modulates the redox properties and electronic interactions, as well as perturbs charge transfer in typical π-conjugated COPs. These results offer insight into developing highly efficient OSC gas sensors, which potentially have broadened sensing applications in the areas of organoboron chemistry.

Comparative Analysis of Asphalt Forming Processes Based on Finely Dispersed Expanded Clay Powders

The features of the structure formation of an asphalt binder modified with a highly dispersed expanded clay powder are investigated. The viscosity of the modified asphalt binder and the formation of an adsorption layer of bitumen on the surface of the particles of the mineral component at various degrees of filling in the temperature range of 100–180oC have been studied. The effect of the impact of expanded clay powder on the adsorption activity of bitumen, the adhesive strength of bitumen with a mineral filler and on the adhesion of an asphalt binder with a mineral filler is analyzed. It was revealed that the interaction of bitumen with highly dispersed expanded clay powder significantly increases the viscosity of the asphalt binder and increases the thickness of the bitumen film on the surface of mineral particles at all process temperatures compared with standard limestone mineral powder, which is determined by the processes of selective diffusion of low-molecular hydrocarbons into the particles of expanded clay powder occurring when combined with the binder. Modification of the asphalt binder with expanded clay powder significantly increases its adsorption activity and adhesion of bitumen to mineral aggregate and adhesive strength at the interface of the «filler–bitumen» phases. This is due not only to physical interaction, but also to the presence of an increased number of active surface adsorption centers of Lewis and Brensted on the surface of expanded clay particles, which indicates the formation of chemical bonds.

Физико-химические трансформации сапонитсодержащего материала при его активации измельчением

Structural-phase transformations on the surface of powder systems of saponite-containing material after mechanical dispersion have been studied. The degree of crystallinity, adsorption capacity and specific surface energy depending on the time mode of grinding were used as compared information characteristics. It has been established that, despite the fact of the constancy of the degree of crystallinity, mechanical grinding of saponite-containing raw materials leads to its activation, which is expressed by a proportional increase in the sorption capacity of the obtained powders, an increase in the concentration of active adsorption centers and the value of the specific free surface energy. An increase in the time of mechanical grinding of a saponite-containing material leads to the production of samples with an increased (compared to the initial material) surface hydrophilicity.

Enhancing plasma-catalytic toluene oxidation: Unraveling the role of Lewis-acid sites on δ-MnO2

The emission of volatile organic compounds (VOCs) into the air, primarily due to human activities, has caused significant environmental pollution and health concerns. In response, the development of advanced environmental catalysts is crucial, and δ-MnO2 has emerged as a promising material for efficient VOC oxidation. However, the identification of the specific active sites and the underlying oxidation mechanisms of this material remain unclear, hindering the development and optimization of high-activity catalysts. Herein, we present a strategy to remove the internal water and hydrated cations from δ-MnO2, thereby unblocking the inter-lamellar gaps and exposing the internal Lewis-acid sites, while maintaining other physical and chemical characteristics of the sample unchanged. Notably, the well-defined δ-MnO2 catalysts with more accessible interlayer Lewis-acid sites exhibited significantly enhanced catalytic activity in toluene oxidation, demonstrated in both two-stage plasma catalysis and single-stage ozonation processes. A quantitative analysis of Lewis-acid sites and initial toluene reaction rates revealed that these Lewis-acid sites serve as the active centers for toluene adsorption and activation, and the heterogeneous reaction between toluene and ozone follows the Langmuir-Hinshelwood mechanism. Moreover, in-depth analysis of byproducts showed that δ-MnO2 rich in Lewis-acid sites promoted the oxidation of intermediates, such as esters, hydrazides, and ketones, leading to a more complete toluene oxidation. This work not only fully explores the potential of δ-MnO2 as a catalyst, but also provides valuable insights into the elucidation of unknown catalytic active sites, potentially paving the way for the rational design of more efficient catalysts for VOC oxidation.

Adsorption properties of the surface of Silochrome S-80 modified with aluminium alizarinate

Silica-based materials are widely used in the processes of concentration and separation of various organic substances. Successful use of SiO2 is due to its chemical resistance, thermal stability, the nature and distribution of functional groups on the surface, as well as the possibility of creating materials based on it with certain textural characteristics, which are regulated by synthesis conditions and surface modification. For the solution of specific problems of chromatography, it is necessary to obtain new adsorbents with fixed functional groups, layers or elements, by varying which the number and types of adsorption centres of the original surface change. Chelate complexes of transition metals, including those deposited in the form of adsorption layers, are used as promising modifying additives of particular interest. In this work, SiO2 based on Silochrome S-80, modified with aluminium alizarinate was studied by physicochemical method. Using thermogravimetry it was established that aluminium alizarinate is stable up to 270 °C. Using adsorption porosimetry, it was shown that modification of silica leads to a decrease in the average diameters and total volumes of pores, and specific surface areas from 84 to 79 m²/g. Using IR and Raman spectroscopy, the fixation of chelates on the surface of Silochrome was proven. The gas chromatographic method was used to study the adsorption processes of organic compounds (n-alkanes, nitromethane, heptene-1, aromatic hydrocarbons, ketones and alcohols) capable of various types of intermolecular interactions. The modification of silica with an alizarin-containing complex contributes to a change in the Henry adsorption constants and the contributions of specific interactions to the heat of adsorption. In this case, the highest values of ∆ q̅dif,1(special) are characteristic of organic compounds prone to donor-acceptor and π-complex formation. According to the analysis of compensation thermodynamic dependencies q̅dif,1 - ∆S̅S1,c it was shown that entropy is the determining thermodynamic parameter during the adsorption of test compounds on the surface of the studied chromatographic materials.

Enhanced dual-catalytic elimination of NO and VOCs by bimetallic oxide (CuCe/MnCe/CoCe) modified WTiO2 catalysts: Boosting acid sites and rich oxygen vacancy

It remains challenging to remove nitrogen oxides (NOx), benzene (C6H6), and toluene (C7H8) simultaneously under conditions of low oxygen and high SO2 concentration. Herein, CuCe, MnCe, and CoCe doped WTiO2 catalysts were designed. The prepared CuCe-WTiO2 catalyst consistently maintained more than 85% NO, 92% C6H6, and 91% C7H8 removal in 260–420 °C under 3.33% O2 and 1000 ppm SO2. The adequate charge flow between the catalyst surface and the gas molecules was enhanced, promoting SO2 tolerance of CuCe-WTiO2. More NH3, NH4+, and -NH2 were adsorbed with acid sites on the CuCe-WTiO2 surface. The high concentration of adsorption centers and superior redox properties effectively improved the co-catalytic efficiency. The primary intermediates in the reduction processes via the Langmuir-Hinshelwood and Eley-Rideal mechanisms were NO2, bridged nitrite (NO2–), and monodentate nitrite (NO2–). The generation of reactive chemisorbed oxygen (Oα) becomes more accessible with the transfer of electrons from Ce4+ to adsorbed O2. C6H6 and C7H8 are progressively oxidized by Oα and eventually completely mineralized to CO2 and H2O. This study is anticipated to offer a new option for co-catalytic removal of NO, C6H6, and C7H8.

Synchrotron-based techniques for elemental analysis in soil-plant system under polluted environment

Analytical techniques for elemental analysis in the soil-plant system have significance importance, especially emerging techniques such as synchrotron radiation (SR). Improved techniques allow samples to be examined in a non-invasive manner at high speed and resolution, resulting in better sample data. By applying various analytical techniques based on SR, it is possible to gather different information about the structure of the studied samples. In mining ecology, such techniques are widely used in assessing heavy metal-polluted sites, i.e., overburden dumps and areas around operating and mothballed mines. The present review elaborated insights into different analytical techniques for applying SR in plant-soil samples. The review also compared traditional research techniques with SR-based emerging and improved techniques. The need to use SR techniques for the complex diagnostics of sample structures to study their elemental and phase composition is substantiated. Using an integrated approach with SR, we can study the dynamics and speciation of HMs with carrier phases and uncover the mechanisms underlying the interactions between the adsorption centers of minerals, organic components, and heavy metals. It also improves the efficiency and accuracy of analysis and broadens the range of information obtained, which could lead to a more precise analysis of samples.

Oxide Glasses for Removal of Ammonia and Nitrogen Derivatives from Industrial Wastewater

Adsorption is a rapid and known method to treat wastewater and remove contaminants such as ammonia (NH3+) and nitrogen derivatives. Herein, novel adsorption materials are demonstrated to eliminate the most hazard industrial and municipal contaminants including ammonia and nitrogen derivatives. Oxide glasses as new adsorbing media are beneficial for wastewater treatment due to dangling bond defects and non-bridging oxygen, which act as adsorption centers. Oxide glasses are characterized by their low cost and simple preparation method. Different types of oxide glasses including borate, phosphate, silicate, and germinate glasses are used as adsorbents to estimate the glass type of the optimal removal efficiency. It is found that the higher removal efficiency is exhibited for both borate and silicate glasses. Therefore, by preparing hybrid borate-silicate (borosilicate) glass, the best efficiency is achieved. The influences of boundary conditions including contact time, adsorption temperature, and adsorbent dosage on the efficiency of adsorption process are demonstrated. The optimal removal efficiency is achieved when using borosilicate glass sample (as adsorbent) with contact time of 90 min, adsorption temperature of 70 °C, and adsorbent dosage of 1.5 mg/100 ml. Finally, by comparing our results with the previous adsorption treatment works, it is found that adsorption capacity of ammonia reached to 9.12 mg/g, which is a valid and acceptable value.

Se–Se bonds induced highly metallic 1T’ MoSe2.3 nanosheets cocatalysts towards boosted H2O2 photosynthesis over NH2-MIL-125 derived TiO2 nanotablets

Loading non-noble metal cocatalysts is a promising means to inhibit the photogenerated charge recombination and provide more active centers for surface photocatalytic reactions, especially for hydrogen peroxide (H2O2) generation. The H2O2 photosynthesize activity has shown to be seriously limited by secondary decomposition of synthesized H2O2, owing to the presence of metal-based active centers. Herein, highly metallic MoSe2.3 nanosheet with dominated 1T and 1T' phase were in-situ loaded onto the NH2-MIL-125(Ti) derived TiO2 nanotablets via a one-step hydrothermal method to form a TiO2/MoSe2.3 composite for enhancing photocatalytic H2O2 production activity. The abundant edge Se–Se bonds, along with the high content of 1T and 1T' phase endowed MoSe2.3 nanosheets with highly metallic property to function as an efficient cocatalyst to accelerate the carrier separation. Besides that, Se–Se bonds could offer more active centers for O2 adsorption to boost the generation of H2O2. As a result, the optimal TiO2/MoSe2.3 composite photocatalyst (TM-5) displayed a much enhanced H2O2 production performance of 891 µmol L–1 h−1 in isopropanol solution (IPA, 10 vol.%) under monochrome LED-(365 nm) light irradiation, 2.3 times higher than pure NH2-MIL-125 derived TiO2 nanotablets. This work would provide a feasible method in non-metal cocatalyst design for H2O2 photosynthesize.

Influence of chemical activation on the ability of Transcarpathian clinoptilolite to adsorb direct dyes

Significant quantities of wastewater are generated in dyes synthesis processes and in technologies involving their use, which are toxic to living organisms, making the purification of industrial wastewater from organic colouring substances a pressing issue nowadays. The aim of this study was to investigate the prospects of using natural clinoptilolite from the Sokyrnytske deposit and its activated forms in the purification processes of wastewater from direct dyes. Natural clinoptilolite was activated by treatment with 5% H2SO4 and HCl aqueous solutions and heating at 300°C for two hours. The impact of activation conditions on the structural adsorption properties of clinoptilolite has been determined using a comprehensive thermal analysis method. The adsorption of the direct violet dye by natural and activated clinoptilolite has been investigated using spectrophotometric methods at pH 7 and a light wavelength of 550 nm, corresponding to the maximum value of light absorption coefficient. According to the results of thermal analysis, activated clinoptilolite samples exhibited a more developed specific surface area and a higher presence of hydroxyl groups, which can serve as active adsorption sites on the surface. The results of the violet dye adsorption have corresponded to the monomolecular Langmuir theory, indicating the energetic homogeneity of the adsorption centres. By linearizing the Langmuir adsorption isotherm equation, adsorption characteristics of natural and activated clinoptilolite with a 5% HCl aqueous solution relative to the direct violet dye have been determined. Activated clinoptilolite has shown increased sorption capacity (9.53 mmol/kg) compared to natural clinoptilolite (2.28 mmol/kg). The improvement in adsorption characteristics of activated clinoptilolite has been explained by its partial dealumination, resulting in the appearance of meso- and macropores capable of retaining dye molecules. The use of a 30% H2SO4 aqueous solution in activation processes and heating above 400°C has caused mineral degradation, confirmed by electron images of its surface. Practical value of the study lies in the recommendation to apply activated clinoptilolite in the purification processes of wastewater from organic pollutants

Synthesis, Structural Versatility, Magnetic Properties, and I- Adsorption in a Series of Cobalt(II) Metal-Organic Frameworks with a Charge-Neutral Aliphatic (O,O)-Donor Bridge.

Four new metal-organic frameworks based on cobalt(II) salts and 1,4-diazabicyclo[2.2.2]octane N,N'-dioxide (odabco) were obtained. Their crystallographic formulae are [Co3(odabco)2(OAc)6] (1, OAc- = acetate), [Co(H2O)2(HCOO)2]·odabco (2), [Co2(H2O)(NO3)(odabco)5](NO3)3·3.65H2O (3), and [Co2(DMF)2(odabco)4](NO3)4·3H2O (4; DMF = N,N-dimethylformamide). Crystal structures of 1-4 were determined by single-crystal X-ray crystallography. Coordination polymer 1 comprises binuclear and mononuclear metal-acetate blocks alternating within uncharged one-dimensional chains, in which odabco acts as a bridging ligand. A layered Co(II) formate 2 contains odabco only as guest molecules located in the interlayer space. Layered compound 3 and three-dimensional 4 have cationic coordination frameworks with 26% and 34% specific void volumes, respectively, unveiling high structural diversity of Co(II)-odabco MOFs based on quite a rare aliphatic moiety. Magnetization measurements were performed for 1, 3, and 4 and the obtained data were interpreted on the basis of their crystal structures. A strong (J/kB~100 K) antiferromagnetic coupling was found within binuclear metal blocks in 1. Ion exchange experiments revealed a considerable iodide uptake by 3 resulting in an up to 75% guest nitrate substitution within the voids of a coordination framework, found by capillary zone electrophoresis data and confirmed by single-crystal XRD. A preservation of 3 crystallinity during the exchange allowed for the guest I- positions within a new adduct with the formula [Co2(H2O)(NO3)(odabco)5]I2(NO3)·1.85H2O (3-I) to be successfully determined and the odabco aliphatic core to be revealed as a main adsorption center for quite large and easily polarizable iodide anions. In summary, this work presents a comprehensive study for a series of 1,4-diazabicyclo[2.2.2]octane N,N'-dioxide-based MOFs of cobalt(II) within the framework of magnetic properties and reports the first example of anion exchange in odabco-based coordination networks, supported by direct X-ray structural data. The reported results unveil promising applications of such frameworks bearing ligands with an aliphatic core in the diverse structural design of selective adsorbents and other types of functional materials.

Metal to non-metal sites of metallic sulfides switching products from CO to CH4 for photocatalytic CO2 reduction

The active center for the adsorption and activation of carbon dioxide plays a vital role in the conversion and product selectivity of photocatalytic CO2 reduction. Here, we find multiple metal sulfides CuInSnS4 octahedral nanocrystal with exposed (1 1 1) plane for the selectively photocatalytic CO2 reduction to methane. Still, the product is switched to carbon monoxide on the corresponding individual metal sulfides In2S3, SnS2, and Cu2S. Unlike the common metal or defects as active sites, the non-metal sulfur atom in CuInSnS4 is revealed to be the adsorption center for responding to the selectivity of CH4 products. The carbon atom of CO2 adsorbed on the electron-poor sulfur atom of CuInSnS4 is favorable for stabilizing the intermediates and thus promotes the conversion of CO2 to CH4. Both the activity and selectivity of CH4 products over the pristine CuInSnS4 nanocrystal can be further improved by the modification of with various co-catalysts to enhance the separation of the photogenerated charge carrier. This work provides a non-metal active site to determine the conversion and selectivity of photocatalytic CO2 reduction.

High Oxygen Sensitivity of TiO2 Thin Films Deposited by ALD.

The gas sensitivity and structural properties of TiO2 thin films deposited by plasma-enhanced atomic layer deposition (ALD) were examined in detail. The TiO2 thin films are deposited using Tetrakis(dimethylamido)titanium(IV) and oxygen plasma at 300 °C on SiO2 substrates followed by annealing at temperatures of 800 °C. Gas sensitivity under exposure to O2 within the temperature range from 30 °C to 700 °C was studied. The ALD-deposited TiO2 thin films demonstrated high responses to O2 in the dynamic range from 0.1 to 100 vol. % and low concentrations of H2, NO2. The ALD deposition allowed the enhancement of sensitivity of TiO2 thin films to gases. The greatest response of TiO2 thin films to O2 was observed at a temperature of 500 °C and was 41.5 arb. un. under exposure to 10 vol. % of O2. The responses of TiO2 thin films to 0.1 vol. % of H2 and 7 × 10-4 vol. % of NO2 at a temperature of 500 °C were 10.49 arb. un. and 10.79 arb. un., correspondingly. The resistance of the films increased due to the chemisorption of oxygen molecules on their surface that decreased the thickness of the conduction channel between the metal contacts. It was suggested that there are two types of adsorption centers on the TiO2 thin films surface: oxygen is chemisorbed in the form of O2- on the first one and O- on the second one.

Novel Silicon-based schiff-base as corrosion inhibitor for anti-corrosion behavior of API 5L Grade B in 1M HCl

The efficiency inhibition of the novel Schiff-base compound named o-(2-(12-(2-((((E)-(5- (hydroxymethyl)furan-2-yl)methylene)carbamothioyl)oxy)ethyl)-1,7,9,15-tetraoxa-4,12-diaza-8- silaspipiro[7.7]pentadecan-4-yl)ethyl)(5-(hydroxymethyl)furan-2-yl)methylene)carbamothioate, for corrosion of API 5L B in aqueous media of 1 M HCl was assessed. The synthesized compound was characterized by 1H NMR, 13C NMR and FT-IR spectroscopy. Using electrochemical impedance espectroscopy, potentiodynamic polarization, atomic force microscopy, scanning electron microscopy and quantum chemical measurements, the behavior and corrosion protection mechanism of carbon steel was studied under the mentioned conditions. The optimizations of the geometry, was conducted utilizing the density functional theory methods. Measurements of potentiodynamic polarization showed the action of the intended inhibitor as a mixed inhibitor in the acid solution. As shown by the electrochemical impedance results, the charge transfer resistance was elevated and the double layer capacity showed a reduction by adding the inhibitor. According to the study of adsorption isotherms, the inhibitor adsorption in the solution on the steel surface matching with the Langmuir adsorption isotherm. The adsorption was a spontaneous process and the amount of the adsorption free energy reflected the chemical and physical occurrence of adsorption. Using atomic force microscopy and scanning electron microscopy investigations, the result of electrochemical methods was confirmed. The Monte Carlo and Molecular Dynamics simulation proved the flat adsorption of the inhibitor just on one side of the molecule, leading to exposing its adsorption centers to the steel surface. They were rather high, and it was in agreement with the experimental data acquired to date.