Transport Of Reagents Research Articles

Decoupling Fluorous Protein Coatings Yield Heat-Stable and Intrinsically Sterile Bioformulations.

Thermal inactivation is a major bottleneck to the scalable production, storage, and transportation of protein-based reagents and therapies. Failures in temperature control both compromise protein bioactivity and increase the risk of microorganismal contamination. Herein, we report the rational design of fluorochemical additives that promiscuously bind to and coat the surfaces of proteins to enable their stable dispersion within fluorous solvents. By replacing traditional aqueous liquids with fluorinated media, this strategy conformationally rigidifies proteins to preserve their structure and function at extreme temperatures (≥90 °C). We show that fluorous protein formulations resist contamination by bacterial, fungal, and viral pathogens, which require aqueous environments for survival, and display equivalent serum bioavailability to standard saline samples in animal models. Importantly, by designing dispersants that decouple from the protein surface in physiologic solutions, we deliver a fluorochemical formulation that does not alter the pharmacologic function or safety profile of the functionalized protein in vivo. As a result, this nonaqueous protein storage paradigm is poised to open technological opportunities in the design of shelf-stable protein reagents and biopharmaceuticals.

Measurement System Analysis of Densometry Technique for the Determination of Porosity and Thickness of Porous Fuel Cell Media

Porosity is one of the critical parameters governing mass transport of reagents and products in the heterogenous architecture of a fuel cell electrode. Techniques for the measurement thereof are required that are rapid, cost-effective, and simple, and yet capable of the highest levels of accuracy, precision, and stability. This body of work presents a comprehensive account of the measurement system analysis (MSA) of the densometer technique for the ex situ determination of total porosity and mean thickness of thin film porous materials by way of hydrostatic principles. The MSA involved a four phased approach which systematically tested several process assumptions before performing gage precision and accuracy studies and, finally, benchmarking of the system against several conventional industry techniques. Results confirmed statistically that the densometry technique, in conjunction with a standardized measurement procedure, can be used for the precise and accurate measurement of porosity as well as thickness across a representative range for porous materials deployed in fuel cells and similar technologies.

Managing the remediation strategy of contaminated megasites using field-scale calibration of geo-electrical imaging with chemical monitoring

Groundwater contamination is a threat to drinking water resources and ecosystems. Remediation by injection of chemical reagents into the aquifer may be preferred to excavation to reduce cost and environmental footprint. Yet, successful remediation requires complete contact between contamination and reagents. Subsurface heterogeneities are often responsible for diffusion into low-permeable zones, which may inhibit this contact. Monitoring the spatial distribution of injected reagents over time is crucial to achieve complete interaction. Source zone contamination at megasites is particularly challenging to remediate and monitor due to the massive scale and mixture of contaminants. Source zone remediation at Kærgård Plantation megasite (Denmark) is monitored here, with a new methodology, using high-resolution cross-borehole electrical resistivity tomography (XB-ERT) imaging calibrated by chemical analyses on groundwater samples. At this site, high levels of toxic non-aqueous phase liquids (NAPL) are targeted by in-situ chemical oxidation using activated persulfate. It may take numerous injection points with extensive injection campaigns to distribute reagents, which requires an understanding of how reagent may transport within the aquifer. A geophysical (XB-ERT) monitoring network of unprecedented size was installed to identify untreated zones and help manage the remediation strategy. The combination of spatially continuous geophysical information with discrete but precise chemical information, allowed detailed monitoring of sulfate distribution, produced during persulfate activation. Untreated zones identified in the first remediation campaign were resolved in the second campaign. The monitoring allowed adjusting the number of injection screens and the injection strategy from one campaign to the next, which resulted in better persulfate distribution and contaminant degradation in the second campaign. Furthermore, geophysical transects repeated over the timespan of a remediation campaign allowed high-resolution time-lapse imaging of reagent transport, which could in the future improve the predictability of transport models, compared to only using on a-priori assumptions of the hydraulic conductivity field.

Enhancing predictions of remedial reagent transport via a vertical groundwater circulation well with high-resolution aquifer characterization

The vertical groundwater circulation well (GCW) is a commonly used technique in contaminated sites to remove secondary contaminants from low permeable zones. Early GCW studies often used simple subsurface hydraulic properties, such as anisotropic homogeneous aquifers or low conductivity lens/blocks, to mimic the complex subsurface heterogeneity. Although studies based on simplified representations of aquifer heterogeneity provide straightforward flow and transport information for engineering design of a GCW, they may over- or under-estimate contaminant fate and transport in the field. The objective of this study is to identify key heterogeneity factors that control the capture zone extension and to examine the extent to which the accuracy of estimated heterogeneity spatial distributions influences the prediction of remedial reagent transport. To achieve these objectives, we utilized Monte Carlo simulation to investigate the extension of the circulation zone in heterogeneous aquifers and to identify the key factors that contribute most to the variability of the circulation zone. Three commonly used geostatistical approaches (equivalent homogeneous, kriging, and highly parameterized methods) were employed to estimate the spatial distributions of key factors. The reliabilities of these estimated fields were evaluated through their remedial reagent transport predictability. The key factor analysis revealed that the mean porosity value, the variance of lnK, and the correlation length of lnK profoundly influence the lateral expansion of the capture zone. Neglecting the aquifer hydraulic conductivity heterogeneity underestimates the extension of the circulation zone and the spread of remedial reagent. Additionally, utilizing a highly parameterized approach to estimate the high-resolution K field can accurately reproduce the key remedial reagent distributions. The concentration arrival time and peak concentration are significantly improved compared to those predictions based on the equivalent homogeneous and kriged K fields.

Electrostatic catalysis of a click reaction in a microfluidic cell

Electric fields have been highlighted as a smart reagent in nature’s enzymatic machinery, as they can directly trigger or accelerate chemical processes with stereo- and regio-specificity. In enzymatic catalysis, controlled mass transport of chemical species is also key in facilitating the availability of reactants in the active reaction site. However, recent progress in developing a clean catalysis that profits from oriented electric fields is limited to theoretical and experimental studies at the single molecule level, where both the control over mass transport and scalability cannot be tested. Here, we quantify the electrostatic catalysis of a prototypical Huisgen cycloaddition in a large-area electrode surface and directly compare its performance to the conventional Cu(I) catalysis. Our custom-built microfluidic cell enhances reagent transport towards the electrified reactive interface. This continuous-flow microfluidic electrostatic reactor is an example of an electric-field driven platform where clean large-scale electrostatic catalytic processes can be efficiently implemented and regulated.

In-situ oxygen generation using Titanium foam/IrO2 electrode for efficient sulfide control in sewers

Hydrogen sulfide (H2S) causes corrosion of pipeline network and endangers sewer’s normal operation, while the rehabilitation or replacement of sewer network incurs expensive manpower and material costs. Conventional chemical dosing strategies such as oxygen injection and caustic soda addition, confront issues with transport and storage of chemical reagents as well as dose control. In contrast, electrochemical treatment techniques have evoked growing attention in sewer management due to its capacity of in-situ effective agent production, real-time dose control and amenability to automation. In this study, the performances of anodic oxygen production using Ti/IrO2 and Titanium foam/IrO2 as electrodes were investigated. Titanium foam/IrO2 electrode exhibited the superior oxygen evolution capacity, with the dissolved oxygen (DO) level attained in the range 8–9 mg L-1 (i.e., higher than that of 5–6 mg L-1 by Ti/IrO2 electrode). It was also indicated that a decrease in flow rate or an increase in current density would accelerate its in-situ oxygen production. DO production with the presence of COD, NH4+, HCO3−, H2PO4−/HPO42− was approximately 6.78–8.37 mg L-1. Moreover, this electrochemical method was illustrated to successfully achieve sulfide removal efficiency of 90 % in the simulated sewage experiment. The cathode compartment simultaneously produced caustic soda (∼0.4 wt% in 210 min), thereby contributing to further sulfide removal. Additionally, the effect of real sewage with different conductivities on sulfide removal proved the wide applicability of electrochemical technology in sewer management. Overall, this study demonstrated the practical potential of concurrent in-situ anodic oxygen production and cathodic caustic soda generation for sulfide control in sewers.

Tailored Porous Carbon Xerogels for Fe-N-C Catalysts in Proton Exchange Membrane Fuel Cells.

Atomically dispersed Fe-N-C catalysts for the oxygen reduction reaction (ORR) have been synthesized with a template-free method using carbon xerogels (CXG) as a porous matrix. The porosity of the CXGs is easily tunable through slight variations in the synthesis procedure. In this work, CXGs are prepared by formaldehyde and resorcinol polymerization, modifying the pH during the process. Materials with a broad range of porous structures are obtained: from non-porous to micro-/meso-/macroporous materials. The porous properties of CXG have a direct effect on Fe-N-CXG activity against ORR in an acidic medium (0.5 M H2SO4). Macropores and wide mesopores are vital to favor the mass transport of reagents to the active sites available in the micropores, while narrower mesopores can generate additional tortuosity. The role of microporosity is investigated by comparing two Fe-N-C catalysts using the same CXG as the matrix but following a different Fe and N doping procedure. In one case, the carbonization of CXG occurs rapidly and simultaneously with Fe and N doping, whereas in the other case it proceeds slowly, under controlled conditions and before the doping process, resulting in the formation of more micropores and active sites and achieving higher activity in a three-electrode cell and a better durability during fuel cell measurements. This work proves the feasibility of the template-free method using CXG as a carbon matrix for Fe-N-C catalysts, with the novelty of the controlled porous properties of the carbon material and its effect on the catalytic activity of the Fe-N-C catalyst. Moreover, the results obtained highlight the importance of the carbon matrix's porous structure in influencing the activity of Fe-N-C catalysts against ORR.

Bioinspired Self‐Propelled Micromotors with Improved Transport Efficiency in the Subsurface Environment for Soil Decontamination

AbstractLimited transport efficiency of remediation reagents in the subsurface environment is regarded as a key challenge facing in situ soil remediation. Herein, taking advantage of natural hollow fibers, tubular micromotors capable of autonomous movement to facilitate the migration of remediation reagents and achieve efficient degradation of organic pollutants in soil are developed. Widely‐used nanocatalysts in soil treatment, Fe3O4 and MnO2, are integrated on the fiber surface to enable self‐propulsion via recoil of micro/nanobubbles and activation of hydrogen peroxide (H2O2) and peroxymonosulfate. Featured with tiny sizes and wireless motion, the micromotors navigate in microchannels and microenvironments with complex terrain. The dependence of transport efficiency in heterogeneous and porous environments on H2O2 concentration is revealed based on column studies. With fluorescent g‐C3N4 decorated on the surface to enable visualization, the horizontal/vertical migration of prepared micromotors in soil is proved to be greatly enhanced due to self‐propulsion and bubble generation. The micromotors exhibit excellent catalytic performances toward the degradation of a wide spectrum of water‐soluble antibiotics and water‐insoluble polycyclic aromatic hydrocarbons. Overall, the bioinspired micromotors unveil a new strategy to improve the transport of remediation reagents in the subsurface environment, which holds great potential for efficient in situ soil treatment.

Enzymatic and catalytic behaviour of low-dimensional gold nanomaterials in modular nano-composite hydrogels

Inorganic nanoparticles have long been applied as catalysts and nanozymes with exceptional rate constants arising from their large surface areas. While it is understood that high surface area-to-volume ratios and low average atomic coordination are responsible for their exceptional catalytic properties, these facets remain under exploited in the design of gold nanoparticle catalysts and nanozymes. Here we have developed 3D, 2D, and quasi-1D gold nanoparticles for use as catalysts in reducing 4-nitrophenol by sodium borohydride. Each morphology was characterised with transmission electron microscopy and UV–vis absorption spectroscopy, while the highest catalytic activity was achieved when the perimeter-to-surface area, or amount of ‘edge’, was maximised. The particles were then applied as nanozymes in modular nano-composite hydrogels. Independent hydrogel tiles containing either the substrate or catalyst were bonded in stacks, which allowed reagent transport across their interface for the colourimetric detection of hydrogen peroxide. This work presents novel insight into the catalytic activity of low-dimension nanoparticles and their potential application in nanozyme-based diagnostic devices.

Self-propelled micromotors based on natural pyrolusite for dynamic remediation of organic contaminated soil

For in situ chemical oxidation (ISCO) technologies in soil remediation, one of the key challenges is the limited diffusion range of chemical oxidants in soil without external agitation. Herein, self-propelled micromotors based on natural pyrolusite with abundant micro/nanobubble generation were developed as active heterogeneous catalysts to improve the mass transport of remediation reagents. The micromotors composed of natural pyrolusite and Fe2O3 were employed as activators of peroxymonosulfate (PMS) and hydrogen peroxide (H2O2) for dynamic remediation of soil contaminated by polycyclic aromatic hydrocarbons (PAHs). The prepared micromotors exhibited speeds of 185 ± 33.7 µm/s, 280 ± 53.9 µm/s and 312 ± 66.2 µm/s in 1 %, 3 % and 5 % H2O2, respectively. The dual effect of NPF micromotors in catalytic degradation and mass transport led to a pyrene degradation efficiency of 100 % in 5 h and a total organic content removal rate of 93.36 % in the reaction condition of 1.0 g/L of NPF, 20 mM of PMS, 20 mM of H2O2, 84.10 mg/kg of pyrene and natural pH. Meanwhile, the main reactive oxidant species (ROS) and degradation pathway of pyrene were investigated. This research demonstrates the high potential of natural-pyrolusite-based micromotors for in situ remediation of organic contaminated sites.

Performance improvement of lateral flow assay using heterogeneous nitrocellulose membrane with nonuniform pore size

Lateral flow assay (LFA) has found widespread applications in point-of-care diagnostics over the past decades. Its detection sensitivity is dependent on the properties of paper itself (e.g., porous microstructure of nitrocellulose membrane), however, the effect remains unknown. Existing mathematical models for LFA have not been proved to predict the variation trends of detection performance with different specifications of nitrocellulose membrane. To address this, we developed a mathematical model coupling the macroscopic capillary flow and the binding reaction on the internal pore surface to illustrate the complex interaction among the convection, diffusion, and binding reaction with different nitrocellulose membranes. The model was experimentally validated by implementing nucleic acid detection on LFA. The simulated results suggest that due to the trade-off between the reagent transport and the reactive surface area, there is an optimal average pore size of the nitrocellulose membrane to achieve the highest detection sensitivity. Additionally, a heterogeneous pore distribution design (i.e., smaller pore diameter at the test line region and larger pore diameter for the rest region) of the nitrocellulose membrane was proposed to provide a faster detection with improved sensitivity. The numerical model would be a practical tool for the material selection and optimization of LFA.

Portable rapid detection of maize chlorotic mottle virus using RT-RAA/CRISPR-Cas12a based lateral flow assay.

Maize lethal necrosis seriously threatens maize production worldwide, which was caused by coinfection by maize chlorotic mottle virus (MCMV) and a potyvirid. To effectively control maize lethal necrosis, it is vital to develop a rapid, sensitive, and specific detection method for the early diagnosis of MCMV in host plant tissues. We established a rapid detection procedure by combining the one-step reverse-transcription recombinase-aided amplification (one-step RT-RAA) and CRISPR/Cas12a-based lateral flow assay in one tube (one-tube one-step RT-RAA/CRISPR-Cas12a), which can be implemented on a portable metal incubator at 37~42°C. Furthermore, the crude extract of total RNA from plant materials using alkaline-PEG buffer can be directly used as the template for one-step RT-RAA. The developed one-tube one-step RT-RAA/CRISPR-Cas12a lateral flow assay can detect as low as 2.5 copies of the coat protein (CP) gene of MCMV and 0.96 pg of the total RNA extracted from MCMV infected maize leaves. Furthermore, the MCMV infected maize leaves at 5 dpi having no obvious symptoms was detected as weak positive. The crude extraction method of total RNA from plant materials required no complicated device, and all the procedures could be implemented at room temperature and on a portable metal incubator, costing a total time of about 1h. The one-step RT-RAA reagents and CRISPR/Cas12a reagents can be lyophilized for easy storage and transportation of reagents, which makes this method more feasible for the filed detection. This method presents rapidness, robustness and on-site features in detecting viral RNA, and is a promising tool for the field application in minimally equipped laboratories.

Automated cellular stimulation with integrated pneumatic valves and fluidic capacitors.

Microfluidic technologies have proven to be a reliable tool in profiling dynamic insulin secretion from islets of Langerhans. Most of these systems rely on external pressure sources to induce flow, leading to difficulties moving to more elaborate systems. To reduce complexity, a microfluidic system was developed that used a single vacuum source at the outlet to drive fluidic transport of immunoassay reagents and stimulation solutions throughout the device. A downside to this approach is the lack of flow control over the reagents delivered to the islet chamber. To address this challenge, 4-layer pneumatic valves were integrated into the perfusion lines to automate and control the delivery of stimulants; however, it was found that as the valves closed, spikes in the flow would lead to abnormal insulin secretion profiles. Fluidic capacitors were then incorporated after the valves and found to remove the spikes. The combination of the valves and capacitors resulted in automated collection of insulin secretion profiles from single murine islets that were similar to those previously reported in the literature. In the future, these integrated fluidic components may enable more complex channel designs to be used with a relatively simple flow control solution.

The role of iron-bearing minerals for the deep weathering of a hydrothermally altered plutonic rock in semi-arid climate (Chilean Coastal Cordillera)

Weathering is a fundamental process that controls the development of Earth's surface by the formation of erodible material and the release of mineral-bound nutrients. Weathering at depth has been predominantly studied in humid environments, where fluid flow sets mineralogical transformations, whereas (semi-)arid regions were barely investigated in this respect. In many studies the weathering of iron-bearing minerals was shown to play a major role for the advance of weathering at depth. Weathering of iron-bearing minerals is often superimposed on factors that precondition rocks for weathering such as hydrothermal alteration and fracturing by tectonic stress. The low degree of water-rock interactions in (semi-)arid climates offers the opportunity to single out the preconditioning factors and explore the role of iron-bearing minerals for weathering in detail. To this end the interactions of tectonic fracturing, hydrothermal alteration and weathering were investigated in a deep, weakly weathered profile of plutonic rock in a semi-arid region (Santa Gracia, Northern Chile). The profile was recovered by an 87-m-deep drill core and a 2-m-deep soil pit which were used to investigate the mineral composition, magnetic susceptibility, geochemical gradients, and Fe redox-state.Non-cemented fractures of tectonic origin were identified as pathways for the transport of fluids and reagents to depth that are fuelling the initial weathering reactions. Previous hydrothermal fluids mainly migrated along the same fractures and altered the properties of the original bedrock. Therefore, the weathering features along fractures depend on the preconditioning by hydrothermal alteration and tectonic stress which affected the vicinity of these fractures. From the fracture surfaces, water and O2 diffuse into the rock and initiate oxidation and dissolution-reprecipitation reactions. Our study shows that the transformation of iron-bearing silicates (especially biotite) to Fe(III) (oxyhydr)oxides and clay minerals is the dominant weathering-promoting process as it produces stress which leads to micro-fracturing of the rock and finally to the formation of saprolite.Deciphering the links between tectonic fracturing, hydrothermal alteration, and weathering-induced fracturing by iron-bearing silicates in semi-arid settings provides unique insights into the controls of deep weathering in regions with limited fluid flow.

Comparison of the sensitivity, specificity, correlation and inter-assay agreement of eight diagnostic in vitro assays for the detection of African swine fever virus.

With the recent spread of African swine fever (ASF) in Europe, Asia and the Caribbean region, after being endemic for decades in Africa, PCR-based commercial kits and various master mixes are increasingly being used in addition to the Office International des Epizooties-recommended protocol from King etal. (World Organization for Animal Health). Often, the availability and cost of commercial kits or master mixes can be a limiting factor for diagnostic laboratories, in addition to the requirements for transportation and storage of temperature-sensitive reagents in remote areas. In such cases, alternatives should be ready to maximize surveillance and mining of ASF. To evaluate alternatives, we tested five commercial quantitative real-time PCR (qPCR) master mixes from Applied Biosystems, Bio-Rad, Biotechrabbit, Promega and Qiagen using the same primers and probe mix derived from the King etal.'s protocol for the sensitivity, specificity, correlation and inter-assay agreement. We further included three ad hoc molecular diagnostic kits (VetMax™ African Swine Fever Virus Detection Kit [Applied Biosystems], ID Gene African Swine Fever Duplex [ID-Vet] and Virotype ASF PCR Kit [Qiagen/Indical]). The limit of detection (LOD) was assessed for each assay. The comparative study panel comprised 83 archived DNA samples from ASF virus (ASFV) clinical samples, belonging to five different genotypes from outbreaks in 16 countries in Asia and Africa. The analytical specificity was assessed against a panel of swine pathogens. The LOD ranged from 13 to 41 gene copies per reaction; VetMax ™ African Swine Fever Virus Detection Kit from Applied Biosystems exhibited the lowest detection limit (13 gene copies per reaction) and iQ Supermix from Bio-Rad the highest detection limit (41 gene copies per reaction). Cq values obtained from the lowest dilution, in which all replicates (n=25) could still be amplified (50 gene copies per reaction), were not significantly different between kits using Kruskal-Wallis test. Inter-assay agreement was assessed using statistical test Fleiss-Kappa and was shown to be excellent in all cases. Agreement using statistical test Bland-Altman was good for samples with Cq values<25 and moderate for Cq values>25. We conclude that all the assays evaluated in this study can be used for the routine detection of ASFV.

How Catalyst Dispersion Solvents Affect CO2 Electrolyzer Gas Diffusion Electrodes

Cathode gas diffusion electrodes (GDEs) in CO2 electrolyzers facilitate reagent transport and the reduction of CO2 into chemicals and fuels. While GDEs are routinely leveraged to achieve high rates of product formation, design principles for high-performing cathodes have not yet been established. In this report, we demonstrate the influence of a central parameter in GDE fabrication, the catalyst ink solvent, on the properties and performance of spray-coated cathode GDEs. We show that the choice of solvent used during catalyst deposition impacts the faradaic efficiency for CO by as much as 50% at 200 mA cm–2. Moreover, the solvent modulates the surface area, hydrophobicity, and capillarity of GDE catalyst layers. By measuring the hydrodynamic radii of catalyst inks, we conclude that solvent-mediated ionomer aggregation is a key factor that affects the microstructure and properties of GDE catalyst layers. We find that using ethanol as the ink solvent promotes moderate ionomer aggregation and yields the highest performing GDEs. This work describes the influence of electrode fabrication methodologies and demonstrates practical methods for preparing GDEs.

Boron-Rich Boron Carbide Nanoparticles as a Carrier in Boron Neutron Capture Therapy: Their Influence on Tumor and Immune Phagocytic Cells.

The aim of the work was to study the interaction between boron-rich boron carbide nanoparticles and selected tumor and immune phagocytic cells. Experiments were performed to investigate the feasibility of the application of boron carbide nanoparticles as a boron carrier in boron neutron capture therapy. Boron carbide powder was prepared by the direct reaction between boron and soot using the transport of reagents through the gas phase. The powder was ground, and a population of nanoparticles with an average particle size about 80 nm was selected by centrifugation. The aqueous suspension of the nanoparticles was functionalized with human immunoglobulins or FITC-labeled human immunoglobulins and was then added to the MC38 murine colon carcinoma and to the RAW 264.7 cell line of mouse macrophages. Flow cytometry analysis was used to determine interactions between the functionalized boron carbide nanoparticles and respective cells. It was shown that B4C–IgG nanoconjugates may bind to phagocytic cells to be internalized by them, at least partially, whereas such nanoconjugates can only slightly interact with molecules on the cancer cells’ surface.

Preparation of Catalyst from Phosphorous Rock Using an Improved Wet Process for Transesterification Reaction

Gypsum (CaSO4·2H2O) with active catalytic performance was prepared from phosphorous rock through an improved clean wet process. The impact of the preparation conditions was extensively analyzed to identify the statistical significance toward the compositions of the prepared gypsum and catalytic performances during the transesterification reaction. The prepared catalyst predominantly contains CaSO4 (93%) with contaminations of silica (5%), P2O5 (0.25%), Fe2O3 (0.52%), Al2O3 (0.24%), and TiO2 (0.12%). Heavy-metal oxides, that is, Cr2O3, PbO, and CuO, were not detected from the prepared catalyst. The contaminants in gypsum are in the form of complicated composites such as SiO2, (Na2, K2)SiF6, MgF2, AlF3, Ca5(PO4)3F, and Ca3(PO4)2. The significant operational parameters, namely, the crystallization temperature and duration toward the catalytic performance, were identified by ANOVA. The Brönsted acidic sites from the ionic S and O, which might be in the form of S–⃛O or S═O as the surface functional groups, attribute to transesterification catalysis. The theoretical simulation suggests that different ionic sulfates might co-exist on the surface of crystallite gypsum. The transport of reagents to the surface of catalytic sites also plays an important role under the investigated experimental conditions. The reusability study indicates an approximate 10% deactivation after the reaction.

Catalytic conversion of glucose into sorbitol over niobium oxide supported Ru catalysts

Abstract Sorbitol is a sugar alcohol of great importance in cosmetic, food and pharmaceutical industry as well as the production of biopolymers. This work aimed at the synthesis of sorbitol from the hydrogenation of glucose using Ru/Nb2O5 catalysts in the amorphous and crystalline phases. The catalysts were synthesized from the wet impregnation method and characterized by N2 adsorption isotherms, TGA/DTG, EDXRF, XRD, TPR-H2, XPS and SEM. The catalytic tests presented results of high conversion rates of glucose reaching 85 % and 99 % of selectivity to sorbitol when using Nb2O5 in the crystalline form as support, and 53 % and 55 % in the conversion and selectivity, respectively, when the amorphous phase of Nb2O5 was used as support. The structural modification of the catalytic support positively favored the catalyst activity and sorbitol production, allowing the formation of nanometric particles of the active metal on the surface alongside the increase of the mesoporosity, thereby facilitating the transport of reagents.

(Keynote) Gaining Control over the Morphology of Metal–Organic Frameworks

Owing to their vast ratio of surface area to mass and volume, metal-organic frameworks (MOFs) revolutionized many applications that rely on chemical and physical interactions at surfaces. However, a great challenge today is to build MOF materials that translate the functionality at the molecular level effectively to the macroscopic world. To do this, effective transport of reagents to, from, and within MOF materials is critical. To overcome this barrier, porous materials will need to be structured with feature sizes from below one micrometre to the millimetre or centimetre scale. In fact, the challenge of morphology control over multiple length scales of MOF materials is overlooked by researchers so far but is the key to enable groundbreaking real-world applications.The synthesis of a MOF material always starts with the strategic selection of precursor materials. Besides an organic building block, an inorganic compound providing metal ions is necessary, which most commonly is a metal salt, as it easily dissolves. A relatively new and different approach is the use of metal oxides (MOs). Even though their use is challenging due to low solubility issues and slow and non-homogenous conversion, by carefully optimizing the experimental conditions the MO–to–MOF conversion can be carried out with preserving the morphology of the MO (Figure 1). Thus, the use of MO precursors, which offers a huge number of different morphologies that can be synthesized with high precision, potentially provides an easy and smart way for the precise synthesis of different MOF morphologies. This strategy opens the door to morphologies that cannot be achieved using reactions based on metal salt precursors or other approaches.This contribution focuses on (1) the study of different MOs as precursors for MOF formation, (2) giving a deep insight in the underlying chemistry, and (3) application of this knowledge to convert different complex 3D morphologies of MOs into MOFs. Our findings demonstrate that all MOs tested so far can be used as precursors for the synthesis of MOFs, although they not always preserve the parent shape. To illustrate the capacity of the SP approach and to uncover the full mechanistic details of the early stages of this process we explored the conversion of ZnO into the zeolitic imidazolate framework (ZIF) ZIF-8 in detail. ZIFs are a group of MOFs that are structurally very similar to the well-known zeolites. Zeolites are composed of [TO4] (T = Si, Al) tetrahedrons covalently joined by bridging oxygen atoms and ZIFs of [MN4] (M = transition metal ion) tetrahedrons with bridging five-membered imidazolate units with very similar bridging angles and framework topologies. Finally, we used the gained knowledge to convert different three dimensional 3D ZnO morphologies into ZIFs.Figure: Conversion of metal oxides (MOs) into metal—organic frameworks (MOFs) with the competing rates k1 (MO dissolution), k2 (diffusion), k3 (MOF nucleation), and k4 (MOF growth). Certain conditions of the reaction medium lead to MO dissolution, followed by diffusion of metal ions and organic linkers. Depending on the ratios of the different rates either homogeneous nucleation within the solution or heterogeneous nucleation on the MO-medium interface occurs (or a mixture of both). The former can be understood as a dissolution-crystallization (DC) mechanism, analogous to reactions using metal salt precursors, the latter as a shape-preservation (SP) mechanism. Figure 1