Siliceous Mesocellular Foam Research Articles

Siliceous mesocellular foam supported Cu catalysts for promoting non-thermal plasma activated CO2 hydrogenation toward methanol synthesis

Siliceous mesocellular foam supported Cu catalysts for promoting non-thermal plasma activated CO2 hydrogenation toward methanol synthesis

High-efficiency selective enrichment of U(VI) from aqueous solutions by amidoxime-functionalized siliceous mesocellular foams

Siliceous mesocellular foams (MCFs) with high surface area, large pore volume and ordered mesoporous structure have a great potential in the capture of pollutants. To achieve the sorption of U(VI) with enhanced capacity and selectivity, amidoxime groups were modified on MCFs by optimizing the molar ratio of (2-cyanoethyl) triethoxysilane (CPTES) in silicon source from 0% to 30%. CPTES promoted the grafted amounts of amidoxime group (0–1.85 mmol/g) while resulted in the collapse of mesopores of amidoximated MCFs from 426.5 to 136.3 m2/g. Sorption behaviors of U(VI) at the interface of amidoximated MCFs and solutions were systematically investigated under various hydrochemical conditions. Amidoximated MCFs could capture U(VI) rapidly (4.0 h) with superior maximum sorption capacity (446.6 mg/g at pH 5.0 and T 298 K), and favorable reusability (67.8% of capacity remained after six recycles). Selective enrichment of U(VI) from artificial nuclide wastewater (201.5 mg/g of capacity, 16.08–33.61 of selectivity coefficients) and seawater (179.3 mg/g of capacity, 5.08–20.48 of selectivity coefficients) against the interference of heavy metals and nuclides were presented. This study provided a valuable reference for the preparation of sorbents with surface amidoximation and advanced porosity as well as a meaning option for the extraction of nuclides from aqueous solutions.

Renewable Hydrogen Production with Steam Reforming of Ethanol Using Siliceous Mesocellular Foam‐Supported Nickel Catalysts

Nickel (Ni) catalysts loaded on siliceous mesocellular foam (MCF‐S) are synthesized via the wet impregnation method with 3, 5, 10, and 15 wt% NiO loadings and different aging levels (no, partial, and full ageing) to determine how both factors affect the progress of the ethanol steam reforming (ESR) reaction. After extensive material characterization testing to determine material porosity, crystallinity, and Ni metal particle size and spatial location, as well as reaction testing at 300–700 °C and 4 H2O: 1 EtOH molar ratio, the fully aged 10 wt% Ni/MCF‐S possesses the strongest structural stability and catalytic activity, reaching 100% EtOH conversion and 68% H2 selectivity at 700 °C. The aging disperses and embeds more Ni nanoparticles within the walls of the mesopores, which promote the ESR reaction from easier diffusion and more active site contact within the pores. Furthermore, the catalyst reveals little signs of deactivation, as the structure remains virtually unchanged, and any coke formed is on the silica support and not over the Ni nanoparticles after the ESR reaction. Such results have demonstrated a proven applicability for ESR and a further need to research about aging effects toward improving structural properties and the catalytic reaction activity.

Fabrication of hyperbranched polyamidoamine immobilized mesocellular siliceous foam for rapid decontamination of lead(II) from aqueous solution

Developing of adsorbents with merits of higher adsorption capacity and quicker adsorption equilibrium through facile method merits more attention. Generally, large specific surface area porous adsorbent coupled with multi functional groups is a wise option. In the current work, a feasible protocol of preparing efficient adsorbent toward Pb2+ was established via integrating amino abundant hyperbranched polyamidoamine and bimodal pore structured mesocellular siliceous foam. The polyamidoamine was synthesized through a vacuum thermo polymerization method by gradually elevating temperature. The uniform spherical mesocellular siliceous foam substrate was prepared via inorganic salt-assisted soft-template method, and the pore structure and particle morphology were adjusted through post hydrothermal treatment. The obtained hyperbranched polyamidoamine immobilized mesocellular siliceous foam was characterized using FT-IR, SAXS, BET, SEM, TEM, TGA and zeta potential measurement techniques. Large specific surface area, unique bimodal pore structure with interconnected spherical and window pore and ultra large pore diameter rendered the adsorbent high adsorption capacity and efficient elimination. Batch experiment results elucidated that various operating parameters including pH, contact time, initial Pb2+ concentration, temperature and ionic strength deemed to be at play in adsorption behavior. The measured experimental maximum adsorption capacity at 298.15 K was 142.87 mg·g−1. The equilibrium data fitted well by pseudo second order kinetic model unveiled that the rate determining step might be chemical adsorption. The adsorption behavior was found to more suitable described with Langmuir isotherm model, implying the formation of adsorbate monolayer, and thus a maximum adsorption capacity of 315.46 mg·g−1 at 298.15 K was estimated. An underlying spontaneous entropy increased endothermic nature of adsorption of Pb2+ by the as-prepared adsorbent was conceived through adsorption thermodynamics study. Furthermore, a possible adsorption mechanism of comprehensive interaction of chemical chelation and ion exchange was proposed. This study supports the prospect that hyperbranched polyamidoamine immobilized mesocellular siliceous foam can serve as a candidate for efficiently removing Pb2+ from aqueous solution.

CO2 capture from dilute sources using triamine functionalized MCF silica at ambient temperature

A series of mesocellular siliceous foams (MCFs) with three-dimensional (3D) interconnected porous structure and tunable porosity were synthesized as supports to prepare triamine grafted sorbents using N’-[2-(3-trimethoxysilylpropylamino)ethyl]ethane-1,2-diamine for CO2 capture, particularly focusing upon the impact of pore structure of support on the adsorptive properties of final sorbents. The results indicate that both pore volume and diameter of MCF played a critical role in both CO2 adsorption capacity and kinetics at ambient temperature. Tested at 25 °C, the sorbent prepared by MCF with a large pore size of 33.7 nm and pore volume of 3.24 cm3/g exhibited remarkable CO2 adsorption capacity at low CO2 concentrations, which could achieve 2.14 mmol/g at 0.15 bar CO2 and 1.34 mmol/g under simulated air of 500 ppm CO2. Advanced characterization demonstrated that the increasing pore volume and diameter led to an increase of amine density on the MCF surface, which could enhance the steric hindrance and reduce the amine efficiency for CO2 adsorption at ambient temperature. It was also found that large pore size benefits the CO2 adsorption kinetics as the t80 and t90 of sorbents decreased with an increasing pore size of support. Moreover, the MCF-based sorbents exhibited superior thermo-stability with no adsorption loss during 50 cyclic adsorption-desorption tests. These results highlighted that the 3D MCF is a promising material for preparing amine grafted sorbents for flue gas CO2 capture and air purification applications.

Unravelling the real active center for CO oxidation-Cu+ or Cu3+: A case of model LaCuO3/MCF

Cu-based catalysts are one of the promising alternatives for industrial carbon monoxide (CO) oxidation applications. However, the exact active sites as well as their natures for CO oxidation have been still not fully understood yet. Herein, we designed and constructed a nano-size LaCuO3 perovskite oxide supported on inactive mesocellular siliceous foam (MCF), in which, the Cu species is featured by Cu3+. Then, LaCuO3-y/MCF with abundant Cu+ species was obtained by treating the as-prepared LaCuO3/MCF in H2/N2 flow. The catalytic activities of LaCuO3/MCF and LaCuO3-y/MCF were investigated for CO oxidation. The experimental results revealed that the Cu+ species rather than Cu3+ was the reactive site for CO oxidation. Moreover, density functional theory (DFT) calculations uncovered that the Cu+ species not only considerably facilitated the adsorption of CO and O2, but also dramatically reduced the desorption energy of CO2 from defective surface, thereby enhancing the catalytic activity of CO oxidation over Cu+ notably.

Turning CO2 to CH4 and CO over CeO2 and MCF-17 supported Pt, Ru and Rh nanoclusters – Influence of nanostructure morphology, supporting materials and operating conditions

Efficient conversion of CO2 into CH4 and CO brings an important opportunity to get valuable feedstock for a variety of industrially important reactions as both CH4 and CO are widely used as starting materials for the synthesis of valuable fuels and chemicals. Herein, we synthesized sub-nanometer (<2nm) Platinum (Pt), Ruthenium (Ru) and Rhodium (Rh) nanoclusters (NCs) via colloidal method; successfully decorated over mesoporous CeO2 and high surface area (HSA) siliceous meso-cellular foam (MCF 17) and tested for high-pressure CO2 reduction at lower temperature range (220–340 °C). Pt and Ru NCs exhibited typical reverse water gas shift (RWGS) and methanation catalytic performance respectively with minimal influence of the nature of support however, Rh NCs showed drastic variations in the product selectivity which exhibited strong influence of the support over the product distribution. Furthermore, Ru NCs (with a relatively lower metal loading ∼ 1 wt%) were found to be highly selective to CH4 (∼99 %) and stable (upto 40 hr time on stream) with either CeO2/MCF 17 at 340 °C; also Ru NCs exhibited comparatively the highest CO2 conversion (∼93 % in case of Ru NCs/CeO2) among the supported metal NCs. HRTEM results showed that metal NCs were homogeneously dispersed with a controlled and uniform particle size (<2nm); no substantial agglomeration of Ru NCs were observed after reaction. Beside the stable dispersion of NCs, Near Ambient Pressure (NAP) in situ XPS of Ru/CeO2 showed that the dynamic Ce3+/Ce4+ ratio of CeO2 can attribute to the high activity and selectivity.

Amine functionalized mesocellular silica foam as highly efficient sorbents for CO2 capture

A series of amine-functionalized CO2 sorbents were synthesized by grafting mono- and tri-amine substituted trialkoxysilanes on mesocellular siliceous foam (MCF) via a facile wet grafting method. The effect of amine type, amine loading level, and porous structure of silica on the CO2 adsorption performance was investigated. MCF silica with a three-dimensional (3D) interconnected porous structure was found to be suitable for preparing amine-grafted sorbents. Tested at 25 °C and 0.15 bar of CO2, the mono- and tri-amine grafted MCFs exhibited a fast adsorption rate and excellent CO2 adsorption capacity of 1.71 mmol/g for mono-amine and 2.07 mmol/g for tri-amine, which was much higher than amine grafted PQ and SBA-15 with a 2D porous structure, and the amine grafted silica sorbents prepared in previous studies. The large pore volume and pore size coupled with superior interconnectivity of MCF enable more surface silanol groups available and accessible for amino silanes, leading to a high amine loading level and excellent amine dispersion on the silica surface, which enhances both the CO2 adsorption capacity and adsorption rate of the developed sorbents. Cyclic adsorption–desorption tests confirmed the excellent stability of the amine grafted MCF.

Synthesis and characterization of immobilized glucoamylase on mesocellular foams through spectroscopic techniques and catalytic activity of immobilized enzyme

Siliceous mesocellular foam (MCF) is versatile support material for enzyme immobilization. This material is attractive for its robust, well-defined pore structure with interconnected, ultra large pores that facilitate diffusion. Excellent activity and extremely low level of leaching (metal or enzyme) were attained with these robust supports. MCF was synthesized by hydrothermal procedure using tetraethylorthosilicate (TEOS), amphiphilic block co-polymers Pluronic P123 and Trimethyl benzene as auxilary chemical under acidic conditions. The amino groups have been grafted to as-synthesized mesoporous silica by 3-aminopropyl trimethoxysilane (3-APTS) and glutaraldehyde was then coupled with amino functionalized silica. The physicochemical properties of the prepared materials were characterized by Nitrogen adsorption – desorption, FTIR, XPS, CPMAS NMR techniques. Meso cellular foams having ultra large pore diameter of 241 Å. Results showed that glutaraldehyde bound silica showed highest stability for enzyme binding.

Tungsten-doped siliceous mesocellular foams-supported platinum catalyst for glycerol hydrogenolysis to 1,3-propanediol

By varying the mass ratio of the swelling agent 1,3,5-trimethylbenzene (TMB) to the template P123 during the synthesis of the W-MCFs, we prepared a series of tungsten-doped siliceous mesocellular foams (W-MCFs) supported Pt catalysts (Pt/W-MCFs). In glycerol hydrogenolysis, the Pt/W-MCFs catalysts were highly active and selective to 1,3-propanediol (1,3-PDO), attributable to the 3-dimensional continuous large pore structure of the W-MCFs that facilitates the entry of the reactant and the escape of the product. Among the Pt/W-MCFs catalysts, the Pt/W-1.5MCFs catalyst with the TMB/P123 ratio of 1.5 exhibited the best activity and 1,3-PDO selectivity. Remarkably, the Pt/W-1.5MCFs catalyst afforded a high 1,3-PDO selectivity of 65 % at high glycerol conversion, thus rendering the highest 1,3-PDO yield of 63 %. The synergy between the Pt nanoparticles and the single-sited tetrahedral WVO4 species at the metal–oxide interface is proposed to be responsible for the differences in the catalytic performances among the Pt/W-MCFs catalysts.

Efficient Heterogeneous Palladium Catalysts in Oxidative Cascade Reactions.

ConspectusPalladium-catalyzed oxidations involving cascade processes provide a versatile platform for streamlined conversion of simple feedstocks into functional molecules with high atom and step economy. However, the achievement of high palladium efficiency and selectivity in Pd-catalyzed oxidative cascade reactions is still challenging in many cases, as a result of the aggregation of active palladium species to Pd black and the possible side reactions during each bond-forming step. The two current solutions for addressing these issues are either to utilize oxidant-stable ligands or to use electron transfer mediators (ETMs). The former solution, which includes the use of amines, pyridines, sulfoxides, and carbene derivatives, inhibits aggregation of Pd0 during the catalytic cycle, while the latter solution facilitates reoxidation of Pd0 to PdII to improve the activity and selectivity. Following our long-standing interest in Pd-catalyzed oxidations, very recently we developed heterogeneous catalysts to resolve the issues mentioned above in oxidative cascade reactions. The heterogeneous palladium catalysts (Pd-AmP-MCF or Pd-AmP-CNC) comprise palladium nanoclusters (1–2 nm) immobilized on amino-functionalized siliceous mesocellular foam (MCF) or on crystalline nanocellulose (CNC), exhibiting high activity, selectivity as well as excellent recycling ability.In this Account, we will discuss the synthesis and characterizations of the heterogeneous palladium catalysts, as well as their catalytic behaviors, and the mechanisms involved in their reactions. An important aspect of these catalysts in oxidation reactions is the generation of active Pd(II) species within the heterogeneous phase. Typical oxidative cascade reactions of our recent research on this topic include oxidative carbocyclization-carbonylation, oxidative carbocyclization-borylation, oxidative alkynylation-cyclization, oxidative carbonylation-cyclization, and oxidative carbocyclization-alkynylation. These reactions provide access to important compounds attractive in medicinal chemistry and functional materials, such as γ-lactone/γ-lactam-based poly rings, cyclobutenols, highly substituted furans, and oxaboroles. During these processes, the heterogeneous catalysts exhibited much higher turnover numbers (TONs) than their homogeneous counterparts (e.g., Pd(OAc)2) as well as unique selectivity that cannot be achieved by homogeneous palladium catalysts. The origin of the high efficiency and unique selectivity of the heterogeneous catalysts was also investigated. Asymmetric syntheses for the construction of optically pure compounds were realized based on the excellent selectivity in these heterogeneous processes. Kinetic studies revealed that the rate and yield of the reactions were essentially maintained during recycling, which demonstrates that Pd-AmP-MCF and Pd-AmP-CNC are robust and highly active in these oxidative cascade reactions. In addition, inductively coupled plasma optical emisson spectroscopy (ICP-OES) analysis and hot filtration test suggest that these processes most likely proceed via a heterogeneous pathway.Recent progress in our group has shown that the activity of Pd-AmP-MCF and Pd-AmP-CNC could be improved even further by the addition of Ag+ to generate cationic Pd(II). Furthermore, intriguing solvent effects were observed in a Pd-AmP-MCF-catalyzed oxidative cascade process, and solvent-controlled chemoselective transformations were developed based on this property of the catalyst. The heterogeneous strategy of this Account provides solutions to palladium deactivation and selectivity issues in Pd(II)-catalyzed oxidative cascade reactions and enables efficient catalyst recycling, which will open up new opportunities in oxidative cascade reactions.

Mixed-amine modified mesocellular siliceous foam: Improving the dispersity of polyethylenimine for CO2 adsorption

Mesocellular siliceous foams (MCFs) modified with three kinds of mixed-amines, polyethylenimine (PEI)/3-aminopropyltrimethoxysilane (APTMS), polyethylenimine/ diethylenetriamine (DETA) and polyethylenimine/tetraethylenepentamine (TEPA) are used to CO2 adsorption. The effect of the amount of amines and temperature are investigated in detail on CO2 adsorption capacity. The adsorption capacity of MCF modified by PEI-APTMS is 2.36 mmol/g at 75 °C when the content of APTMS is 20 wt%. For MCF modified by PEI-DETA, there is almost no promoting effect on the adsorption of CO2, which is largely due to the poor dispersibility of DETA to PEI. With the nitrogen content and long alkyl chain in TEPA, PEI-TEPA modified MCF has adsorption advantages under low temperature conditions. The adsorption capacity is increased by 76% at 30 °C when the outlet concentration of CO2 is 10%. In general, the adsorption capacities of mixed amines for CO2 are increased by the increase of adsorption rate and adsorption time.

Enhancement of Hydrothermal Stability and CO2 Adsorption of Mg-MOF-74/MCF Composites.

Hierarchical porous composite Mg-MOF-74/MCFs were successfully synthesized using a simple and facile method under in situ solvothermal conditions. Textural structures and morphologies of the composites were characterized by X-ray diffraction (XRD), N2 adsorption–desorption isotherms, and scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The results demonstrate that a large amount of nanosized Mg-MOF-74 particles is incorporated into the pores of mesocellular siliceous foams (MCFs) without remarkable aggregation and the composites possess microporous and mesoporous characteristics of both components. In addition, CO2 adsorption properties of the composites were tested in a fixed bed with/without hydrothermal treatment. The total CO2 adsorption capacities were calculated by breakthrough curves. The CO2 adsorption capacity of the composites reaches 1.68 mmol/g, which is smaller than that of pristine Mg-MOF-74. However, the total CO2 adsorption capacity of the composites after hydrothermal treatment reaches 2.66 mmol/g, which is larger than that of Mg-MOF-74 (2.39 mmol/g) under the same condition. XRD patterns and SEM images of the composites demonstrate that the hydrothermal stability and CO2 adsorption performance of the composites were improved compared with those of pristine Mg-MOF-74 after hydrothermal treatment.

Stable and efficient immobilization of bi-enzymatic NADPH cofactor recycling system under consecutive microwave irradiation.

One of the challenges in biocatalysis is the development of stable and efficient bi-enzymatic cascades for bio-redox reactions coupled to the recycling of soluble cofactors. Aldo-keto reductase (LEK) and glucose dehydrogenase (GDH) can be utilized as the NADPH recycling system for economic and efficient biocatalysis of (R)-4-chloro-3-hydroxybutanoate ((R)-CHBE), an important chiral pharmaceutical intermediate. The LEK and GDH was efficiently co-immobilized in mesocellular siliceous foams (MCFs) under microwave irradiation (CoLG-MIA). while they were also co-immobilized by entrapment in calcium alginate without MIA as control (CoLG-CA). The relative activity of CoLG-MIA was increased to 140% compared with that of free LEK. The CoLG-MIA exhibited a wider range of pH and temperature stabilities compared with other preparations. The thermal, storage and batch operational stabilities of microwave-assisted immobilized LEK-GDH were also improved. The NADPH recycling system exhibited the potential as the stable and efficient catalyst for the industrial preparation of (R)-CHBE.

Biomimetic Synthesis and Evaluation of Interconnected Bimodal Mesostructured MSF@Poly(Ethyleneimine)s for Improved Drug Loading and Oral Adsorption of the Poorly Water-Soluble Drug, Ibuprofen.

PurposeThe aim of this study was to improve the oral bioavailability and anti-inflammatory activity of the poorly soluble drug ibuprofen (IBU) by employing a new kind of poly(ethyleneimine)s (PEIs)-based mesocellular siliceous foam (MSF) called B-BMSF@PEI as drug carrier.MethodsB-BMSF@PEI was biomimetically synthesized by using PEIs as templates, catalysts and scaffolds under ambient conditions, and the structural characteristics, including size, morphology, mesoscopic structure and pore properties, were estimated by TEM, SEM, FTIR and N2 desorption/adsorption measurement. Then, IBU was incorporated into B-BMSF@PEI at the drug:carrier weight ratio of 1:1. The structural features of IBU before and after drug loading were systemically characterized. IBU and B-BMSF@PEI were then subject to in vitro drug release study and wettability analysis. Finally, in vivo pharmacokinetics and anti-inflammatory pharmacodynamics studies were carried out to evaluate the efficacy of B-BMSF@PEI on improving the oral adsorption of IBU.ResultsThe results demonstrated that B-BMSF@PEI was a meso–meso porous silica material with foam appearance. It consisted of uniform spherical cells (40 nm) with interconnected pore networks. IBU can be successfully loaded into B-BMSF@PEI with high efficiency (as high as 39.53%), and crystal IBU was effectively converted to an amorphous state during this process. Benefiting from the great architectures of B-BMSF@PEI, IBU/B-BMSF@PEI performed good wetting property and significantly improved the dissolution rate in both simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). Notably, IBU exhibited very satisfactory relative bioavailability (681.4%) and anti-inflammatory effects (the inhibition rates were between the ranges of 113.5% to 1504.3%).ConclusionB-BMSF@PEI with bimodal mesoporous system and interconnected nanopores was obtained owing to the dynamic self-assembly functions of PEIs. It had superiority in drug loading and could improve the oral adsorption of ibuprofen to a satisfactory level.

Developing an Electrochemical Sensor Based on Modified Siliceous Mesocellular Foam for Efficient and Easy Monitoring of Cadmium Ions

AbstractIn response to a mandatory demand to introduce sensitive technique to measure cadmium ion in ultra‐trace concentration, an electrochemical sensor by applying modified siliceous mesocellular foam (S‐MCF) with diphenylthiocarbazone as electrode material is developed. Several instrumental analysis including Fourier transform infrared spectrometry, nitrogen adsorption‐desorption examination, scanning electron microscopy, thermal evaluation and elemental analysis were applied to characterize the prepared electrode material. In the work, the prepared electrode with introduced mesoporous material is conjugated with differential pulse anodic stripping voltammetry (DP‐ASV) for ultra‐trace measurement of Cd2+ ions. Cadmium ions interact strongly with active sites of diphenylthiocarbazone and a negative potential (‐0.9 V) was applied to reduce these ions. Based on the specific characteristic of the electrochemical sensor, this electrode material was applied to pre‐concentrate target ions on the modified electrode by the prepared mesoporous material. In order to measure Cd2+ at ultra‐trace concentrations, differential pulse‐ASV was utilized to oxidize the reduced Cd ions. Two dynamic linear range (DLR) for measurement of cadmium ions at ultra‐trace concentrations were seen within ranges of 0.01 to 1.0 nmol L−1 (with sensitivity of 13.23 μA/nmol L−1) and 1.0 nmol L−1 to 10.0 nmol L−1 (with sensitivity of 0.23 μA/nmol L−1). The method detection limit (MDL) of 2.5 pmol L−1 was acquired.

Design and synthesis of a versatile cooperative catalytic aerobic oxidation system with co-immobilization of palladium nanoparticles and laccase into the cavities of MCF

We have designed a versatile reusable cooperative catalyst oxidation system, consisting of palladium nanoparticles and laccase with unprecedented reactivity. This biohybrid catalyst was synthesized by the stepwise immobilization of laccase as an enzyme and Pd as a nanometallic component into the same cavity of siliceous mesocellular foams (MCF). MCF and nanobiohybrid catalyst were characterized by BET, SAXS, SEM, EDX elemental mapping, ICP-OES, TEM, TGA, FT-IR, and XPS techniques and the stepwise immobilization of laccase enzyme and Pd onto MCF was evaluated through several compelling electrochemical studies. The present catalytic system exhibits high activity toward (i) aerobic oxidation of alcohols to the corresponding carbonyl compounds, (ii) aerobic oxidation of cyclohexanol and cyclohexanone to phenol and (iii) aerobic dehydrogenation of important N-heteocyclic compounds (tetrahydro quinazolines, quinazolonones, pyrazolines and 1,4-diydropyridines) in the presence of catalytic amount of hydroquinone (HQ) as mediator in phosphate buffer (0.1 M, pH 4.5, 4 mL)/THF (4%, 1 mL) as solvent under mild conditions. The immobilization of both oxygen-activating catalyst (laccase) and oxidizing catalyst (Pd) onto the same support makes the present catalyst system superior to other currently available heterogeneous palladium based catalytic aerobic oxidation systems.

Inorganic mesoporous silica foams for use in stabilization and controlled release of isothiazolinone-based biocides: influence of silica textural properties

The synthesis of mesocellular siliceous foam materials (MCFs) was performed at different stirring rates. In this way, foam samples composed of solid particles differing in size and morphology were obtained. Afterwards, the influence of these physical properties on the adsorptive behavior of the synthesized samples was checked for the adsorption/desorption of an isothiazolone-based commercial biocide (BIO). Results show that at low stirring rates small spheroidal particles were produced. In the absence of stirring, large blocks of silica presenting their external surface fully covered by small homogeneous silica spheres were obtained. Cauliflower-type morphologies were obtained at intermediate stirring rates, while the particle shape became irregular when the stirring rate was increased. On the contrary, the mesostructure and pore size of the particles obtained in the different samples were comparable. The biocide adsorption as well as its subsequent release in aqueous media were strongly affected by the particle size of the silica foam. Adsorption and release tests show that BIO encapsulation in silica foams preserves the biocide structure, obtaining the best performance of controlled release with the matrix synthesized at 400 rpm.

Efficient 1,3-Oxazolidin-2-one Synthesis through Heterogeneous PdII -Catalyzed Intramolecular Hydroamination of Propargylic Carbamates.

Herein, we present an operationally simple protocol for the cycloisomerization of propargylic carbamates in which a heterogeneous catalyst consisting of Pd species immobilized on amino-functionalized siliceous mesocellular foam (PdII -AmP-MCF) is used. This Pd nanocatalyst displayed high efficiency at low catalyst loading and reaction temperatures, which allowed for the efficient and mild synthesis of a wide range of 1,3-oxazolidin-2-one derivatives and related compounds. Moreover, it proved possible to re-use the Pd nanocatalyst for several reactions, although a gradual decrease in activity was observed in the subsequent cycles.

Novel calcium encapsulated mesocellular siliceous foams for crystal growth in dentinal tubules

ObjectivesThe aim of this study was to investigate the novel mesocellular siliceous foams (MCF) containing CaCO3 nanoparticles (denoted as CMCF) combined with phosphoric acid could occlude dentinal tubules through the formation of biomimetic crystal barrier. MethodsUltrastructures of MCF and CMCF were examined by transmission electron microscopy (TEM). Elemental components were analyzed with energy dispersive X-ray spectrometry (EDX). CMCF was mixed with distilled water, 10%, 20% and 30% phosphoric acid then applied on dentine discs. Crystals were characterized by X-ray powder diffractometry (XRD). The sealing efficacy of the dentinal tubules was examined by scanning electron microscopy. ResultsTEM images showed MCF presented a pore size of approximately 30.0 nm and CMCF contained abundant nano-CaCO3. Sealing efficacy showed that CMCF, when reacted with 30% phosphoric acid, would form crystals in the dentinal tubules to a depth of 83.2 ± 17.6 μm at an occlusion percentage of 75.6 ± 12.8% on average; both occlusion percentage and depth were higher than those obtained with 10% or 20% phosphoric acid (p < 0.05). The results of XRD and EDS indicated that the crystal growth in the dentinal tubules could be transformed into the biomimetic crystals. ConclusionThis study showed that the CMCF with 30% phosphoric acid could effectively occlude the dentinal tubules through the formation of biomimetic crystal barrier. Clinical significanceThe novel CMCF combined with phosphoric acid may have potential for the treatment of dentine hypersensitivity.