Bifunctional Mesoporous Silica Research Articles

Bifunctional mesoporous silica solid acids for transformation of glucose to 5-hydroxymethylfurfural

Lignocellulosic biomass is a promising renewable resource that can be converted into glucose, a precursor for the synthesis of high-value bio-chemicals, such as 5-hydroxymethylfurfural (HMF). However, the conversion of glucose to HMF using conventional liquid and solid acids is challenging due to the formation of byproducts, leading to low HMF yield. In this study, bifunctional solid acid catalysts (named Al-SA-S15) consisting of aluminum (Al) as Lewis acid sites and sulfonic acid (SA) as Brønsted acid sites were prepared by direct synthesis. The catalysts were then evaluated for the transformation of glucose to HMF using a co-solvent medium of acetone and water. Among the catalysts tested, the 5Al-15SA-S15 catalyst with a Si/Al molar ratio of 5 and a 15 mol% of sulfonic acid groups achieved 95% conversion of glucose and a 51% yield of HMF. The 5Al-15SA-S15 catalyst was found to be stable under the studied conditions, with no leaching of acidic groups observed. It could be easily regenerated by washing with acetone and reused for more than five times without significant loss of performance. This study provides a deep understanding of solid acid catalysts, with precise control of acidic nature and sites for the conversion of biomass into high-value added products.

One-pot conversion of glucose to 5-hydroxymethylfurfural under aqueous conditions using acid/base bifunctional mesoporous silica catalyst

One-pot conversion of carbohydrate-derived biomass compounds to 5-hydroxymethylfurfural (HMF) using an environmentally green solvent such as water is meritorious, yet challenging, which requires the strategic design of catalysts. We prepare an ordered bifunctional organocatalyst (MS-AB) containing 3-aminopropylacetic acid grafted within the silica nanocage that converts glucose-to-HMF, exhibiting the highest HMF yield (60 wt.%/85.7 mol%) in water and under microwave conditions. Moreover, the calculated activation energies (150–170 °C) for glucose isomerization to fructose, vis-à-vis dehydration to HMF were 59.06 and 138.05 kJ mol−1, respectively which can even be comparable with the metal-catalyzed reactions. Further evidence was shown from the rate constant values, indicating fructose dehydration is faster (rate constant: k2: 1.92 x 10−2 to 1.13 x 10−1 min−1) than glucose isomerization (rate constant: k1: 2.5 to 5.3 x 10−3 min−1). Considering the advantages associated with MS-AB, the results might showcase the potential of organocatalyst for sustainable utilization of lignocellulosic biomass to platform chemicals.

Recovery of rare earth elements from NdFeB magnet by mono- and bifunctional mesoporous silica: Waste recycling strategies and perspectives

Rare earth elements (REEs) such as Nd3+ and Dy3+ were recovered from simulated and real leaching solution of the NdFeB magnet via solid phase extraction (SPE). Extraction of REEs from simulated solutions was investigated using silica functionalized with NH2-, EDTA and/or phosphonic groups. The effects of several experimental factors (pH, efficiency of adsorbents, selectivity, and elution of metal ions) on extraction of REEs were investigated. Exploiting specific affinities of adsorbents toward REEs in the presence of competing ions, selective separation of REEs was achieved successfully. The affinity of phosphorous/nitrogen containing adsorbents had the descending order of adsorption: Fe3+ > Dy3+ > Nd3+ > Ni2+ > Al3+ for multi-component systems. In the first approach, a procedure based on precipitation of Fe3+ ions combined with SPE was evaluated for the recovery of REEs in two steps. Most of the Fe3+ ions (85%) were efficiently separated by adding an ammonia solution (pH ~ 2.5). Chemical analysis of precipitate showed, though, a high content of REEs. Extraction of REEs from supernatant liquid via bi-functional mesoporous silica with EDTA and/or phosphonic groups recovered ~97.0% of Nd3+ with Ni2+ and Al3+ ions as impurities. Non-ordered silica functionalized with phosphonic groups, showed economical superiority over other mesoporous adsorbents studied for REEs extraction. Complete recovery (97.8%) of REEs was achieved after several stages of SPE with adsorbents functionalized by P/N-containing groups. The in-advance removal of Fe3+ ions was a prerequisite for successful implementation of this approach. Finally, separation of Nd3+ and Dy3+ was performed from nitric acid media using the gradient elution to obtain 98.4% purity Nd3+. The proposed step-by-step SPE procedure by P/N-containing functionalized silica was successfully applied for extraction of REEs (95.5%) in an industrial magnet. This study opens up possibilities for application of the developed approach for the End-of-Life materials recycling.

Acidity-regulated synthesis of a bifunctional mesoporous silica composite with simultaneously enhanced adsorption and catalytic performance

An Al/Cu bifunctional mesoporous silica was successfully synthesized through an acidity-regulated method. AlCl3 instead of HCl was served as catalyst for the hydrolysis and condensation of siliceous source and forming the mesostructure. Cu and Al species were then feasibly incorporated into the matrix of mesoporous SiO2 under the mildly acidic conditions. The obtained Al/Cu-SiO2 bifunctional composite preserves structural ordering of the mesopores. Al is highly dispersed and Cu nanoparticles of ca. 54 nm are decorated on Al/Cu-SiO2. The Al/Cu-SiO2 material presents large adsorption capacity, remarkable catalytic behavior and good cycling performance in the degradation of organic methylene blue from aqueous solutions.

Robust Mg(Ca)Zr-Doped Acid-Base Bifunctional Mesoporous Silica and Their Applications in the Deacetalization-Knoevenagel Reaction.

A series of Mg(Ca)Zr-doped acid-base bifunctional mesoporous silica were synthesized to study the impact of the one-step or two-step impregnation method on material structure. The two-step method seems to be a better way to synthesize metal-based functionalized catalyst and their catalytic performance is investigated using deacetalization-Knoevenagel reaction as the probe reaction. The coexisting dual active sites and suitable designing routes endowed highly efficient (Conv. >99.6%, Sel. >99.8%) and robust stability (10 consecutive cycles) of these materials. The present process succeeded in preparing catalysts decorated with acid-base sites by doping acidic and alkali metal species rather than grafting organic groups.

Influence of metal oxide and heteropoly tungstate location in mesoporous silica towards catalytic transfer hydrogenation of furfural to γ-valerolactone

One pot conversion of furfural to γ-valerolactone by transfer hydrogenation has been achieved over bifunctional mesoporous silica catalysts containing Zr and tungstophosphoric acid (TPA).

A highly sensitive immunoassay of pesticide and veterinary drug residues in food by tandem conjugation of bi-functional mesoporous silica nanospheres.

A novel type of enzyme-antibody conjugation using mesoporous silicon nanospheres (MSN) was developed, which amplified the labeling signal and highly increased the sensitivity of enzyme-linked immunosorbent assay (ELISA) for the determination of pesticide and veterinary drug residues in food. First, conjugates were prepared through layer-by-layer immobilization of an enzyme and an antibody on an MSN scaffold. Then the MSN scaffold was employed for labeling and signal amplification to develop a sensitive colorimetric immunoassay through the catalytic oxidation reaction of 5,50-tetramethylbenzidine (TMB). When this MSN-based ELISA was applied to detect chloramphenicol, avermectin, tetracycline and streptomycin in food samples, it provided linear ranges of 0.025 ng ml-1-25 ng ml-1, 0.05 ng ml-1-10 ng ml-1, 0.025 ng ml-1-10 ng ml-1 and 0.05 ng ml-1-25 ng ml-1, respectively, with low detection limits down to 0.011 ng mL-1, 0.134 ng mL-1, 0.015 ng ml-1 and 0.106 ng ml-1, respectively. For avermectin, it provided a 16.7-fold decrease of the limit of detection in contrast to that of standard ELISA without the loss of method specificity and accuracy. This novel immunoassay was hypersensitive, simple and easy-to-use, which made it high potential in applying for the accurate analysis of harmful substances in food.

Synthesis, characterization, and kinetic studies of multifunctionalized mesoporoussilica for adsorption of zinc

The aim of this study is to evaluate the utilization of bifunctional mesoporous silica with a platinum and propylsulfonic acid group (Pt/SBA15-PrSO$_{3}$H) as an adsorbent for the removal of Zn(II) ions from aqueous solutions. The SBA15-functionalized organosulfonic acid material was synthesized with a one-step cocondensation synthesis route. The second step was Pt loading during reduction and deposition into the aqueous suspension of the bifunctional mesoporous silica synthesized by an aqueous solution of formaldehyde as the reducing agent. The propylsulfonic acid and platinum functionalized mesoporous silica were characterized by BET, thermogravimetric analysis, and X-ray diffraction methods. The adsorption properties and thermodynamic parameters of the bifunctional mesoporous silica synthesized to adsorb Zn(II) ions were studied. The effects of pH, initial concentration, temperature, adsorption equilibrium, and adsorption kinetics on the adsorption of zinc were investigated using the synthesized bifunctional mesoporous silica.

N-Doped graphene quantum dot@mesoporous silica nanoparticles modified with hyaluronic acid for fluorescent imaging of tumor cells and drug delivery.

The authors describe new bifunctional mesoporous silica nanoparticles (NPs) for specific targeting of tumor cells and for intracellular delivery of the cancer drug doxorubicin (DOX). Mesoporous silica nanoparticles (MSNPs) were coated with blue fluorescent N-graphene quantum dots, loaded with the drug DOX, and finally coated with hyaluronic acid (HA). Cellular uptake of the NPs with an architecture of the type HA-DOX-GQD@MSNPs enabled imaging of human cervical carcinoma (HeLa) cells via fluorescence microscopy. The cytotoxicity of the nanoparticles on HeLa cells was also assessed. The results suggest that the NPs are higher cytotoxicity effect and exert in living cell imaging ability. Compared to the majority of other drug nanocarrier systems, the one described here enables simultaneous DOX release and fluorescent monitoring. Graphical abstract Schematic of the bifunctional mesoporous silica nanoparticles were obtained via the Stöber method, along with the doxorubicin loaded and the hyaluronic acid capped. The sensor shows good specificity and significant cytotoxicity effect on Hela cells. (TEOS: tetraethyl orthosilicate; GQDs: graphene quantum dots; DOX: doxorubicin; HA: Hyaluronic acid).

Palladium Nanoparticle Loaded Bifunctional Silica Hybrid Material: Preparation and Applications as Catalyst in Hydrogenation Reactions.

Bifunctional mesoporous silica was prepared by co-condensation of tetraethyl orthosilicate (TEOS) with functionalized organosilanes containing azides or alkoxyamines. Orthogonal functional groups at the particles were selectively addressed in subsequent chemical modifications through "click"-chemistry ("click to ligand" strategy) and radical nitroxide exchange. Palladation with PdCl2 delivered Pd nanoparticle-loaded silica material bearing sulfoxides and additional aminoamides as stabilizing ligands by means of in situ reduction of the PdII -salt. These functional particles were successfully applied to the hydrogenation of alkynes and alkenes. Aldehyde hydrodeoxygenation and benzyl ether cleavage were achieved with these hybrid catalysts under mild conditions. Particles were analyzed by IR, TEM/STEM, EDX, and solid-state NMR spectroscopy.

Synthesis and characterization of bifunctional mesoporous silica adsorbent for simultaneous removal of lead and nitrate ions

A novel acid-base bifunctional adsorbent was synthesized using a three-stage process involving (i) synthesis of MCM-41 mesoporous silica (MS) carrier, (ii) acidic modification of the carrier by aluminum isopropoxide dosing (Al-MS), and (iii) basic modification by amino groups post-grafting (Al-MS2). Large spatial hindrance amino groups were selected for the basic modification step to avoid spontaneous recombination and neutralization reactions between the two antagonist functional groups. X-ray diffraction, transmission electron microscopy, NH3-based temperature-programmed desorption, Fourier transform infrared spectroscopy, and N2 adsorption–desorption techniques were used to characterize the samples obtained at each step. Then, the simultaneous adsorption capacities of lead (Pb(II)) and nitrate (NO3−) ions were investigated and compared. The results revealed that Al-MS2 had good adsorption efficiency for Pb(II) and NO3−, achieving maximum adsorption capacities of 712μmol/g for Pb(II) and 1120μmol/g for NO3− at pH 5.0. The proposed mechanism for the simultaneous removal of Pb(II) and NO3− by the adsorbents were also discussed. The results showed that Al-MS2 was successfully modified with two antagonist adsorption groups, thus providing a new strategy for designing multifunctional adsorbents for the simultaneous removal of toxic metal cations and anions from wastewater.

Simultaneous removal of cations and anions from waste water by bifunctional mesoporous silica

A novel, bifunctional mesoporous silica (Al-SBA-15-G) capable of the simultaneous removal of cations and anions from wastewater was synthesized by the incorporation of aluminum into the framework of SBA-15 followed by the immobilization of melamine-based dendrimer groups onto the surface of the Al-substituted SBA-15. This material was characterized by XRD, SEM, TEM, NH3-TPD, FTIR, and N2 adsorption/desorption. The bifunctional Al-SBA-15-G contains a large amount of aluminum hydroxyl groups and amine groups, which were considered to be responsible for the formation of cation and anion complexes, respectively. Due to the steric effects of the melamine-based dendrimer groups, the aluminum hydroxyl and amine groups on Al-SBA-15-G keep an appropriate distance with a cooperative manner and avoid spontaneous neutralization reactions. The maximum adsorption capacities toward Cu2+ and SO42− of Al-SBA-15-G were 0.763mmol/g and 0.511mmol/g, respectively. A mechanism for the simultaneous adsorption of cations and anions by Al-SBA-15-G is proposed. As a bifunctional adsorbent, Al-SBA-15-G can potentially be used for the simultaneous removal of cations and anions from wastewater.

Synthesis and characterization of novel bifunctional mesoporous silica catalyst and its scope for one-pot deacetalization–knoevenagel reaction

Bifunctional (both sulfonic and amine functionalized) mesoporous silica catalysts were prepared by hydrothermal method. (3-[2-(2-amino ethyl amino) ethyl amino] propyl trimethoxysilane) and (3-mercaptopropyl) trimethoxysilane respectively were used as amine and sulfonic sources. The synthesised bifunctional materials were fully characterized by BET, P-XRD, 29Si CPMAS-NMR, FTIR, XPS and SEM spectral analysis. FTIR and NMR results endorse the successful grafting of organic amines and sulfonic group by surface silanol of silica. The presence of of N and S groups in the catalyst material was confirmed by the XPS spectra. Catalytic activity of the bifunctional material was tested for one-pot deacetalization–knoevenagel reaction, which gave excellent yield (95 %). Catalyst is reusable with little loss of activity up to 4 runs (<6 %).

High activity of aluminated bifunctional mesoporous silica nanoparticles for cumene hydrocracking and measurement of molar absorption coefficient

Pt/HAlMSN synthesized with Si/Al ratios = 7–50 showed high activity in cumene hydrocracking due to the Brønsted and Lewis acid sites.

ChemInform Abstract: Enantioselective Reduction of α‐Cyano and α‐Nitro Substituted Acetophenones Promoted by a Bifunctional Mesoporous Silica.

ChemInform Abstract: Enantioselective Reduction of α‐Cyano and α‐Nitro Substituted Acetophenones Promoted by a Bifunctional Mesoporous Silica.

Enantioselective Reduction of α‐Cyano and α‐Nitro Substituted Acetophenones Promoted by a Bifunctional Mesoporous Silica

Pores that put your reaction in a spin! A recoverable mesoporous silica exhibits excellent catalytic activity and enhanced enantioselectivity for the reduction of α-cyano and α-cyanoacetophenones that ascribes the synergistic effect of its phase-transfer functionalized cetyltrimethylammonium bromide and confined chiral organoiridium catalytic nature.

ChemInform Abstract: Bifunctional Mesoporous Silica Nanoparticles as Cooperative Catalysts for the Tsuji—Trost Reaction — Tuning the Reactivity of Silica Nanoparticles.

ChemInformVolume 44, Issue 21 Preparative Organic Chemistry ChemInform Abstract: Bifunctional Mesoporous Silica Nanoparticles as Cooperative Catalysts for the Tsuji—Trost Reaction — Tuning the Reactivity of Silica Nanoparticles. Arne T. Dickschat, Arne T. Dickschat Org.-Chem. Inst., Westfael. Wilhelms Univ., D-48149 Muenster, GermanySearch for more papers by this authorFrederik Behrends, Frederik Behrends Org.-Chem. Inst., Westfael. Wilhelms Univ., D-48149 Muenster, GermanySearch for more papers by this authorSabrina Surmiak, Sabrina Surmiak Org.-Chem. Inst., Westfael. Wilhelms Univ., D-48149 Muenster, GermanySearch for more papers by this authorMark Weiss, Mark Weiss Org.-Chem. Inst., Westfael. Wilhelms Univ., D-48149 Muenster, GermanySearch for more papers by this authorHellmut Eckert, Hellmut Eckert Org.-Chem. Inst., Westfael. Wilhelms Univ., D-48149 Muenster, GermanySearch for more papers by this authorArmido Studer, Armido Studer Org.-Chem. Inst., Westfael. Wilhelms Univ., D-48149 Muenster, GermanySearch for more papers by this author Arne T. Dickschat, Arne T. Dickschat Org.-Chem. Inst., Westfael. Wilhelms Univ., D-48149 Muenster, GermanySearch for more papers by this authorFrederik Behrends, Frederik Behrends Org.-Chem. Inst., Westfael. Wilhelms Univ., D-48149 Muenster, GermanySearch for more papers by this authorSabrina Surmiak, Sabrina Surmiak Org.-Chem. Inst., Westfael. Wilhelms Univ., D-48149 Muenster, GermanySearch for more papers by this authorMark Weiss, Mark Weiss Org.-Chem. Inst., Westfael. Wilhelms Univ., D-48149 Muenster, GermanySearch for more papers by this authorHellmut Eckert, Hellmut Eckert Org.-Chem. Inst., Westfael. Wilhelms Univ., D-48149 Muenster, GermanySearch for more papers by this authorArmido Studer, Armido Studer Org.-Chem. Inst., Westfael. Wilhelms Univ., D-48149 Muenster, GermanySearch for more papers by this author First published: 02 May 2013 https://doi.org/10.1002/chin.201321019Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume44, Issue21May 21, 2013 RelatedInformation

Synthesis of a core–shell–shell structured acid–base bifunctional mesoporous silica nanoreactor (MS-SO3H@MS@MS-NH2) and its application in tandem catalysis

An efficient and facile method was designed to produce an acid–base bifunctional mesoporous silica nanoreactor (MS-SO3H@MS@MS-NH2) with acid sites on the inner core, unfunctionalized silica as the neutral zone shell and basic sites on the outer shell. Such acid core–neutral zone–base shell structure design resulted in excellent spatial separation of the hostile functionalities and was better than that of the core–shell structure. The spatial order of acid sites and basic sites in the mesoporous silica nanosphere offered a designated diffusion pathway that was favorable for reaction species, while the mesoporous structure endowed the material with the confinement effect. As a result, the core–shell–shell structured mesoporous silica nanosphere was an excellent bifunctional catalyst for one-pot cascade reaction sequences.

Bifunctional mesoporous silica nanoparticles as cooperative catalysts for the Tsuji–Trost reaction – tuning the reactivity of silica nanoparticles

Bifunctional mesoporous silica nanoparticles (MSNs) bearing Pd-complexes and additional basic sites were prepared and tested as cooperative active catalysts in the Tsuji-Trost allylation of ethyl acetoacetate. Functionalization of the MSNs was realized by postmodification using click-chemistry. The selectivity of mono versus double allylation was achieved by control of reaction temperature and the nature of the catalyst.

Preparation of Bifunctional Mesoporous Silica Nanoparticles by Orthogonal Click Reactions and Their Application in Cooperative Catalysis

The synthesis of bifunctional mesoporous silica nanoparticles is described. Two chemically orthogonal functionalities are incorporated into mesoporous silica by co-condensation of tetraethoxysilane with two orthogonally functionalized triethoxyalkylsilanes. Post-functionalization is achieved by orthogonal surface chemistry. A thiol-ene reaction, Cu-catalyzed 1,3-dipolar alkyne/azide cycloaddition, and a radical nitroxide exchange reaction are used as orthogonal processes to install two functionalities at the surface that differ in reactivity. Preparation of mesoporous silica nanoparticles bearing acidic and basic sites by this approach is discussed. Particles are analyzed by solid state NMR spectroscopy, elemental analysis, infrared-spectroscopy, and scanning electron microscopy. As a first application, these particles are successfully used as cooperative catalysts in the Henry reaction.