Periodic Mesoporous Organosilica Research Articles

Boron doping-induced interconnected assembly approach for mesoporous silicon oxycarbide architecture.

Despite desirable progress in various assembly tactics, the main drawback associated with current assemblies is the weak interparticle connections limited by their assembling protocols. Herein, we report a novel boron doping-induced interconnection-assembly approach for fabricating an unprecedented assembly of mesoporous silicon oxycarbide nanospheres, which are derived from periodic mesoporous organosilicas. The as-prepared architecture is composed of interconnected, strongly coupled nanospheres with coarse surfaces. Significantly, through delicate analysis of the as-formed boron doped species, a novel melt-etching and nucleation-growth mechanism is proposed, which offers a new horizon for the developing interconnected assembling technique. Furthermore, such unique strategy shows precise controllability and versatility, endowing the architecture with tunable interconnection size, surface roughness and switchable primary nanoparticles. Impressively, this interconnected assembly along with tunable surface roughness enables intrinsically dual (both structural and interfacial) stable characteristics, achieving extraordinary long-term cycle life when used as a lithium-ion battery anode.

Novel magnetic propylsulfonic acid-anchored isocyanurate-based periodic mesoporous organosilica (Iron oxide@PMO-ICS-PrSO3H) as a highly efficient and reusable nanoreactor for the sustainable synthesis of imidazopyrimidine derivatives

In this study, preparation and characterization of a new magnetic propylsulfonic acid-anchored isocyanurate bridging periodic mesoporous organosilica (Iron oxide@PMO-ICS-PrSO3H) is described. The iron oxide@PMO-ICS-PrSO3H nanomaterials were characterized by Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and field emission scanning electron microscopy as well as thermogravimetric analysis, N2 adsorption–desorption isotherms and vibrating sample magnetometer techniques. Indeed, the new obtained materials are the first example of the magnetic thermally stable isocyanurate-based mesoporous organosilica solid acid. Furthermore, the catalytic activity of the Iron oxide@PMO-ICS-PrSO3H nanomaterials, as a novel and highly efficient recoverable nanoreactor, was investigated for the sustainable heteroannulation synthesis of imidazopyrimidine derivatives through the Traube–Schwarz multicomponent reaction of 2-aminobenzoimidazole, C‒H acids and diverse aromatic aldehydes. The advantages of this green protocol are low catalyst loading, high to quantitative yields, short reaction times and the catalyst recyclability for at least four consecutive runs.

Inhibitor-self-gated stimuli-responsive anticorrosion system based on π-π stacking

Most of existing nanocontainers suffer from tedious, complicated and unsustainable assembly process which restricts their application in corrosion protection as smart inhibitor carriers. In this study, we adopted the framework-hybridization approach to prepare a smart anticorrosion system (MBT@Ph-HPMO), with MBT inhibitor as cargo and phenylene-bridged hollow periodic mesoporous organosilica (Ph-HPMO) as nanocontainer. Results reveal that the π-π stacking between MBT and framework of Ph-HPMO serves as nature valve, which is supplemented by the molecular dynamic simulation. The encapsulated inhibitor was loaded into Ph-HPMO at neutral pH, demonstrating fast release in acidic environment. On-demand release of inhibitors from MBT@Ph-HPMO contributed to achieving in situ active corrosion protection. Anticorrosion performance of MBT@Ph-HPMO for copper alloy was evaluated in 3.5 wt% NaCl solution for a period of 30 days. The alloy exhibited the slightest corrosion damage in the corrosion medium with the addition of 0.24 wt% MBT@Ph-HPMO. This facile and versatile strategy will have broad applications in new class of nanocontainers fabrication and open up a new prospect for active corrosion protection.

Visible and NIR Upconverting Er3+–Yb3+ Luminescent Nanorattles and Other Hybrid PMO‐Inorganic Structures for In Vivo Nanothermometry

AbstractLanthanide‐doped luminescent nanoparticles are an appealing system for nanothermometry with biomedical applications due to their sensitivity, reliability, and minimal invasive thermal sensing properties. Here, four unique hybrid organic–inorganic materials prepared by combining β‐NaGdF4 and PMOs (periodic mesoporous organosilica) or mSiO2 (mesoporous silica) are proposed. PMO/mSiO2 materials are excellent candidates for biological/biomedical applications as they show high biocompatibility with the human body. On the other hand, the β‐NaGdF4 matrix is an excellent host for doping lanthanide ions, even at very low concentrations with yet very efficient luminescence properties. A new type of Er3+–Yb3+ upconversion luminescence nanothermometers operating both in the visible and near infrared regime is proposed. Both spectral ranges permit promising thermometry performance even in aqueous environment. It is additionally confirmed that these hybrid materials are non‐toxic to cells, which makes them very promising candidates for real biomedical thermometry applications. In several of these materials, the presence of additional voids leaves space for future theranostic or combined thermometry and drug delivery applications in the hybrid nanostructures.

Efficient synthesis and antibacterial evaluation of some substituted β-hydroxy-1,2,3-triazoles

Abstract The purpose of this study was preparation of some various β-hydroxy-1,2,3-triazole derivatives catalyzed by copper imprinted periodic mesoporous organosilica nanocomposite (Cu/PMO NC) via multicomponent reaction in aqueous media using click chemistry. The prepared triazoles were screened in vitro for antimicrobial activity against a set of 12 microorganisms. The results of this study were shown that most of compounds had antibacterial activity against gram positive bacteria and some compounds had weak antifungal activity.

Squaramide-derived framework modified periodic mesoporous organosilica: A robust bifunctional platform for CO2 adsorption and cooperative conversion

Novel periodic mesoporous organosilica with different concentrations of squaramide-derived framework (PMO-SAF) were prepared and structurally characterized. They were applied to CO2 capture and conversion into cyclic carbonates under mild and metal/solvent-free conditions. The PMO-SAFs as prepared possess favorable structure features of high specific surface area, Lewis basic units and dual hydrogen bond donor groups, they showed interesting synergistic effects for both CO2 adsorption and epoxide activation. By regulating structure of the PMO-SAFs, an enhanced CO2 uptake capacity was obtained under a low CO2 pressure. The catalytic behaviors of PMO-SAFs on the model cycloaddition of CO2 to propylene oxide, including reaction parameters optimization, catalyst reusability and versatility were investigated in detail, and excellent yield (98%) and selectivity (99%) to propylene carbonate were obtained under the optimized reaction conditions of 90 °C and 2.0 MPa for 7.0 h. Moreover, the PMO-SAF-catalyzed reaction mechanism was proposed according to the results obtained. The special design of the PMO-SAFs endows the material with robust structure, dual-functions of CO2 adsorption and transformation, displaying great significance to the design of multi-functional nanomaterials.

Synthesis, characterization, and application of zinc supported on ionic liquid‐based periodic mesoporous organosilica (Zn@PMO-IL) in A3-coupling reaction for the synthesis of propargylamines

The present paper shows the preparation of a highly porous periodic mesoporous organosilica (PMO) including the ionic liquid pore walls that supported with zinc ions onto PMO-IL (Zn@PMO-IL). Moreover, the material was characterized using field emission‐scanning electron microscopy, transmission electron microscopy, inductively coupled plasma, and N2 adsorption–desorption. Likewise, the catalytic activity of the Zn@PMO-IL, illustrating a highly efficient nanocatalyst for the synthesis of propargylamines through three-component A3-coupling reaction of various aldehydes, amines, and arylacetylene. The results demonstrate an eco-friendly and appealing method with high efficiency and facile work-up procedure. Furthermore, the nanocatalyst can be revived by a simple filtration process and reuse at least five successive runs without considerable reducing in its activity.

Palladium Nanoparticles Incorporated Thiazoline Functionalized Periodic Mesoporous Organosilica: Efficient Catalyst for Selective Hydrogenation & Csp2−Csp2 Bond Formation Reactions

AbstractThiazoline functionalized periodic mesoporous organosilica (TPMO) supported palladium nanoparticles (Pd‐TPMO) were fabricated through a co‐condensation approach and successive incorporation of palladium nanoparticles using a double‐solvent technique. The TPMO and Pd‐TPMO were characterized through 29Si MAS NMR, FTIR, SAXS, XPS, FESEM, TEM and N2 adsorption‐desorption, which revealed the morphological and physicochemical properties of the materials. The catalytic performance of Pd‐TPMO was evaluated for hydrogenation of industrially important compounds and Csp2−Csp2 bond‐formation reactions. The Pd‐TPMO mediated catalytic reactions were found to be effective in producing the corresponding products with excellent yields and selectivity. The size and stability of palladium nanoparticles within the confined organosilica framework promotes excellent activity and recyclability of the catalyst without a significant loss in the yields for hydrogenation and Csp2−Csp2 bond‐formation reactions.

Curbed of molybdenum oxido-diperoxido complex on ionic liquid body of mesoporous Bipy-PMO-IL as a promising catalyst for selective sulfide oxidation

In this work, we introduce a novel bipyridinium ionic liquid bridged periodic mesoporous organosilicas (Bipy-PMOs-IL) which is used as the support to immobilize oxygen-rich Molybdenum (VI)-based oxido-peroxido complex (MoO(O2)2@Bipy-PMO-IL). Several techniques such as Small-angle X-ray scattering (SAXS), low angle XRD, FE-SEM (field emission scanning electron microscope), TEM (transmission electron microscope), N2 adsorption-desorption analyses (BET), atomic absorption spectroscopy (AAS), Fourier-transform infrared spectroscopy (FT-IR) and Energy Dispersive X-Ray (EDS or EDX) were used to characterize this nanomaterial. Also, the catalytic activities of the MoO(O2)2@Bipy-PMO-IL as a hybrid catalyst is tested in the selective oxidation of sulfides in water by using H2O2 (30%) as an eco-friendly and green co-oxidant. The as-prepared novel catalyst shows high to excellent performance under optimum reaction conditions at ambient room temperature. The obtained results in this work show several outstanding advantages, such as green conditions, high product yields, easy work-up, easy preparation and acceptable reusability of the catalyst for at least 5 runs. To study the IL effect in immobilization of Mo-complex, in a comparison study, the MoO(O2)2@Bipy-PMO-IL materials and MoO(O2)2@SBA-15 (with simple SiO2 body, no IL) body were employed for sulfide oxidation. After the treatment, the Mo@Bipy-PMO-IL with IL body in channels was reused for subsequent experiments (5 runs), but in Mo@SBA-15 after second run the yield was decreased dramatically.

Platinum‐Imidazolyl Schiff Base Complexes Immobilized in Periodic Mesoporous Organosilica Frameworks as Catalysts for Hydrosilylation

AbstractAn imidazolyl Schiff base‐containing periodic mesoporous organosilica (PMO) was synthesized via co‐condensation reactions between a newly prepared bis (imidazolyl)imine‐bridged bis silane and tetraethyl orthosilicate in the presence of cetyltrimethyl ammonium bromide as a soft template. The resultant as‐synthesized PMO was then employed as a solid support for platinum catalysts. This complex was fully characterized via various techniques including FTIR, solid‐state13C NMR, and 29Si‐NMR spectroscopy, as well as N2 adsorption/desorption analysis, X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) methods. In addition, the catalyst was proven to efficiently mediate hydrosilylation reactions between olefins and hydrosilanes, and it can be reused for at least five cycles without significant loss of activity.

Bifunctional Nanomaterials for Enhanced Cell Proliferation and for the Reduction of Bacterial Bioluminescence/Fitness

AbstractThis study describes the synthesis of bifunctional nanomaterials that can both inhibit bacterial bioluminescence, an indicator for the bacterial fitness, and, simultaneously, improve the proliferation of eukaryotic cells, a property that is desired for biomedical devices such as implants. To prepare this functional nanomaterial, the pores of the periodic mesoporous organosilica (PMO) nanocontainers are first functionalized with dexamethasone (Dex), which has anti‐inflammatory and cell proliferation properties. Then, the external surface of the PMO is functionalized with the antibacterial and cell adhesive bipolymer poly‐d‐lysine (PDL). The results show that cofunctionalization of the PMO surfaces with both Dex and PDL have beneficial additive and/or synergistic effects on cell proliferation and bacterial bioluminescence inhibition.

Amine-bridged periodic mesoporous organosilica nanomaterial for efficient removal of selenate

Contamination of selenate (Se(VI)), an important oxyanion, has been widely detected in numerous water sources because of its high water solubility and mobility. In this study, a family of amine-bridged periodic mesoporous organosilicas (PMOs) with tunable and high contents of amine functionality were prepared through a facile (co–)condensation approach for adsorptive removal of Se(VI). The composition, structure and properties of amine-bridged PMOs were extensively characterized using various techniques, such as scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, surface area and porosity measurement, thermo-gravimetric analysis, zeta potential measurement, and elemental analysis. The optimal amine-bridged PMO had a high amine loading of 4.04 mmol/g. The Se(VI) adsorption behaviors strongly depended on the amine content of the amine-bridged PMOs. The optimal amine-bridged PMO exhibited both fast Se(VI) adsorption kinetics and a high Se(VI) adsorption capacity of ~ 175 mg/g, because of the high amine content, uniformly distributed amine functional groups within the mesoporous skeleton, and large surface area. Furthermore, the optimal amine-bridged PMO showed robust performance for efficient removal of Se(VI) under a wide range of pH and in the presence of various common co-existing anions, and can be conveniently regenerated and reused for multiple cycles. Combined spectroscopic characterization and aqueous adsorption experiments suggested that the primary mechanism for Se(VI) removal may be attributed to the formation of outer-sphere surface complexes between Se(VI) and the surface of amine-bridged PMOs.

Cobalt nanoparticles embedded over periodic mesoporous organosilica functionalized with benzotriazolium ionic liquid for efficient and heterogeneous catalytic transformation of carbon dioxide to cyclic carbonates

Abstract A type of benzotriazolium ionic liquid-based periodic mesoporous organosilicas supported cobalt nanoparticles Co-PMO-IL (x) were prepared, characterized and applied as effective and practical heterogeneous nanocatalysts for the cycloaddition of CO2 to epoxides under solvent- and additive-free conditions. The as-prepared nanocatalysts exhibit enhanced catalytic activity for the cycloaddition, especially Co-PMO-IL (1.0) catalyst, probably due to the synergistic effects from the cobalt sites of periodic mesoporous organosilica and the basic sites (OH group/Cl anion) of the functionalized ionic liquid. The present methodology offers several advantages, such as high yields and selectivities, simple work-up, and environmentally friendly. Furthermore, the nanocatalyst could be easily recovered and reused for at least five times without any significant loss of its catalytic activity.

Multifunctional Periodic Mesoporous Organosilica Supported Benzotriazolium Ionic Liquid as an Efficient Nanocatalyst for Synergistic Transformation of CO2 to Cyclic Carbonates

AbstractAn immobilized benzotriazolium ionic liquid system has been developed for the efficient catalytic transformation of CO2 to cyclic carbonates without using any co‐catalyst or solvent. Two novel multifunctional periodic mesoporous organosilica supported benzotriazolium ionic liquids PMO‐ILTiCl5 and PMO‐ILSnCl5 were prepared, characterized and demonstrated excellent catalytic activity in the cycloaddition of CO2 with epoxides. The superior catalytic performance was observed for PMO‐ILTiCl5 in the synthesis of cyclic carbonates with high yields and selectivities. Furthermore, the catalyst PMO‐ILTiCl5 could be separated readily and reuse for at least five successful times without obvious losses in its catalytic activity, owing to the presence of intramolecular synergistic effect between active hydroxyl sites and TiCl5 nucleophile and thus provide sufficiently stable catalytic sites. Therefore, this work provided a novel strategy for highly efficient and environmentally benign catalytic conversion of CO2 to cyclic carbonates.

Hydrophobicity-Tuned Periodic Mesoporous Organo-Silica Nanoparticles for Photodynamic Therapy.

Since their invention, periodic mesoporous organosilicas (PMOs), an innovative class of materials based on organic as well as inorganic hybrid nanocomposites, have gathered enormous interest owing to their advantageous physicochemical attributes over the pristine mesoporous silica nanoparticles (MSNs). To further increase the interactions with the therapeutic guest species and subsequent compatibility as well as the physicochemical properties of PMOs, we demonstrate the post-hydroxylation of benzene-bridged PMO-based nanoparticles for photodynamic therapy (PDT). Initially, the hydrophobic benzene group in the PMO framework is modified through electrophilic substitution-assisted hydroxylation mediated by Fenton as well as Fenton-like reactions utilizing divalent and trivalent metal salts, respectively. These post-grafted PMOs with tuned hydrophobicity resulted in improved biocompatibility as well as drug loading efficiency through governing the interactions in host–guest chemistry by changing the physicochemical properties of the PMO frameworks. Furthermore, the photosensitizer, protoporphyrin IX (PpIX) molecules, encapsulated in the PMO frameworks showed a significant PDT effect in colon carcinoma (HT-29 cell line) and Gram-negative bacterial strain, Escherichia coli (E. coli). Furthermore, the light-induced cytotoxic properties in vitro are confirmed by various tests, including lactate dehydrogenase (LDH) assay for cell membrane damage and caspase assay for apoptosis determination. Indeed, the delivered PpIX molecules from PMOs generated deadly singlet oxygen species intracellularly under visible light irradiation, resulting in cell death through concomitantly triggered apoptotic caspases. Together, our findings demonstrate that this post-modified PMO design is highly advantageous and can be used as an effective PDT platform.

Polyoxometalate@Periodic mesoporous organosilicas as active materials for oxidative desulfurization of diesels

Abstract Novel material catalysts based in the active zinc-substituted polyoxotungstate ([PW11Zn(H2O)39]5-, abbreviated as PW11Zn) were efficiently used in the oxidative desulfurization of real and model diesels. These active catalytic center was strategically immobilized in a less hydrophilic periodic mesoporous organosilicas (PMOs), containing ethane-bridge (PMOE) and benzene-bridge (PMOB) walls, functionalized with (3-aminopropyl)triethoxysilane (aptes). The efficiency of the novel catalytic composites (PW11Zn@aptesPMOE and PW11Zn@aptesPMOB) was studied under oxidative desulfurization system (CODS) without the presence of an extraction solvent and also using a biphasic (diesel/extraction solvent) oxidative desulfurization system (ECODS). Both composites presented higher desulfurization efficiency under the solvent-free system, reaching ultra-low levels of sulfur compounds after only 1 h and using low ratio of H2O2/S = 4. The catalysts could be recycled without loss of activity for ten consecutive cycles. However, after the first desulfurization cycle complete desulfurization was achieved within only 30 min using PW11Zn@aptesPMOE composite. Also, the structure of PW11Zn@aptesPMOE demonstrated to be more stable than PW11Zn@aptesPMOB, probably due to the occurrence of some PW11Zn leaching from the PMOB surface, probably caused by the lower interaction of PW11Zn with the benzene-bridge PMOB wall. The most robust catalyst PW11Zn@aptesPMOE was used to desulfurize a real diesel achieving 75.9% of desulfurization after 2 h. The catalyst was further recycled with success to treat real diesel.

Preparation and Characterization of Novel Mixed Periodic Mesoporous Organosilica Nanoparticles.

We report herein the preparation of mixed periodic mesoporous organosilica nanoparticles (E-Pn 75/25 and 90/10 PMO NPs) by sol-gel co-condensation of E-1,2-bis(triethoxysilyl)ethylene ((E)-BTSE or E) with previously synthesized disilylated tert-butyl 3,5-dialkoxybenzoates bearing either sulfide (precursor P1) or carbamate (precursor P2) functionalities in the linker. The syntheses were performed with cetyltrimethylammonium bromide (CTAB) as template in the presence of sodium hydroxide in water at 80 °C. The nanomaterials have been characterized by Transmission Electron Microscopy (TEM), nitrogen-sorption measurements (BET), Dynamic Light Scattering (DLS), zeta-potential, Thermogravimetric Analysis (TGA), FTIR, 13C CP MAS NMR and small angle X-ray diffraction (p-XRD). All the nanomaterials were obtained as mesoporous rodlike-shape nanoparticles. Remarkably, E-Pn 90/10 PMO NPs presented high specific surface areas ranging from 700 to 970 m2g−1, comparable or even higher than pure E PMO nanorods. Moreover, XRD analyses showed an organized porosity for E-P1 90/10 PMO NPs typical for a hexagonal 2D symmetry. The other materials showed a worm-like mesoporosity.

Synthesis and Characterization of Novel Pyridine Periodic Mesoporous Organosilicas and Its Catalytic Activity in the Knoevenagel Condensation Reaction.

The preparation of novel organic-inorganic hybrid mesoporous organosilica containing pyridinedicarboxamide functional groups uniformly distributed inside the nanostructured pore walls has been addressed. The mesoporosity and uniformity of the synthesized nanomaterials were characterized by different techniques such as nitrogen adsorption/desorption measurements and powder X-ray diffraction (PXRD). Additionally, the presence of the pyridinedicarboxamide in the pore walls of the nanomaterials was assessed by Fourier-transform infrared spectroscopy (FT-IR), as well as 29Si and 13C solid-state cross-polarization and magic angle spinning nuclear magnetic resonance (CP/MAS-NMR). The Knoevenagel condensation of aldehydes with active methylene compounds was carried out over the pyridinedicarboxamide functionalized mesoporous organosilica, which has been proven to be an efficient heterogeneous basic catalyst in the presence of ethanol as solvent. The catalytic activity of the investigated materials was investigated in the Knoevenagel condensation between malononitrile and several benzaldehyde derivatives exhibiting a high conversion (>90%) and excellent selectivity toward the final condensation products under very mild reaction conditions. Furthermore, the catalyst stability is noteworthy as it could be recycled and reused at least twelve times without any significant change in the performance.

Lanthanide-Grafted Bipyridine Periodic Mesoporous Organosilicas (BPy-PMOs) for Physiological Range and Wide Temperature Range Luminescence Thermometry.

2,2'-Bipyridine is the most widely used chelating ligand for developing metal complexes in coordination and supramolecular chemistry. Here, we present a series of three bipyridine periodic mesoporous organosilicas (BPy-PMOs) grafted with lanthanide β-diketonate complex for the purpose of obtaining thermochromic materials, which can be employed as ratiometric temperature sensors. Such thermometers are based on the ratio of two emission intensity peaks and are not affected by factors such as alignment or optoelectronic drift of the excitation source and detectors. Three thermometric systems are studied: Dy-Dy, Tb-Sm, and Tb-Eu with the first two showing very attractive performance. For the first two systems, some of the best reported to date relative sensitivities are observed. In the BPy-PMO@Dy(acac)3 system, it is very unusual that the 4I15/2→ 6H15/2 transition is already occupied at low temperature such as 200 K, which influences its thermometric behavior. The Tb-Sm shows excellent performance in the physiological range and when suspended in water. We have additionally confirmed that the BPy-PMO hybrid materials lack toxicity to human cells, proving them very promising candidates for biomedical thermometric applications.

Tailoring Bifunctional Periodic Mesoporous Organosilicas for Cooperative Catalysis

This paper presents a novel approach to create bifunctional periodic mesoporous organosilicas containing thiol and sulfonic acid groups (SHm/SO3Hn@PMO) by co-condensation reactions of an own design...