Comprehensive Study of Pore Evolution, Mesostructural Stability, and Simultaneous Surface Functionalization of Ordered Mesoporous Carbon (FDU-15) by Wet Oxidation as a Promising Adsorbent

Fuctionalization of porous carbon materials through chemical methods orientates the development of new hybrid materials with specific functions. In this paper, a comprehensive study of pore evolution, mesostructural oxidation resistance, and simultaneous surface functionalization of ordered mesoporous carbon FDU-15 under various oxidation conditions is presented for the first time. The mesostructure and pore evolution with increasing oxidative strength are retrieved from XRD, TEM, and N2 sorption techniques. The textural properties can be conveniently manipulated by changing the oxidation parameters, including different oxidative solution, temperature, and duration. It is revealed that the mesoporous carbon FDU-15 shows excellent structural stability under severe oxidation treatments by acidic (NH4)2S2O8, HNO3, and H2O2 solutions, much more stable than the mesostructural analogue CMK-3 carbon prepared by the nanocasting method. The surface area and porosity deteriorate to a large extent compared to the pristine carbon, with the micropores/small mesopores as the major contribution to the deterioration. The micropore/small mesopore can be blocked by the attached surface oxides under mild oxidation, while reopened with more carbon layer dissolution under more severe conditions. Simultaneously, high densities of surface oxygen complexes, especially carboxylic groups, can be generated. The contents and properties of the surface oxygen-containing groups are extensively studied by FTIR, TG, elemental analyses, and water and ammonia adsorption techniques. Such surface-functionalized mesoporous carbons can be used as a highly efficient adsorbent for immobilization of heavy metal ions as well as functional organic and biomolecules, with high capacities and excellent binding capabilities. Thus, we believe that the functionalized mesoporous carbon materials can be utilized as a promising solid and stable support for water treatment and organic/biomolecules immobilization and may be applicable in drug delivery, separation, adsorption technology, and columns for GC and HPLC systems in the near future

Amphiphilic Mesoporous Sandwich-Structured Catalysts for Selective Hydrogenation of 4‑Nitrostyrene in Water

Selective catalytic hydrogenation of substituted nitro compounds (NCs) of hydrophobic nature in aqueous solution using transition-metal-based catalysts is highly desirable yet fairly challenging. Herein, we propose the idea of amphiphilic mesoporous catalysts for selective hydrogenation of hydrophobic NCs in aqueous solution. The amphiphilic catalyst Co@Co–N–C@SBA-15 with a sandwich-like structure is constructed by a one-step solvent-free melting coating method. The catalyst has an external hydrophilic silica support that facilitates catalyst dispersion in water. It has unique Co–N–C catalytic layers uniformly coated in the inner mesopore surfaces of the silica support, which enhance the selective adsorption and activation of hydrophobic NCs. It has a high surface area (448.2 m2/g) and a uniform mesopore size (∼7.0 nm) for fast mass transportation. It possesses ultrafine metallic Co nanoparticles uniformly anchored within the N-doped carbon (N–C) layers for easy magnetic separation. These features make the catalyst excellent for the selective hydrogenation of 4-nitrostyrene to form 4-aminostyrene, with a high conversion of 98.0% in 1.0 h, a superior selectivity of 98.8%, and a good stability under mild conditions. A comprehensive study confirms the excellence of the amphiphilic mesoporous catalysts compared with other control catalysts. The Co–N sites are the intrinsic active sites. They can selectively adsorb and activate the nitro groups other than the vinyl groups, leading to superior selectivity. Water as the solvent results in the best performance compared with typical organic solvents probably because of an enhanced water-mediated hydrogen spillover and transfer

Ordered Mesoporous Crystalline γ-Al₂O₃ with Variable Architecture and Porosity from a Single Hard Template

In this paper, an efficient route is developed for controllable synthesis of ordered mesoporous alumina (OMA) materials with variable pore architectures and high mesoporosity, as well as crystalline framework. The route is based on the nanocasting pathway with bimodal mesoporous carbon as the hard template. In contrast to conventional reports, we first realize the possibility of creating two ordered mesopore architectures by using a single carbon hard template obtained from organic−organic self-assembly, which is also the first time such carbon materials are adopted to replicate ordered mesoporous materials. The mesopore architecture and surface property of the carbon template are rationally designed in order to obtain ordered alumina mesostructures. We found that the key factors rely on the unique bimodal mesopore architecture and surface functionalization of the carbon hard template. Namely, the bimodal mesopores (2.3 and 5.9 nm) and the surface functionalities make it possible to selectively load alumina into the small mesopores dominantly and/or with a layer of alumina coated on the inner surface of the large primary mesopores with different thicknesses until full loading is achieved. Thus, OMA materials with variable pore architectures (similar and reverse mesostructures relative to the carbon template) and controllable mesoporosity in a wide range are achieved. Meanwhile, in situ ammonia hydrolysis for conversion of the metal precursor to its hydroxide is helpful for easy crystallization (as low as ∼500 °C). Well-crystallized alumina frameworks composed of γ-Al2O3 nanocrystals with sizes of 6−7 nm are obtained after burning out the carbon template at 600 °C, which is advantageous over soft-templated aluminas. The effects of synthesis factors are demonstrated and discussed relative to control experiments. Furthermore, our method is versatile enough to be used for general synthesis of other important but difficult-to-synthesize mesoporous metal oxides, such as magnesium oxide. We believe that the fundamentals in this research will provide new insights for rational synthesis of ordered mesoporous materials

Hydrothermal Stability of Mesostructured Cellular Silica Foams

The hydrothermal stability of mesostructured cellular silica foams (MCFs) was studied in detail for the first time, using a variety of techniques including transmission electron microscopy, nitrogen sorption, small-angle X-ray scattering, 29Si solid-state nuclear magnetic resonance, and Fourier transform infrared spectroscopy. It was found that the high aging temperature, greater microporosity, and high calcination temperature contribute to the stability of MCFs in high-temperature steam. The frameworks of MCFs calcined at 550 °C are stable in 100% steam at 600 °C for 12 h, but cannot withstand more critical conditions of 800 °C steam and collapse completely. By elevating the calcination temperature of MCFs to 900 °C, the polymerization degree of the silica frameworks is further enhanced, and the obtained MCF materials exhibit high hydrothermal stability under steam at 800 °C for 12 h. The results indicate that increasing the calcination temperature is an effective method to improve the hydrothermal stability of MCFs. It is concluded that 3-D disordered MCFs show structural variations during the high-temperature steam treatments different from those of 2-D ordered hexagonal SBA-15 materials. The pore size, window size, and wall thickness were unaltered for the steam-treated MCFs, while the pore size decreased and the pore wall thickness became thicker for SBA-15

Ordered Mesoporous Platinum@Graphitic Carbon Embedded Nanophase as a Highly Active, Stable, and Methanol-Tolerant Oxygen Reduction Electrocatalyst

Highly ordered mesoporous platinum@graphitic carbon (Pt@GC) composites with well-graphitized carbon frameworks and uniformly dispersed Pt nanoparticles embedded within the carbon pore walls have been rationally designed and synthesized. In this facile method, ordered mesoporous silica impregnated with a variable amount of Pt precursor is adopted as the hard template, followed by carbon deposition through a chemical vapor deposition (CVD) process with methane as a carbon precursor. During the CVD process, in situ reduction of Pt precursor, deposition of carbon, and graphitization can be integrated into a single step. The mesostructure, porosity and Pt content in the final mesoporous Pt@GC composites can be conveniently adjusted over a wide range by controlling the initial loading amount of Pt precursor and the CVD temperature and duration. The integration of high surface area, regular mesopores, graphitic nature of the carbon walls as well as highly dispersed and spatially embedded Pt nanoparticles in the mesoporous Pt@GC composites make them excellent as highly active, extremely stable, and methanol-tolerant electrocatalysts toward the oxygen reduction reaction (ORR). A systematic study by comparing the ORR performance among several carbon supported Pt electrocatalysts suggests the overwhelmingly better performance of the mesoporous Pt@GC composites. The structural, textural, and framework properties of the mesoporous Pt@GC composites are extensively studied and strongly related to their excellent ORR performance. These materials are highly promising for fuel cell applications and the synthesis method is quite applicable for constructing mesoporous graphitized carbon materials with various embedded nanophases

Fe-Mn Bimetallic Oxide-Enabled Facile Cleaning of Microfiltration Ceramic Membranes for Effluent Organic Matter Fouling Mitigation via Activation of Oxone

Membrane fouling caused by effluent organic matters (EfOM) remains a major challenge in wastewater reclamation. Herein, we report a promising catalytic microfiltration ceramic membrane (CM) that features with ∼20 μm thickness of Fe-Mn bimetallic oxide (Mn1.5FeO6.35) active layer coating on the α-Al2O3 membrane base (α[email protected] CM), which enables fantastic mitigation of irreversible EfOM fouling via in situ Oxone activation. Modeling results indicated that complete and standard pore blocking dominated an initial fouling mechanism on the α[email protected] CM, followed by a cake mode as the fouling evolution. Critically, the cake fouling layer was effectively removed through a facile on-line cleaning with Oxone aqueous solutions, resulting in rapid flux restoration. The mechanism was dominated by radical cleaning pathways, and hydroxyl radicals (HO·) played a critical role in reducing EfOM fouling over other reactive species (e.g., sulfate radicals (SO4·–) and singlet oxygen (1O2)). A key feature of as-prepared α[email protected] CM is the favorable slightly basic pH cleaning conditions (∼pH 10), restricting Fe and Mn leaching and maximizing the membrane-sustained activity and durability. Hence, this study highlights the robust cleaning capability of α[email protected] CM toward EfOM fouling and proposes a new strategy in developing environmentally friendly catalytic CMs for wastewater reclamation

Highly Specific Enrichment of Glycopeptides Using Boronic Acid-Functionalized Mesoporous Silica

A novel boronic acid functionalized mesoporous silica, which holds the attractive features of high surface area and large accessible porosity, was developed to enrich glycopeptides. This is the first time that mesoporous material has been introduced into glycoproteome. In comparison to direct (traditional) analysis, this novel method enabled 2 orders of magnitude improvement in the detection limit of glycopeptides. The unbiased nature of organo-boronic acid groups also made this method applicable to all kinds of glycopeptides regardless of their sizes, structures, and hydrophilicities

Rapid and Efficient Removal of Microcystins by Ordered Mesoporous Silica

To alleviate the environmental and health threats from water resources polluted by large-sized microcystins (MCs), we demonstrate for the first time that ordered mesoporous silica materials with large pore sizes of 2–12 nm can be used as adsorbents for rapid and efficient removal of MCs. The obvious correlations between adsorption performance of MCs and physicochemical properties of adsorbents including pore mesostructure, texture and size, and surface chemistry have been well established. Accordingly, an excellent candidate, mesoporous silica SBA-15 templated from Pluronic P123 has been sorted out, exhibiting extremely rapid rate (one minute) as well as high capacities of 5.99 and 13 mg g–1 for removing high-concentration MC-LR and MC-RR, respectively, which are much higher than that of other silica-based adsorbents reported previously. The adsorption performance can be further improved from 50 to 95% at around pH 4 by grafting positively charged and/or hydrophobic groups onto pore surface of SBA-15. Furthermore, thermodynamic and kinetic evaluations provide additional valuable information for a better understanding of the adsorption process. Given the excellent adsorption performance, it is expected that mesoporous silica materials with unique characteristics are attractive for actual applications in removal of MCs from wastewater

Free-Standing Mesoporous Carbon Thin Films with Highly Ordered Pore Architectures for Nanodevices

We report for the first time the synthesis of free-standing mesoporous carbon films with highly ordered pore architecture by a simple coating–etching approach, which have an intact morphology with variable sizes as large as several square centimeters and a controllable thickness of 90 nm to ∼3 μm. The mesoporous carbon films were first synthesized by coating a resol precursors/Pluronic copolymer solution on a preoxidized silicon wafer and forming highly ordered polymeric mesostructures based on organic–organic self-assembly, followed by carbonizing at 600 °C and finally etching of the native oxide layer between the carbon film and the silicon substrate. The mesostructure of this free-standing carbon film is confirmed to be an ordered face-centered orthorhombic Fmmm structure, distorted from the (110) oriented body-centered cubic Im3̅m symmetry. The mesoporosity of the carbon films has been evaluated by nitrogen sorption, which shows a high specific BET surface area of 700 m2/g and large uniform mesopores of ∼4.3 nm. Both mesostructures and pore sizes can be tuned by changing the block copolymer templates or the ratio of resol to template. These free-standing mesoporous carbon films with cracking-free uniform morphology can be transferred or bent on different surfaces, especially with the aid of the soft polymer layer transfer technique, thus allowing for a variety of potential applications in electrochemistry and biomolecule separation. As a proof of concept, an electrochemical supercapacitor device directly made by the mesoporous carbon thin films shows a capacitance of 136 F/g at 0.5 A/g. Moreover, a nanofilter based on the carbon films has shown an excellent size-selective filtration of cytochrome c and bovine serum albumin