A Template Carbonization Strategy to Synthesize Ordered Mesoporous Silica Microspheres with Trapped Sulfonated Carbon Nanoparticles for Efficient Catalysis

Abstract

Ordered mesoporous materials have attracted much attention since their discovery owing to their outstanding properties, such as tunable pore sizes and mesostructures, variable morphologies, high surface areas, and large pore volumes. [1][2][3][4][5][6][7][8] These features make them promising candidates for applications including catalysis, [9] adsorption and separation, [10] chemical sensing, [11] and biomedicine. [12] To date, significant advances have been achieved in the synthesis of mesoporous materials, particularly in the soft templating approach using surfactants or block copolymers as the templates (structuredirecting agents), and enormous ordered mesoporous materials with variable pore structures, pore sizes, and framework compositions have been prepared.Apart from exploring the methods of synthesis and strategies, considerable efforts have been devoted to designing functional ordered mesoporous materials by introducing functional nanomaterials or organic groups for practical applications. For example, using sol-gel chemistry, many functional mesoporous composites have been synthesized by coating functional nanoparticles. [13,14] Furthermore, functional organic groups or nanoparticles have been introduced into mesopores, resulting in various functional mesoporous materials that are useful in drug delivery, chemical sensing, and catalysis. [15][16][17][18][19] Particularly the immobilization of sulfonic acid groups (-SO 3 H) in mesopores have aroused great research interest because the mesoporous materials can provide a large accessible surface area for supporting high density of acidic sites, thus serving as efficient solid Brønsted acids.[18] Compared to traditional homogeneous acid catalysts (such as H 2 SO 4 , AlCl 3 , BF 3 ), the novel heterogeneous catalysts are environmentally benign and can be readily recycled from reaction medium, thus reducing the energy consumption for the production of chemicals.To introduce sulfonic acid groups on the pore walls of mesoporous silica materials, typical methods involve the attachment of sulfur-containing organic silanes (for example ÀSH, ÀSÀSÀ) by post-grafting or co-condensation and subsequent oxidation with hydrogen peroxide.[20] Van Rhijn et al.[18a] first reported the synthesis of ordered mesoporous silicas functionalized with SO 3 H groups using co-condensation or post-modification. The obtained SO 3 H-functionalized mesoporous silicas exhibited good performance in catalyzing the condensation of 2-methylfuran with acetone with high conversion (85 %) and selectivity (96 %) toward the target product 2,2-bis(5-methylfuryl)propane. By contrast, traditional microporous solid acids, such as H-b and H-US-Y zeolites, exhibited much lower conversion (ca. 60 %) and selectivity (ca. 70 %) owing to the undesired fast formation and adsorption of tarry oligomeric compounds in the narrow zeolite pores and subsequent catalyst deactivation. This result suggests that the immobilization of SO 3 H groups in mesoporous silicas with larger pore is more favorable for catalysi...

Ordered Mesoporous Materials Based on Interfacial Assembly and Engineering

“…Finally, the elimination of PEO‐ b ‐PMMA and C n TAB templates in air leads to ordered dual‐mesoporous silica. Moreover, this EIAA method can also be extended to other block copolymers such as poly(ethylene oxide)‐ b ‐polystyrene (PEO‐ b ‐PS), for synthesis of large‐pore mesoporous silica spheres 207…”

Energy Landscape of Water and Ethanol on Silica Surfaces

“…Its various polymorphs may interact with small organic molecules and water, and are extensively applied in many scientific and technological fields, ranging from classic heterogeneous catalysis [4][5][6][7] to recently developed organo-silica hybrid nanodevices 8,9 . Organics encapsulated in silica nanoparticles are also employed to assist medical diagnoses and treatments 10 , such as tumor targeted drug delivery 11,12 . In all such applications, the energetics of adsorbate -surface binding is critical to function.…”

A Shear Stress Regulated Assembly Route to Silica Nanotubes and Their Closely Packed Hollow Mesostructures

“…Particularly, Davis and co-workers have firstly suggested a "silicate rod assembly" route, where randomly ordered surfactant/silicate composite nanorods can spontaneously pack into a long-range ordered hexagonal arrangement. [11][12][13][14] Previous work has mainly focused on the core/ shell-type nanostructured materials based on single spherical micelles or just their aggregated counterparts. After the first report by Templin et al, [10] diblock copolymers have become attractive alternatives in the soft-templating syntheses of ordered mesoporous materials, especially those with large pores.…”

“…After the first report by Templin et al, [10] diblock copolymers have become attractive alternatives in the soft-templating syntheses of ordered mesoporous materials, especially those with large pores. [11][12][13][14] Previous work has mainly focused on the core/ shell-type nanostructured materials based on single spherical micelles or just their aggregated counterparts. However, till now, seldom work on the cooperative self-assembly of diblock copolymers with the corresponding inorganic species into tubular mesostructures and systematic structure-directing roles of diblock copolymers in the formation of mesostructures was reported.Herein, we report an assembly route that is regulated by shear stress to fabricate uniform silica nanotubes and their closely packed hollow mesostructures.…”