Synthesis of Pd-supported Nanosized Mesoporous Silica as a Spherical Nanocatalyst for Suzuki–Miyaura Coupling Reaction

Abstract

Nanosized mesoporous silica spheres with an average diameter of approximately 50 nm have been used as a catalyst support of active Pd nanoparticles, which was found to be highly efficient for Suzuki–Miyaura cross coupling compared to submicrosized or microsized conventional mesoporous silicas.

Positive effects of the residual templates within the MCM-41 mesoporous silica channels in the metal-catalyzed reactions

“…The 15 use of Pd/MCM-41(III) showed the similar high initial activity with that of the Pd/MCM-41(I), but the catalyst underwent the substantial deactivation after 30 min. No significant enhancement effect was observed when a physical mixture of the Pd/MCM-41(III) and CTABr was employed (data not shown), which 20 suggests that the close proximity of the periphery of the active Pd nanoparticles to SDA within the mesoporous channels is an essential condition. XRD and TG analysis confirmed that the framework structure and the organic content in the recovered catalyst were almost unchanged.…”

“…1,2 They have opened new possibilities as exclusively promising support materials, especially for applications in the fields of catalysis, adsorption, and materials science. [3][4][5] The ordered 20 mesoporous silicas with hexagonal (MCM-41), cubic (MCM-48), and lamellar structures (MCM-50) were first prepared by Mobil in 1992 by using alkyltrimethylammonium (C n H 2n+1 (CH 3 ) 3 N + ) surfactants as structure directing agents (SDA). 6 The surfactant assembly plays a crucial role in adjusting mesopore size, which 25 can be systematically controlled by simply changing the length of SDA.…”

“…It is well known that hydrogenation is generally believed to be a structure-insensitive reaction and the catalytic activity only 115 depends on the number of exposed surface metal species. 20,21 Thus, another factor except for the mean diameter of the Pd Additionally, Au/MCM-41 (Au: 0.5 wt%) including SDA templates was synthesized by TIE method and applied to the oxidation of alcohol to aldehyde under atmospheric molecular 30 oxygen. Since the first reports on aerobic oxidations induced by polymer-stabilized Au clusters, 22 a variety of catalytic systems including organic-and inorganic-supported Au nanoparticles have been developed.…”

“…It is well known that hydrogenation is generally believed to be a structureinsensitive reaction and the catalytic activity only depends on the number of exposed surface metal species. 20,21 Thus, factors other than the mean diameter of the Pd nanoparticles may be crucial for determining the catalytic activities. This unique phenomenon can be explained by the hydrophobicity dispersed inside the mesoporous channel induced by SDA templates, which is in favor of the interaction with organic substrates compared to the hydrophilic nature of the calcined MCM-41 without SDA templates.…”

Synthesis of hollow and rattle-type mesoporous silica spheres by treating layered mesoporous silica with a basic solution, and using the spheres as microreactors for two-phase reactions

“…Mesoporous silica materials can be produced with different shapes and structures so that they have novel functions for use in new applications. For example, nanosized particles 3,4 have been reported to be highly active catalysts 5,6 and have been used as carriers in drug delivery systems, [7][8][9] and mesoporous membranes have been used to separate gases. 10,11 A hollow sphere is an attractive shape for mesoporous silica, and many methods for fabricating hollow mesoporous silica spheres have been reported.…”