Synthesis and bifunctional catalysis of metal nanoparticle-loaded periodic mesoporous organosilicas modified with amino groups

Abstract

The present article describes the development of a periodic mesoporous organosilica (PMO)-based bifunctional catalyst that includes both oxidative and base catalytic activities. Periodic mesoporous ethylenesilica (PME) was selected as a catalyst support and modified with ethylenediamine through epoxidation of bridging ethylene moieties and the following nucleophilic addition in order to construct base sites. FT-IR measurements for the resulting material, PME-ED, reveal the successful introduction of amino groups into the bridging ethylene moieties. PME-ED can promote Knoevenagel condensation between benzaldehyde and various active methylene compounds as a solid base catalyst. The scope of applicable active methylene compounds in this catalytic system shows the base strength of PME-ED, in which a proton can be abstracted from diethyl malonate (pK a : 16.4) but not from benzyl cyanide (pK a : 21.9). Moreover, the generation of bifunctional catalytic properties to promote a one-pot tandem reaction consisting of alcohol oxidation and Knoevenagel condensation is realised by loading of Au nanoparticles within PME-ED. This catalyst design methodology can be also extended to developing another bifunctional catalyst that is composed of Pd nanoparticles and PME modified with N,Ndimethylethylenediamine in order to promote a Tsuji-Trost reaction.

Recent advanced development of metal-loaded mesoporous organosilicas as catalytic nanoreactors

“…The results showed catalytic activity with considerable to excellent conversions and yields. 252 More recently, gold-loaded mesoporous organosilica-silica core-shell NPs as catalytic nanoreactors were rationally designed and successfully synthesized (Scheme 19). 253 A thiolfunctionalized mesoporous organosilica nanosphere (MON) as the core and as the capturing center for Au(III) ions and pure mesoporous silica (MS) as the shell formed core-shell structured SH-MON@MS.…”

Facile synthesis of licarin A from isoeugenol using Cu ion‐exchanged zeolite Y under mild conditions

“…11,12 Transition metals are known for their catalytic properties, and cerium ammonium nitrate has proven to be the most effective catalyst for licarin A selective conversion from isoeugenol. [13][14][15][16][17][18][19][20][21][22][23] However, this approach utilizes homogeneous catalysts with a lack of recyclability, and costly, as well as hazardous reagents. To resolve these challenges, there is a growing interest in the development of novel recyclable heterogeneous catalysts.…”

“…Recently, significant interest has been shown in converting homogeneous to heterogeneous catalysts by immobilizing transition metals into porous materials. 13,16,17,19,20 Among these materials, zeolites Y have gained prominence as viable hosts for complex transition metals due to their notable characteristics, such as their large cage dimensions of approximately 1 nm and a window size measuring 7.4 Å, have emerged as suitable hosts for complex transition metals. Consequently, various transition metals have been encapsulated or ion-exchanged with zeolite Y to synthesize catalysts widely applied in numerous chemical reactions.…”

Surface-Functionalized Mesoporous Nanoparticles as Heterogeneous Supports To Transfer Bifunctional Catalysts into Organic Solvents for Tandem Catalysis

“…Recently, mesoporous silica nanoparticles (MSN) with hierarchical pores or dendritic pores were reported to be good supports for enzyme immobilization. − In addition, mesoporous materials were particularly explored to accommodate two catalytic species into their hierarchical structures for cascade catalysis . Since there is no need to purify and isolate intermediates, such a bifunctional system can reduce operation time, production cost, and waste, and meanwhile enhance overall yield. , Many groups have adopted this concept by combining metal particles (e.g., Ru, Au, Pt, and Pd) with other active species on the porous surface, , achieving exceptional cascade productivity toward, for instance, Knoevenagel condensation and oxidation of cinnamyl alcohol . Despite these successes, enzymes are sparingly combined with metal particles or organocatalysts for the same principle, because the incorporation of these distinct species (e.g., different stability and size) into a size-restricted porous material remains a challenge to date.…”