Mesoporous silica is a versatile material for energy, environmental, and medical applications. Here, for the first time, we report a flame aerosol synthesis method for a class of mesoporous silica with hollow structure and specific surface area exceeding 1000 m2 g−1. We show its superior performance in water purification, as a drug carrier, and in thermal insulation. Moreover, we propose a general route to produce mesoporous nanoshell‐supported nanocatalysts by in situ decoration with active nanoclusters, including noble metal (Pt/SiO2), transition metal (Ni/SiO2), metal oxide (CrO3/SiO2), and alumina support (Co/Al2O3). As a prototypical application, we perform dry reforming of methane using Ni/SiO2, achieving constant 97 % CH4and CO2conversions for more than 200 hours, dramatically outperforming an MCM‐41 supported Ni catalyst. This work provides a scalable strategy to produce mesoporous nanoshells and proposes an in situ functionalization mechanism to design and produce flexible catalysts for many reactions.
Mesoporous silica is a versatile material for energy, environmental, and medical applications. Here, for the first time, we report a flame aerosol synthesis method for a class of mesoporous silica with hollow structure and specific surface area exceeding 1000 m2 g−1. We show its superior performance in water purification, as a drug carrier, and in thermal insulation. Moreover, we propose a general route to produce mesoporous nanoshell‐supported nanocatalysts by in situ decoration with active nanoclusters, including noble metal (Pt/SiO2), transition metal (Ni/SiO2), metal oxide (CrO3/SiO2), and alumina support (Co/Al2O3). As a prototypical application, we perform dry reforming of methane using Ni/SiO2, achieving constant 97 % CH4and CO2conversions for more than 200 hours, dramatically outperforming an MCM‐41 supported Ni catalyst. This work provides a scalable strategy to produce mesoporous nanoshells and proposes an in situ functionalization mechanism to design and produce flexible catalysts for many reactions.
more » « less- NSF-PAR ID:
- 10370239
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie
- Volume:
- 134
- Issue:
- 35
- ISSN:
- 0044-8249
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
Abstract Site‐selective and partial decoration of supported metal nanoparticles (NPs) with transition metal oxides (e.g., FeOx) can remarkably improve its catalytic performance and maintain the functions of the carrier. However, it is challenging to selectively deposit transition metal oxides on the metal NPs embedded in the mesopores of supporting matrix through conventional deposition method. Herein, a restricted in situ site‐selective modification strategy utilizing poly(ethylene oxide)‐
block ‐polystyrene (PEO‐b ‐PS) micellar nanoreactors is proposed to overcome such an obstacle. The PEO shell of PEO‐b ‐PS micelles interacts with the hydrolyzed tungsten salts and silica precursors, while the hydrophobic organoplatinum complex and ferrocene are confined in the hydrophobic PS core. The thermal treatment leads to mesoporous SiO2/WO3‐xframework, and meanwhile FeOxnanolayers are in situ partially deposited on the supported Pt NPs due to the strong metal‐support interaction between FeOxand Pt. The selective modification of Pt NPs with FeOxmakes the Pt NPs present an electron‐deficient state, which promotes the mobility of CO and activates the oxidation of CO. Therefore, mesoporous SiO2/WO3‐x‐FeOx/Pt based gas sensors show a high sensitivity (31 ± 2 in 50 ppm of CO), excellent selectivity, and fast response time (3.6 s to 25 ppm) to CO gas at low operating temperature (66 °C, 74% relative humidity). -
null (Ed.)Palladium catalyzed cross-coupling reactions represent a significant advancement in contemporary organic synthesis as these reactions are of strategic importance in the area of pharmaceutical drug discovery and development. Supported palladium-based catalysts are highly sought-after in carbon–carbon bond forming catalytic processes to ensure catalyst recovery and reuse while preventing product contamination. This paper reports the development of heterogeneous Pd-based bimetallic catalysts supported on fumed silica that have high activity and selectivity matching those of homogeneous catalysts, eliminating the catalyst's leaching and sintering and allowing efficient recycling of the catalysts. Palladium and base metal (Cu, Ni or Co) contents of less than 1.0 wt% loading are deposited on a mesoporous fumed silica support (surface area SA BET = 350 m 2 g −1 ) using strong electrostatic adsorption (SEA) yielding homogeneously alloyed nanoparticles with an average size of 1.3 nm. All bimetallic catalysts were found to be highly active toward Suzuki cross-coupling (SCC) reactions with superior activity and stability for the CuPd/SiO 2 catalyst. A low CuPd/SiO 2 loading (Pd: 0.3 mol%) completes the conversion of bromobenzene and phenylboronic acid to biphenyl in 30 minutes under ambient conditions in water/ethanol solvent. In contrast, monometallic Pd/SiO 2 (Pd: 0.3 mol%) completes the same reaction in three hours under the same conditions. The combination of Pd with the base metals helps in retaining the Pd 0 status by charge donation from the base metals to Pd, thus lowering the activation energy of the aryl halide oxidative addition step. Along with its exceptional activity, CuPd/SiO 2 exhibits excellent recycling performance with a turnover frequency (TOF) of 280 000 h −1 under microwave reaction conditions at 60 °C. Our study demonstrates that SEA is an excellent synthetic strategy for depositing ultra-small Pd-based bimetallic nanoparticles on porous silica for SCC. This avenue not only provides highly active and sintering-resistant catalysts but also significantly lowers Pd contents in the catalysts without compromising catalytic activity, making the catalysts very practical for large-scale applications.more » « less
-
more » « less
Abstract Chemiluminescence immunoassay exhibits high sensitivity and signal‐to‐noise ratio, thus attracting great attention in the early diagnosis and dynamic monitoring of diseases. However, the collection of conventional flash‐type chemiluminescence signal (<5 s) relies heavily on automatic sampling and reading instrument. Herein, a novel core‐satellite multifunctional chemiluminescence immunosensor is designed for the efficient enrichment and highly sensitive determination of cancer biomarker carcinoembryonic antigen (CEA) with enhanced and long‐lasting output signal that can be conveniently recorded by a simple microplate plate reading instrument. Anti‐CEA monoclonal antibody 2 (Ab2) modified Fe3O4@SiO2microspheres (Fe3O4@SiO2‐Ab2, 370 nm in diameter) are synthesized as the core for selectively capturing and enriching target CEA in solution, and anti‐human CEA monoclonal antibody 1 (Ab1) and horseradish peroxidase (HRP) co‐immobilized dendritic large‐mesoporous silica nanospheres (MSNs‐HRP/Ab1, 80 nm in diameter, pore size: 17 nm) are synthesized as the satellite for efficient immunological recognition and signal amplification. The as‐designed core‐satellite magnetic chemiluminescence immunosensors exhibit a broad linear range of 0.01−20 ng mL−1and a low detection limit of 3.0 pg mL−1for the convenient, highly specific, and sensitive determination of CEA in human serum. Such core‐satellite chemiluminescence immunosensors are expected to act as a powerful tool for in vitro detection of various biomarkers, overcome the defect of conventional chemiluminescence relying heavily on expensive and bulky automatic instruments and popularize chemiluminescence analysis to primary medical institutions and remote areas.
-
more » « less
Abstract In heterogeneous catalysis, olefin oligomerization is typically performed on immobilized transition metal ions, such as Ni2+and Cr3+. Here we report that silica-supported, single site catalysts containing immobilized, main group Zn2+and Ga3+ion sites catalyze ethylene and propylene oligomerization to an equilibrium distribution of linear olefins with rates similar to that of Ni2+. The molecular weight distribution of products formed on Zn2+is similar to Ni2+, while Ga3+forms higher molecular weight olefins. In situ spectroscopic and computational studies suggest that oligomerization unexpectedly occurs by the Cossee-Arlman mechanism via metal hydride and metal alkyl intermediates formed during olefin insertion and β-hydride elimination elementary steps. Initiation of the catalytic cycle is proposed to occur by heterolytic C-H dissociation of ethylene, which occurs at about 250 °C where oligomerization is catalytically relevant. This work illuminates new chemistry for main group metal catalysts with potential for development of new oligomerization processes.
