Hydrophobic Modification of Pd/SiO₂@Single‐Site Mesoporous Silicas by Triethoxyfluorosilane: Enhanced Catalytic Activity and Selectivity for One‐Pot Oxidation

Abstract

To enhance the catalytic activity in a selective one-pot oxidation using in-situ generated H(2)O(2), a hydrophobically modified core-shell catalyst was synthesized by means of a simple silylation reaction using the fluorine-containing silylation agent triethoxyfluorosilane (TEFS, SiF(OEt)(3)). The catalyst consisted of a Pd-supported silica nanosphere and a mesoporous silica shell containing isolated Ti(IV) and F ions bonded with silicon (SiF bond). Structural analyses using XRD and N(2) adsorption-desorption suggested that the mesoporous structure and large surface area of the mesoporous shells were retained even after the modification. During the one-pot oxidation of sulfide, catalytic activity was enhanced significantly by increasing the amount of fluorine in the shell. A hydrophobic surface enhanced adsorption of the hydrophobic reactant into the mesopore, while the less hydrophobic oxygenated products efficiently diffused into the outside of the shell, which improved the catalytic activity and selectivity. In addition, the present methodology can be used to enhance the catalytic activity and selectivity in the one-pot oxidation of cyclohexane by using an Fe-based core-shell catalytic system.

Fabrication of Pd/SiO2 with Controllable Wettability for Enhanced Catalytic Hydrogenation Activity at Ambient H2 Pressure

“…This modified catalyst demonstrated significantly improved catalytic efficiency in the hydrogenation of styrene. More and more reports exhibited that the activity could be enhanced after hydrophobicity modification when nonpolar or low polar molecules were used as substrate in the reaction . The reason was simply ascribed to the accumulation of more hydrophobic substrates on the hydrophobic surface during reactions.…”

Synthesis of Ce ions doped metal–organic framework for promoting catalytic H2 production from ammonia borane under visible light irradiation

“…[13][14][15][16][17] For instance, amine-functionalized Ti-based MOFs can be applicable to photocatalytic CO2 reduction 18 and H2 production from water 19 under visible light irradiation. 21,22 The oxo-bridged hetero-metallic assemblies can not only harvest the solar light but also efficiently separate the photo-excited charges, leading to the unexpected photocatalytic performance. 20 These achievements demonstrate that MOF is a potential new class of porous material for application in versatile redox reaction.…”

Gold nanoparticle modified magnetic fibrous silica microspheres as a highly efficient and recyclable catalyst for the reduction of 4-nitrophenol

“…[4][5][6] To date, various methods have been developed for preparing NMNPs-based catalysts, among which the chemical reduction of noble metal cations in a solution using a reducing reagent is the most common preparation procedure. 8,[12][13][14][15][16] Although these mesoporous silicas have regular mesopores and high specific surface areas that can support NMNPs with high dispersion, their mesopores can always be easily blocked because of the small pore size. 10,11 To solve this problem, NMNPs have been grafted onto various supporting matrices to generate hybrid catalysts to protect against the aggregation of NMNPs.…”