Abstract
It is highly desirable to design hollow structures with multi-scale functions by mimicking cells for the construction of micro/nanoreactors. Herein, we report the construction of hollow-structured submicrometer-photoreactors with bimetallic catalysts loaded within mesoporous silicas. The synthesis parameters are optimized to study the evolution of hollow structure through hydrothermal treatment and an ‘adhesive-contraction’ formation mechanism is proposed. AuPt@HMZS catalysts exhibited a broader absorbance region under visible light and the adsorption edge displayed a red-shift, indicating the strong metal–metal interactions at the alloy interface. The reaction performance of the coupled Au-Pt catalysts can be tuned to achieve excellent catalytic activity in cinnamyl alcohol oxidation to cinnamic acid for 3.1 mmol g−1 with 99% selectivity. The proposed strategy to build hollow structures as multifunctional micro/nanoreactors is promising for the design of high-performance and sustainable catalysts for chemical synthesis.
Highlights
Oxidation of primary alcohols to carboxylic acids is of importance in both organic chemistry and the chemical industry because the oxidation products can be used to prepare various pharmaceuticals and useful chemicals [1,2]
The synthesis parameters are optimized to study the evolution of hollow structure through hydrothermal treatment and an ‘adhesive-contraction’ formation mechanism is proposed
Bimetallic Au and Pt catalysts would be desirable by combining the advantages of both surface plasmonic resonance (SPR) effect on Au and activation effect on Pt to further enhance the efficiency for catalytic oxidation under visible light irradiation
Summary
Oxidation of primary alcohols to carboxylic acids is of importance in both organic chemistry and the chemical industry because the oxidation products can be used to prepare various pharmaceuticals and useful chemicals [1,2]. Coating a layer of SiO2 on the surface of ZIF-8 and subsequent hydrothermal treatments generates a hollow ‘nanoreactor’, namely, hollow mesoporous zinc silica (HMZS). These distinctive features of the AuPt@HMZS catalysts are concluded as follows: (i) the hollow void between AuPt particles and shell can provide a homogeneous chemical microenvironment for photocatalytic oxidation reaction; (ii) the formation of hollow structure can enhance the light-harvesting process through multiple light scattering; (iii) the generation of hierarchical micro-mesoporous-macroporous structure can facilitate electron-hole transportation, the adsorption of reactants and the desorption of the products; (iv) the agglomeration of catalytic AuPt particles can be suppressed via the protection of the outer shell.
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