Abstract
It is a long-standing dream to fabricate micron-sized inorganic spheres that have nanocompartments enclosed by a permeable shell and thus resemble the shape of natural cells. Here, we demonstrate a novel synthesis protocol to attain this goal for the first time. This protocol unprecedentedly harnesses interfacial sol–gel growth around Pickering droplets coupled with a surfactant assembly-directed sol–gel process within droplet-confined spaces. This protocol enables us to fabricate novel mesoporous silica microspheres (MSMs) with tunable interior architectures, such as hollow MSMs, hollow nanosphere-containing MSMs (hn@MSMs), nanosphere-containing MSMs (n@MSMs), yolk-shell-structured MSMs (y@MSMs) and “solid” MSMs. The obtained multi-compartmentalized MSMs exhibit good permeability to external molecules and good mechanical strength against stress. Moreover, their structural features benefit practical applications of CO2 capture and enzymatic reactions. Due to the high dispersion of tetraethylenepentamine and enzyme in the spatially separated nanocompartments, the developed CO2 sorbents and catalysts exhibit significantly enhanced CO2 capture efficiency and catalysis efficiency. Meanwhile, owing to the encapsulation of these nanocompartments inside the hollow micron-sized spheres, these CO2 sorbents and catalysts can be packed directly in fixed-bed reactors, which is unattainable for nanoparticle materials.
Highlights
Engineering micron-sized multi-compartmentalized systems has attracted tremendous interest from diverse fields such as catalysis[1,2], microreactors[3,4], and microencapsulation[5], due to their ability to spatially control local physical and chemical processes occurring in their interiors and due to their merits in practical applications
Synthesis of multi-compartmentalized mesoporous silica microspheres (MSMs) Siliceous materials are targeted here because they are widely used in diverse fields, and their synthesis represents a typical sol–gel chemistry
Hydrophobic silica nanospheres with diameters of 40–60 nm were used as Pickering emulsifiers [transmission electron microscopy (TEM) images, N2 sorption isotherms, and energydispersive X-ray (EDX) spectra are displayed in Supplementary Figure S1]26
Summary
Engineering micron-sized multi-compartmentalized systems has attracted tremendous interest from diverse fields such as catalysis[1,2], microreactors[3,4], and microencapsulation[5], due to their ability to spatially control local physical and chemical processes occurring in their interiors and due to their merits in practical applications. Despite intriguing results achieved from these compartmentalized structures, they are soft matter in nature and inevitably suffer from poor mechanical strength and chemical robustness, thereby severely hampering their practical applications. These drawbacks associated with these soft materials may be overcome if multi-compartmentalized inorganic microspheres can be fabricated because their frameworks consist of covalent bonds instead of molecular aggregation. Mesoporous silica particles with core-shell and yolk-shell structures have been fabricated. Their particle sizes are limited to the nanometer to submicron range[1,4]. Wei et al NPG Asia Materials (2018) 10: 899-911
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