Spherical Mesoporous Materials from Single to Multilevel Architectures

Abstract

CONSPECTUS: Mesoporous materials with various structures have attracted considerable attention due to their distinctive properties such as large pore sizes, high surface areas, tunable pore structures, and controllable framework compositions. Among them, spherical mesoporous materials (SMMs) are of great interest owing to the unique spherical shape, which show the closed packing nature and lowest surface energy. The open mesopores and short channels of SMMs not only increase the density of high accessible active sites but also facilitate the mass diffusion with short length. These characteristics are particularly useful for applications in catalysis, adsorption, energy storage and conversion, biomedicine, and so on. In addition, the creation of a spherical shape is conformable to the law of natural selection because objects in nature tend to minimize energy, while the sphere is one of the most perfect matter structures. Therefore, the design and synthesis of SMMs are very important from both fundamental and technological viewpoints. Compared to the simple single-level, SMMs with more complex multilevel structures inevitably bring unusual mechanical, electrical, and optical properties, which are highly desired for practical applications. For example, the construction of core−shell structured SMMs has inspired great attention as they can combine multiple components into one functional unit, exhibiting ameliorated or new physicochemical properties, which cannot be obtained from the isolated one. The presence of a hollow cavity in the yolk−shell structure allows sufficient exposure of the core while maintaining the protective ability of the shell, which is conducive to retaining the distance-dependent properties of the core. Multishelled hollow structures consisting of two or more mesoporous shells are expected to show superior activities in various applications compared to their bulk counterparts because more active interfaces and unique compartmentation environments can be provided. Therefore, SMMs from single to multilevel structure represent a class of advanced nanostructured materials with unique structures and fascinating properties. In this Account, we highlight the progresses on the synthesis and applications of SMMs from single to multilevel architectures. The synthetic strategies have been summarized and categorized into (i) the modified Stober method, (ii) the hydrothermal strategy, (iii) the biphase stratification approach, (iv) the nanoemulsion assembly method, (v) the evaporation induced aggregating assembly (EIAA) method, and (vi) the confined self-assembly strategy. Special emphasis is placed on the synthetic principles and underlying mechanisms for precise control of SMMs over the particle sizes, pore sizes, pore structures and functionalities as well as different levels of architectures. Moreover, the implementation performances in catalysis, drug delivery, and energy related fields have been highlighted. Finally, the opportunities and challenges for the future development of SMMs in terms of synthe...

Recent advances in carbon-based supercapacitors

“…Alternative carbon precursors encompass conventional biomasses and phenolic resins as well as novel organic salts/polymers such as metal salts, metal-organic frameworks (MOFs), covalent organic frameworks, conjugated microporous polymers, hypercrosslinked polymers, ionic liquids and poly(ionic liquid)s, etc. [13][14][15][16] High flexibility in the precursor choice and condition regulation can customize ideal porous carbon electrodes with the following structural superiorities: (a) large surface area to guarantee a vast accumulation platform for high energy storage, coupled with abundant adsorbing sites exposed on the surface topography to improve the accessible surface area; 17,18 (b) tunable pore structures to ensure the rapid transmission of electrolyte ions and continuous infiltration into the electrode surface, thereby enabling higher power delivery; 11,19,20 (c) surface wettability/activity to boost the electrolyte/electrode interfacial contact and afford more active sites for improved charge accumulation and ion kinetics; [21][22][23] and (d) stable conductive frameworks for long-term operation. 7,24,25 In the following sections, we focus on the recent advances in the two core components (i.e., electrodes and electrolytes) of CSs.…”

“…31 Creating abundant adsorbing sites exposed on the surface topography helps to relieve the barrier toward surface accessibility for improving the storage capacity. 18 Therefore, considerable research efforts have focused on fabricating diverse carbon morphologies with refined control over the surface topography and interior texture. Spherical carbon nanoarchitectures featuring the smallest surface-to-volume ratio and close-packing nature can be constructed by various synthesis methods such as emulsion polymerization, modified Stöber synthesis, self-assembly, and hydrothermal carbonization.…”

“…Spherical carbon nanoarchitectures featuring the smallest surface-to-volume ratio and close-packing nature can be constructed by various synthesis methods such as emulsion polymerization, modified Stöber synthesis, self-assembly, and hydrothermal carbonization. 18,32 Recently, uniform mesoporous carbon nanospheres with large accessible pores (5-37 nm) were prepared through a versatile nanoemulsion polymerization process with dopamine as the precursor and PEO 106 -PPO 70 -PEO 106 (F127) as the template in a water/ethanol system ( Fig. 3a).…”

“…Generally, external-templating strategies offer precise control over diverse morphologies as mentioned above, and they can be further extended to build core-shell/hollow and other complex nanoarchitectures that synergize the accessible interior spaces/active interfaces into a single system. 18,56,57 For example, Yu's group reported a new rigid-interface-induced outward contraction approach to fabricate hollow mesoporous carbon nanocubes with MOF as the precursor (Fig. 5a).…”

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“…In designing spherical architectures, mesoporous materials have received considerable attention for various applications from nanocatalysis and energy storage and conversion to biomedicine . Among them, spherical mesoporous‐silica‐based particles have several attractive properties, such as narrow size distribution; ordered porous structure; large pore volume and surface area; and, particularly, a tunable surface chemistry, which allow the immobilization of biomolecules .…”