Mechanochemistry has been recognized as an efficient and sustainable methodology to provide a unique driven force and reaction environments under ambient and neat conditions for the construction of functionalized materials possessing promising properties. Among them, highly porous conjugated scaffolds with attractive electronic conductivities and high surface areas are one of the representative categories exhibiting diverse task-specific applications, especially in electrochemical energy storage. In recent years, the mechanochemistry-driven procedures have been deployed to construct conjugated scaffolds with engineered structures and properties leveraging the tunability in chemical structures of building blocks and polymerization capability of diverse catalysts. Therefore, a thorough review of related works is required to gain an in-depth understanding of the mechanochemical synthesis procedure and property-performance relationship of the as-produced conjugated scaffolds. Herein, the mechanochemistry-driven construction of conjugated porous networks (CPNs), the carbon-based materials (e.g., graphite and graphyne), and carbon supported single atom catalysts (CS-SACs) are discussed and summarized. The electrochemical performance of the afforded conductive scaffolds as electrode materials in supercapacitors and alkali-ion batteries is elucidated. Finally, the challenges and potential opportunities related to the construction of conjugated scaffolds driven by mechanochemistry are also discussed and concluded.
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High-entropy alloy nanoparticles (HEA-NPs) are highly underutilized in heterogeneous catalysis due to the absence of a reliable, sustainable, and facile synthetic method. Herein, we report a facile synthesis of HEA nanocatalysts realized via an ultrasound-driven wet chemistry method promoted by alcoholic ionic liquids (AILs). Owing to the intrinsic reducing ability of the hydroxyl group, AILs were synthesized and utilized as environmentally friendly alternatives to conventional reducing agents and volatile organic solvents in the synthetic process. Under high-intensity ultrasound irradiation, Au3+, Pd2+, Pt2+, Rh3+, and Ru3+ ions were co-reduced and transformed into single-phase HEA (AuPdPtRhRu) nanocrystals without calcination. Characterization results reveal that the as-synthesized nanocrystals are composed of elements of Au, Pd, Pt, Rh, and Ru as expected. Compared to the monometallic counterparts such as Pd-NPs, the carbon-supported HEA nanocatalysts show superior catalytic performance for selective hydrogenation of phenol to cyclohexanone in terms of yield and selectivity. Our synthetic strategy provides an improved and facile methodology for the sustainable synthesis of multicomponent alloys for catalysis and other applications.
Fluorinated porous organic networks (F-PONs) have demonstrated unique properties and applications, but approaches capable of affording F-PONs with high fluorine content and robust nanoporous architecture under metal-free and easy handling conditions are still rarely reported. Herein, using polydivinylbenzene (PDVB) as an easily available precursor, a novel and straightforward approach was developed to afford F-PONs via a dehydrative Friedel-Crafts reaction using perfluorinated benzylic alcohols as the cross-linking agent promoted by Brønsted acid (trifluoromethanesulfonic acid). The afforded material (F-PDVB) featured high fluorine content (22 at.%), large surface area (771 m2·g-1), and good chemical/thermal stability, rendering them as promising candidates for the adsorption of CO2, hydrocarbons, fluorocarbons, and chlorofluorocarbons, with weight capacities up to 520 wt.% being achieved. This simple methodology can be extended to fabricate fluorinated hyper-crosslinked polymers (F-HCPs) from rigid aromatic monomers. The progress made in this work will open new opportunities to further expand the involvement of fluorinated materials in large scale applications.
Since Haruta et al. discovered that small gold nanoparticles finely dispersed on certain metal oxide supports can exhibit surprisingly high activity in CO oxidation below room temperature, heterogeneous catalysis by supported gold nanoparticles has attracted tremendous attention. The majority of publications deal with the preparation and characterization of conventional gold catalysts (e.g., Au/TiO2), the use of gold catalysts in various catalytic reactions, as well as elucidation of the nature of the active sites and reaction mechanisms. In this overview, we highlight the development of novel supported gold catalysts from a materials perspective. Examples, mostly from those reported by our group, are given concerning the development of simple gold catalysts with single metal-support interfaces and heterostructured gold catalysts with complicated interfacial structures. Catalysts in the first category include active Au/SiO2 and Au/metal phosphate catalysts, and those in the second category include catalysts prepared by pre-modification of supports before loading gold, by post-modification of supported gold catalysts, or by simultaneous dispersion of gold and an inorganic component onto a support. CO oxidation has generally been employed as a probe reaction to screen the activities of these catalysts. These novel gold catalysts not only provide possibilities for applied catalysis, but also furnish grounds for fundamental research.