3 research outputs found

    Cellulose Nanocrystals/Carboxylated Multiwall Carbon Nanotubes/Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> Hybrid Aerogels for Electromagnetic Interference Shielding

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    Ultralight and mechanically robust materials with high-efficiency electromagnetic interference (EMI) shielding performance are imperative to meet the evolution of portable electronic equipment. However, it remains challenging to balance ultralight and robust mechanical performances with excellent EMI shielding properties. Herein, anisotropic cellulose nanocrystals/carboxylated multiwall carbon nanotubes/Ti3C2Tx MXene (CCM) hybrid aerogels are fabricated by methyltrimethoxysilane treatment and unidirectional freeze-drying. Successful assembly of multidimensional nanomaterials through Si–O–Si nanoribbons helps to realize lightweight, hydrophobicity, thermal insulation, and mechanical properties, as well as high electrical conductivity. The obtained hybrid aerogel displays a residual height of 76.38% at 50% strain after 50 compression cycles and a water contact angle of 120.7° in the axial direction. The average specific EMI shielding effectiveness of the anisotropic cellulose nanocrystals/carboxylated multiwall carbon nanotubes/Ti3C2Tx MXene hybrid aerogel could reach up to 14,030.22 dB·cm2·g–1, surpassing major reported materials. Multifunctional and anisotropic hybrid aerogels are promising in the field of electromagnetic protection engineering

    Direct Synthesis of 2,5-Diformylfuran from Carbohydrates Using High-Silica MOR Zeolite-Supported Isolated Vanadium Species

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    Directly transforming carbohydrates into high value-added chemicals provides an economic and sustainable path for the utilization of the renewable biomass resource. Herein, we fabricated an efficient catalytic system for the straightforward conversion of various carbohydrates into 2,5-diformylfuran (DFF) by using vanadium oxide supported on high-silica mordenite (MOR) zeolites in the presence of hydrochloric acid. The synthesis of high-silica MOR zeolites was achieved in a template-free dense system featuring energy savings and environmental friendliness, delivering the SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> ratio up to 80. The conversion of fructose into DFF reached a high yield of 96.0% in a one-pot and one-step reaction by oxidation with atmospheric O<sub>2</sub> (balloon), with facile recovery and good reusability of the catalyst. Good yields were also obtained in the direct synthesis of DFF from other carbohydrates including glucose, sucrose, inulin, raffinose, maltose, and starch. The high performance relied on the unique high-silica MOR skeleton, which (1) endowed the highly dispersed V species mainly in the form of isolated tetrahedrally coordinated [V<sub>2</sub>O<sub>8</sub>]<sup>6–</sup> species as the active oxidative sites and (2) provided satisfactory acidity for the formation of intermediate 5-hydroxymethylfurfural (HMF) and sufficient resistance to corrosion under an acid environment for good stability

    Three-Dimensional Ionic Covalent Organic Frameworks for Rapid, Reversible, and Selective Ion Exchange

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    Covalent organic frameworks (COFs) have emerged as functional materials for various potential applications. However, the availability of three-dimensional (3D) COFs is still limited, and nearly all of them exhibit neutral porous skeletons. Here we report a general strategy to design porous positively charged 3D ionic COFs by incorporation of cationic monomers in the framework. The obtained 3D COFs are built of 3-fold interpenetrated diamond net and show impressive surface area and CO<sub>2</sub> uptakes. The ion-exchange ability of 3D ionic COFs has been highlighted by reversible removal of nuclear waste model ions and excellent size-selective capture for anionic pollutants. This research thereby provides a new perspective to explore 3D COFs as a versatile type of ion-exchange materials
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