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All-solid-state lithium ion batteries (LIBs) are ideal for energy storage given their safety and long-term stability. However, there is a limited availability of viable electrode active materials. Herein, we report a truxenone-based covalent organic framework (COF-TRO) as cathode materials for allsolid-state LIBs. The high-density carbonyl groups combined with the ordered crystalline COF structure greatly facilitate lithium ion storage via reversible redox reactions. As a result, a high specific capacity of 268 mAh g À1 , almost 97.5 % of the calculated theoretical capacity was achieved. To the best of our knowledge, this is the highest capacity among all COF-based cathode materials for all-solid-state LIBs reported so far. Moreover, the excellent cycling stability (99.9 % capacity retention after 100 cycles at 0.1 C rate) shown by COF-TRO suggests such truxenone-based COFs have great potential in energy storage applications.

This work describes an all-biomass fluorescent hydrogel fabricated by functionalizing alginate (ALg) and cellulose nanofibers (CNF) hydrogels with fluorescent biomass carbon dots (CQDs) derived from glucose, xylose, and glucosamine. The biomass CQDs played dual functions in the composite hydrogels: first, endowing hydrogels with good fluorescent characters; second, enhancing the mechanical properties of hydrogels because of the cross-linking effect of the abundant oxygen-containing groups or amino groups on surface with ALg or CNF. The elastic modulus of ALg hydrogel and CNF hydrogel was increased by 4.7 times and 1.5 times, respectively, by the adding CQDs. As a proof of concept, ALg/CQDs-3 hydrogel and CNF/CQDs-3 hydrogel were used to detect Fe3+ ions and gold nanoparticle (AuNPs) in aqueous solution, showing high sensitivity. The prepared all-biomass fluorescent hydrogels hold great potential in biological imaging, biosensing, and biological monitoring fields.

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