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Co-based metal-organic framework (Co-MOF) nanosheets were successfully synthesized by the organic ligands with Schiff base structure. The laminated structure gives Co-MOF nanosheets a great advantage in the application in the flame retardant field. Meanwhile, -C═N- from Schiff base potentially provides active sites for further modification. In this work, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was used to modify Co-MOF (DOPO@Co-MOF) to further enhance its flame retardant efficiency. It is attractive that DOPO has a synergistic effect with Co-MOF on improving fire safety of poly(lactic acid) (PLA). The obvious decrease in the values of peak heat release (27%), peak smoke production (56%), and total CO yield (20%) confirmed the enhanced fire safety of PLA composites. The possible flame retardant mechanism was proposed based on characterization results. Moreover, the addition of DOPO@Co-MOF had a positive influence on the mechanical performance, including tensile properties and impact resistance. This work designed and synthesized two-dimensional MOFs with active groups. As-prepared Co-MOF with expected structure shows a novel direction of preparing MOFs for flame retardant application.

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Durable and efficient hydrogen evolution reaction (HER) electrocatalysts that can satisfy industrial requirements need to be developed. Platinum (Pt)-based catalysts represent the benchmark performance but are less studied for HER under high current densities in neutral electrolytes due to their high cost, poor stability, and extra water dissociation step. Here a facile and low-temperature synthesis for constructing "blackberry-shaped" Pt nanocrystals on copper (Cu) foams with low loading as self-standing electrodes for HER in neutral media is proposed. Optimized hydrogen adsorption free energy and robust interaction induced by charge density exchange between Pt and Cu ensure the efficient and robust HER, especially under high current densities, which are demonstrated from both experimental and theoretical approaches. The electrode exhibits small overpotentials of 35 and 438 mV to reach current densities of -10 and -1000 mA cm -2 , respectively. Meanwhile the electrode illustrates outstanding stability during chronoamperometry measurement under high current densities (-100 to -400 mA cm -2 ) and 1000 cycles linear sweep voltammetry tests reaching -1000 mA cm -2 . This study provides new design strategies for self-standing electrocatalysts by fabricating robust metalmetal interactions between active materials and current collectors, thus facilitating the stable function of electrodes for HER under technologically relevant high current densities.

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