Two-Dimensional Covalent Organic Framework with Synergistic Active Centers for Efficient Electrochemical Sodium Storage

Benefitingfrom the adjustable molecule structures, abundant functionalunits, large specific surface areas, and ordered pores, covalent organicframeworks (COFs) are highly desirable for electrochemical energystorage. Herein, a two-dimensional COF (denoted as HHTP-TABQ) witha fully & pi;-conjugated framework and C UN and C UOdual-active sites has been synthesized and applied as the anode inorganic rechargeable sodium-ion batteries (SIBs). During the sodium-storageprocess, it delivered remarkable rate capability, satisfactory ultra-longcycle stability (84.5% capacity retention ratio after 1000 cyclesat 5000 mA g(-1)), and facile charge exchange kinetics(2.49 x 10(-7) cm(2) s(-1)), which is superior among most reported COF-based electrodes. Furthermore,the sodiation mechanism was investigated by density functional theorycalculations and ex situ characterizations, which confirms that theelectrochemical reaction is dominated by the synergistic reactionof C UN and C UO groups. These results suggest that COFswith stable & pi;-conjugated structures, insoluble characteristics,and abundant active sites would have great potential for practicalapplications in rechargeable SIBs.