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DOI: 10.1002/adma. 201503816 that the color of the mixture had changed to dark brown and the liquid acetone was transformed into solid product (Scheme 1b). This phenomenon instantly attracted our attention and a series of related work was carried out. Subsequently, the high-yield product was proved to be CQDs through some modern analysis means. Interestingly, we also find that the obtained reaction products without washing and purification can be transformed into 3D porous carbon frameworks (PCFs) through calcining at 800 C under Ar atmosphere and this 3D PCFs exhibit remarkable sodium storage performances. Here, the extremely simplified and productive synthesis procedure of CQDs and their derivative 3D porous carbon frameworks are studied. Furthermore, the corresponding mechanism of CQDs and 3D PCFs were explored. In addition, the obtained 3D PCFs was first applied as anode material for sodium-ion batteries with ultralong cycle life and outstanding rate capability. Figure 1a–c shows typical transmission electron microscope (TEM) images of the obtained CQDs. It can be clearly seen that CQDs are well dispersed with diameters in the range of 1.5–3.0 nm. Figure 1 d presents the digital image of CQD powders and ethanol solution with brown color. It is worthy to note that CQDs can be easily dispersed in ethanol without stirring or ultrasonic treatment, the resulted CQDs ethanol solution was transparent and stable, even after several months, no obvious change was observed.

The elemental composition and carbon bonding configurations of the CQDs were quantified by X-ray photoelectron spectroscopy (XPS …