Material characterization
The morphologies of Zn@Zn2(bim)4 and Zn deposition after cycling were presented by a field-emission scanning electron microscope (FESEM, JEOL 7100F) equipped with energy dispersive spectrometer (EDS, OXFORD X-MAX). The MOF layer was scraped from the in situ growth, and its 2D structure was characterized using a TEM (JEOL 2010). The crystal structure of the Zn and MOF layer was analyzed by XRD (PW1825) with Cu K𝛼 radiation. The Raman spectra were carried out with the InVia (Renishaw) Raman spectrometer with a 633 nm laser as the excitation source. The Raman for liquid solutions is taken by common procedures. For MOF decorated electrodes, the Zn@Zn2(bim)4 electrodes were cycled in symmetric cells at 0.5 mA cm-2 and 0.5 mAh 10 times, and the small amount of liquid electrolyte was wiped out using a tissue before taking the Raman test. The excitation light is focused on the electrode surface with a depth of less than 1 µm; the power of the laser beam is adjusted to be 10% of a maximum of 30 mW to avoid damage to the MOF material. The wettability of bare zinc and Zn@Zn2(bim)4 were tested by contact angles measurement (Biolin Theta). The TGA of as-prepared MnO2/CNT cathode material was conducted with a thermogravimetric analyzer (Q5000TA) with a heating rate of 5 ℃ min-1 from 20 to 800 ℃ under airflow.