Fig. 2

Characterization of VMS/CNW and its interfaces along with DFT investigations of growth mechanism. a-c SEM images of vertically oriented MOF nanosheets on CNWs with an increasing magnification. Scale bars = 10 μm, 4 μm, and 400 nm, respectively. The inset of (a) is the SEM image of CNW and the insets of (b) and (c) are SEM images of VMS/CNW with higher magnification. Scale bars = 800 nm, 1 μm, and 500 nm, respectively. d-f DFT-optimized structures of the most stable configurations found, for each PTA adsorption mode planar (d), vertical (e), and side (f). Vectors on each figure represent the preferred growth directions of the Ni MOF, given each type of PTA absorption mode as its constituent building blocks. Red and white balls stand for O and H atoms, respectively. Carbon atoms of the PTA molecule (graphite) are green (gray). g–i XPS spectra for CNWs, Ni MOF, and VMS/CNW interface; the inset of (h) is the coordination environment of Ni MOF and the yellow balls are for Ni atoms