Fig. 6
From: Sub-stoichiometric 2D covalent organic frameworks from tri- and tetratopic linkers
TEM analysis. a A PY2B-COF crystallite viewed along [001] showing the pores in the structure. b Fast Fourier Transform (FFT) filtered image of a showing the different planes in the PY2B-COF crystallite in accordance with the PXRD data. c Individual crystallites of PY2B-COF in different orientations. Multiple lattice spacings can be identified as shown. d Individual crystallites of PT2B-COF in different orientations. e Line scan analysis in the [010] direction corresponding to the turquoise outlined region in d. A small d-spacing of 1.93 nm can be identified and is similar for all four COFs showing a similar constitution of the ribbon structure. A line scan analysis with monomodal intensity variation in the [100] direction (magenta outline) is shown in f. The magenta arrows correspond to the electron rich ribbons in PT2B-COF as shown with magenta arrows in the projected potential map g of the COF. Dark contrast corresponds to higher projected potentials. h Individual crystallites of PT-COF in different orientations. Multiple lattice spacings can be identified. A line scan analysis in the [100] direction (blue outline) showing bimodal intensity variation is shown in i. The deep blue arrows correspond to the electron rich ribbons in PT-COF as shown with similar arrows in the projected potential map j of the COF, wherein dark contrast corresponds to higher projected potentials. The light blue arrow in the line scan analysis designates the bi-coordinating P linkers in PT-COF, which are more electron rich than the B linkers in PT2B- and PY2B-COFs. Scale bars: a: 20 nm; c, d, h: 50 nm
