Scanning Transmission Electron Microscopy (STEM) analysis was carried out in an X-Field Emission Gun (X-FEG) Titan FEI microscope operated at 300 kV. The microscope was equipped with a monochromator, a spherical aberration corrector for the electron probe, which was aligned using a gold standard sample prior the experiments, assuring a potential spatial resolution of 0.8 Å. Data collection was performed using a low angle annular dark field detector (LAADF). Due to the extremely high-sensitivity of COFs respect the electron beam, the electron dose was maintained as low as possible, below 600 e -/Å 2 . Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy: ATR-FTIR spectroscopy was performed using a Nicolet 6700 equipped with an ATR (Attenuated Total Reflectance) accessory having a spectral range of 4000-650 cm -1 . Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectra were obtained with a Bruker Tensor 27 for the COFBOTs. Solid-State 13 C CP-MAS Nuclear Magnetic Resonance Spectroscopy: Solid state NMR spectra were conducted on a Bruker 400 MHz NEO spectrometer. The 13 C CP-MAS with 1 H decoupling was performed with sample rotation speed of 12 KHz and a 4 mm rotor. The cross-polarization time was 2 ms and the total number of scans was 7168. Delays between scans were 2 s and the total measurement time was 4 h 5 min.