However, the long-term performance of current molecular and polymeric semiconductors is low because of lacking oxidative stability and structural disorder due to the inherent degrees of freedom of their constituents. Charge carrier mobility in organic semiconductors increases as we go from 0D, aromatic molecules (≤ 50 cm 2 V -1 s -1 ) to 1D, linear, conjugated polymers (up to 600 cm 2 V -1 s -1 ). This research logically extends to covalently-bonded, layered 2D-materials often referred to as a subclass of covalent organic frameworks (COFs). In COF-type materials, strong, covalent bonds reduce in-plane disorder and weak, inter-planar van der Waals forces enable exfoliation into (atomically) thin sheets. 2D-materials, most famously graphene, have a different electronic structure than their layered analogues due to the confinement of the electron gas to the 2D-crystal. In general, semiconducting 2D materials are expected to suffer less from short channel effects making them uniquely suitable for highly miniaturized field effect transistors. Graphitic carbon nitrides form a subset of 2D, layered COFs that are semiconductors and can be exfoliated. At present, PTI and its intercalated derivatives are the best characterized graphitic carbon nitrides. They are composed of triazine (C3N3) units that are covalentlylinked in-plane by imide-bridges into layered materials with high thermal stability up to 400 °C. Because of their high nitrogen content, PTI has a high ionization potentialthat means, a high energetic difference between the vacuum level and the highest valence band -as well as a high electron affinitymeaning, a high energetic difference between the vacuum level and the lowest conduction band. As a result, PTI has a higher oxidative stability than hydrocarbon based 0D or 1D organic semiconductors. High quality PTI materials are typically obtained from ionothermal synthesis in eutectic melts of alkali halides resulting in intercalation of ions like Li + and Br -into the structure. Previously, we were able to reduce the amount of carbonaceous defect sites in poly(triazine imide) (Figure ). In the following, we combine microscopic and macroscopic characterization methods with ab initio calculations to pinpoint the reasons for the surprisingly low electroluminescence and low conductivity (10 -10 to 10 -9 S cm -1 ) of macroscopic films of PTI. We compare two types of poly(triazine imides): PTI with intercalated LiBr (PTI-LiBr), and an intercalate-free analogue (PTI-IF). Herein, (i) we elucidate the impact of de-intercalation on the structure and electronic properties of PTI using elemental analysis, powder x-ray spectroscopy (PXRD), convergent-beam electron diffraction (CBED), electron energy loss spectroscopy (EELS), ultraviolet photoelectron spectroscopy (UPS) and solid state nuclear magnetic resonance (ssNMR), (ii) we develop a model explaining the observed red-shift of electroluminescence as well as the discrepancy between the optical gap and the band gap using diffuse reflectance spectroscopy, valence band EELS, and ab initio computational data, (iii) we propose an energy level diagram on the basis of density-functional theory (DFT) calculations, evaluation of the Tauc plot and UPS, and (iv) from time-domain THz spectroscopy data we find that the nano-crystalline morphology of PTI constitutes the major bottleneck for conductivity. Interestingly, our analysis based on the phenomenological Drude-Smith model reveals an unusually high charge carrier density in both PTI-materials of and it is above and beyond that of any known intrinsic inorganic semiconductor (e.g. Ge 2.33•10 13 cm -3 ; Si 9.65•10 9 cm -3 ).