We report that mechanochemistry enables the synthesis of new π-conjugated covalent organic frameworks (COFs) based on naphthotetrathiophenetetracarbaldehydes 2TTN and 3TTN, expanding the scope of COF structures with two new isomeric tetradentate nodes. While recent studies have explored COF isomerism by varying bidentate linkers to tune electronic properties, the impact of node isomerism remains largely unexplored. Here, we overcome these limitations using mechanochemistry to access COFs based on insoluble fused polycyclic heteroaromatic monomers. These COFs exhibit broad absorption across the visible spectrum with 3TTN COFs showing a red-shifted absorption compared to their 2TTN-counterparts. Microwave-assisted post-modification of COFs via the Doebner reaction converts imine into quinoline linkages, enhancing the chemical stability of the COF. We explore the effect of the node structure (2TTN vs 3TTN), the network connectivity (phenylenediamine, biphenylenediamine and diquinoline) on optical band-gaps of the COFs. All COFs have shown a marked increase of electrical conductivity, by 6 orders of magnitude, upon p-doping with iodine. Quinoline-linked COF showed proton conductivity up to 1.2×10⁻3 S cm-1 at 60 °C and relative humidity of 75%. This work opens new directions for electronic modulation in COFs through node isomerism and offers a sustainable route to robust, tunable, heteroaromatic frameworks.
