In summary, they demonstrated the intrinsic “intramolecular heterojunction” in CTF-1 polymer is highly selective for solar-driven methane to ethanol reaction. Such activity and selectivity can be ascribed to the intrinsic and simultaneous charge separation by the “intramolecular heterojunction”, stronger water adsorption, highly selective water-promoted C–H bond cleavage, favorable reaction sites on the benzene motif and the preferred desorption of ethanol to methanol. This work provides a novel approach for converting methane into high-value products under mild conditions. Additionally, the introduction of the new concept “intramolecular junction” offers innovative solutions to critical challenges in the design of photocatalysts.