Surface‐enhanced Raman scattering of carbazole‐based covalent triazine framework

A kind of carbazole‐based covalent triazine framework (CTF‐Cz) has been synthesized from a carbazole derivative. The porous polymer can efficiently adsorb probe molecules due to the strong intermolecular interactions caused by the polar triazine moiety. CTF‐Cz directly serves as the surface‐enhanced Raman scattering substrate without any post proceeding techniques. The enhancement factor of CTF‐Cz is ~105 for detecting rhodamine 6G (R6G). The lowest unoccupied molecular orbital energy level of CTF‐Cz (−3.93 eV) is much lower than that of R6G, which is in favor of the charge transfer from R6G to CTF‐Cz for illumination under a 532 nm laser, which is proved by time resolved photoluminescence spectra. The efficient charge transfer induced by the strong intermolecular π–π interactions and large molecular‐orbital delocalization contribute to the enhanced Raman signals of R6G on CTF‐Cz. The synthesized carbazole‐based covalent triazine framework (CTF‐Cz) directly serves as the metal‐free surface‐enhanced Raman scattering (SERS) substrate without additional post proceeding techniques and specific instruments, which makes Raman detection low‐cost, convenient, and easy. The SERS enhancement benefits from the molecular‐orbital delocalization promoted by the large π‐conjugated units in CTF‐Cz and the efficient charge transfer from rhodamine 6G to CTF‐Cz due to the strong intermolecular π–π interactions.