Laser-induced in-situ growth of luminescent ETTA-BTD covalent organic frameworks

Covalent organic frameworks (COFs) possess highly tailorable optical properties and hold significant potential for photonic applications. However, their fabrication typically relies on high-temperature and long-duration reactions, which limit spatially controlled growth at the microscale. Here, we report a purely light-driven in situ growth strategy based on a focused 473 nm continuous wave laser. Localized photothermal fields generated at the solid-liquid interface induce rapid crystallization inside an ETTA-BTD precursor, leading to the formation of micron and nanoscale COF structures with strong blue photoluminescence within seconds. This process proceeds without global heating or chemical activation. By tuning the laser power and scanning trajectories, high-precision fluorescent micropatterns can be directly scribed. This approach provides a simple and efficient optical fabrication route for applications of COFs in optical encoding, integrated photonic devices, and anti-counterfeiting technologies.