Surface Stepwise Assembly of Self‐Cleaning Circular Polarized Luminescent Covalent Organic Framework Film

Abstract The integration of multifunctionality into covalent organic framework (COF) films remains a significant synthetic challenge. This work employs a surface stepwise modification strategy to fabricate chiral hydrophobic COF films ( R ‐/ S ‐BtBh‐COFilm ^H ) that successfully unify self‐cleaning and circularly polarized luminescence (CPL) properties within a single material platform. The first use of a liquid‐phase epitaxial stepwise spraying method for CPL‐active COF films enables the synthesis of two highly crystalline COF films (BtBh‐COFilm and TpBh‐COFilm) with exceptional surface uniformity and flatness. In situ quartz crystal microbalance (QCM) monitors the surface stepwise growth process of BtBh‐COFilm, while thermochromic fluorescence studies implicates hydrogen bond restructuring as the driver of thermal responsiveness. The resulting R ‐ and S ‐BtBh‐COFilm ^H demonstrate remarkable self‐cleaning against dye contaminants and highly CPL activity with g _1um of 6.1 × 10 ⁻² . Laser‐written patterned 2D barcodes on R ‐BtBh‐COFilm ^H further achieve durable information encryption with resistance to chemical corrosion, showcasing their potential anti‐counterfeiting utility. This study establishes a blueprint for multifunctional COF films design and advances the chiral photonic materials with environmentally adaptive properties.