Halide Ion‐Modulated Chiral Synergy in Co‐Assembled AIEgen‐CNC Composites for Circularly Polarized Luminescence

Abstract Pursuing innovative modulation strategies and high asymmetry factors ( g _lum ) remains a cornerstone in developing circularly polarized luminescence (CPL) materials. Conventional approaches employ either bottom‐up chiral small molecule self‐assembly or top‐down co‐assembly of achiral luminophores with supramolecular chiral templates (e.g., cellulose nanocrystals (CNCs), liquid crystals). These templates act as pre‐engineered “molds” to align achiral emitters within chiral matrices. However, co‐assembling chiral small molecules with such templates remains underexplored, challenged by complex protocols and limited assembly control, raising fundamental questions about supramolecular chiral interplay. Herein, we elucidate the co‐assembly and interplay between chiral aggregation‐induced emission (AIE) molecules (PN‐Phe halides) and CNCs. Halide ions (F ^– , Cl ^– , Br ^– , and PF ₆ ^– ) profoundly modulate PN‐Phe self‐assembly, dictating distinct morphologies, packing, chiroptical signals, fluorescent quantum yields (QY), and lifetimes. PN‐Phe‐Cl ^– exhibits the highest g _lum (−4.1 × 10 ⁻³ ), versus PN‐Phe‐Br ^– (−2.8 × 10 ⁻³ ). Strikingly, co‐assembly into CNC‐PVA‐PN‐Phe‐X‐ (CPP‐X‐) composite films reverse this trend: CPP‐Cl ^– achieves an exceptional g _lum of −0.43, contrasting sharply with CPP‐Cl ^– (−3.1 × 10 ⁻² ). The multiple color variations and potential application in anti‐counterfeiting demonstrate the advantages of this co‐assembly strategy. This work highlights the significant role of assembly patterns in constructing advanced CPL materials, revealing that halide ions could serve as effective modulators for CPL.