Covalent Quinazolinone Frameworks via Direct and Post‐Synthetic Linker‐Exchange Synthesis: Iodine Capture and Antibacterial Activity

ABSTRACT We report the synthesis of new covalent quinazolinone‐linked frameworks (CQFs) via two metal‐free routes: direct oxidative cyclization (d‐CQFs) and post‐synthetic linker exchange (t‐CQFs). The direct route affords amorphous polymers, whereas the linker‐exchange method exploits the reversibility of imine precursors to preserve crystallinity and surface areas up to 1516 m 2 g −1 . Structural characterization of the CQFs confirmed the successful formation of the quinazolinone motif across both methodologies. The CQFs demonstrate high affinity for iodine, arising from strong donor‐acceptor interactions with pore‐confined polyiodides (I 3 − , I 5 − ), leading to a capture capacity of up to 4.54 g g −1 . Furthermore, the iodine‐loaded CQFs serve directly as highly effective antibacterial agents, delivering dose‐dependent inhibition of E. coli and S. aureus in both contact and contactless assays. This work not only introduces a new linker chemistry but also establishes both amorphous and crystalline CQFs as a robust, dual‐action platform for stable iodine capture and sustained iodine release for antibacterial action.