Spatially engineered of ionic chains in one-dimensional covalent organic frameworks for efficient uranium...

Covalent organic frameworks (COFs) exhibit significant potential for the photocatalytic reduction of U(VI), but their performance is substantially limited by intrinsic hydrophobicity and poor charge carrier mobility. Although ionic modification has proven effective in enhancing photocatalytic activity, conventional approaches often overlook the spatial arrangement of ionic sites, leading to disrupted structural order and diminished photochemical efficiency. In this work, we present a spatial site-engineering strategy to precisely introduce the placement of ionic chains inside the channels, outside the channels, or at both positions in one-dimensional COFs by controlling the orientation of the nitrogen sites in two V-shaped phenanthroline monomers. The introduction of ionic chains enhances hydrophilicity, while the asymmetric dual-site configuration preserves crystallinity, and establishes a strengthened built-in electric field that facilitates efficient exciton dissociation and directional charge transport. Owing to the balanced interplay among structural integrity, charge dynamics, and interfacial accessibility, the optimized zwitterionic COF (COF-IO-SO₃^-) exhibits an excellent U(VI) reduction performance (1806.87 mg g^-1), achieves over 95% removal of U(VI) from real uranium-mining wastewater while demonstrating excellent stability under aqueous conditions. This study establishes spatially controlled ion functionalization as a rational molecular-level design principle for advancing COF-based photocatalysts toward practical applications in uranium remediation.