Cyclodextrin-threaded covalent organic polyrotaxanes with tunable solid-state emissive activity for efficient iodine capture

Abstract

Herein, we rationally designed and synthesized a covalent organic polyrotaxane (COPR), with aggregation-induced emission (AIE) characteristics, denoted as TPE-CD-COPR, through a two-component Knoevenagel condensation reaction, where β-cyclodextrin (β-CD) inclusion complexes served as direct building blocks. This approach yielded several remarkable improvements over conventional CD-free counterpart (TPE-COP). The threading of CD not only achieved precise tuning of solid-state emission color under UV irradiation, but also introduced significant polarity enhancement through rotaxane subunit incorporation. The incorporation of water-soluble cyclodextrin rotaxane architectures significantly enhanced the aqueous dispersibility, thereby providing an optimal solution for developing high-performance aqueous-phase iodine adsorbents. As a result, TPE-CD-COPR demonstrated significantly enhanced aqueous-phase iodine adsorption capabilities, exhibiting both superior capacity and faster kinetics compared to conventional CD-free counterpart. The enhanced I₂ adsorption capacity arises from synergistic effects of hydroxyl-rich β-CD threading, multiple oxygen coordination sites, π-electron rich fully conjugated framework, and the complementary nitrogen/cyano adsorption sites. Meanwhile, TPE-CD-COPR also showed excellent recyclability (99% capacity retention after 5 cycles). This groundbreaking synthetic strategy establishes a versatile platform for constructing polyrotaxane-based porous organic polymers (POPs) with tailored photophysical properties, and multifunctional adsorption capabilities, significantly expanding the application potential of porous materials in environmental remediation.