Modulating the surface microenvironment of supramolecular frameworks to achieve selective and recyclable adsorption of dyes in water

Abstract

Supramolecular frameworks (SMFs) are famous for their fascinating structure and abundant porosity; however, poor crystalline stability in water severely limits their applications. Herein, an anchoring-polymerization strategy was developed under mild conditions to modulate the surface microenvironment of SMFs. The process-tracking experiment demonstrated that toluene diisocyanate (TDI) was anchored on the surface of SMF-BDC-NH₂ before chain polymerization was initiated between TDI by introducing trace amounts of water. The glue-like polyurea armor on the surface of SMF-BDC-NH₂@PTDI endowed it with a water contact angle of 131.3°, and it can maintain good crystallinity and a porous structure even when immersed in water for 24 hours. SMF-BDC-NH₂@PTDI was proved to selectively adsorb cationic dyes, and no significant loss was detected after 5 runs, whereas the pristine material lost crystallinity and adsorption performance immediately after regeneration. The dynamic breakthrough experiment showed that SMF-BDC-NH₂@PTDI had an adsorption capacity of 124 mg g⁻¹, positioning it among the best materials of its kind. Suitable pore size and charge interactions are proved to be the main driving forces for selective adsorption. This work may open a path to modulation of the surface microenvironment of SMFs to maintain crystalline stability and enable advanced applications in water treatment.