Novel COF-based core–shell material UiO@BTT–BPDA as an adsorbent for efficient and rapid removal of persistent organic pollutants

Abstract

Covalent organic frameworks (COFs) frequently encounter issues like low crystallinity and high hydrophobicity, hindering their application in water purification. This research synthesized two new COF materials (BTT–BPDA) using benzothiophene tricarboxaldehyde (BTT) and [2,2′-bipyridine]-5,5′-diamine (BPDA) as building blocks, which showed strong adsorption capabilities for dye molecules. To improve crystallinity and adsorption, BTT–BPDA-COF was grown on UiO-66, creating two core–shell composites. The individual MOF and COF materials were surpassed in adsorption performance by these composites. This enhancement can be attributed to a decrease in hydrophobicity, an increase in hydrophilicity, and the provision of extra adsorption sites facilitated by hydrogen bonding and π–π stacking interactions. Remarkably, the UiO-66-NH₂@BTT–BPDA composites attained maximum adsorption capacities of 1001.3 mg g⁻¹ for Congo red, 1616.8 mg g⁻¹ for Rhodamine B, and 1837.3 mg g⁻¹ for Malachite green, underscoring their effectiveness in addressing dye-polluted wastewater.