Thiol-Functionalized Covalent Organic Framework for Efficient Metal Ion Removal in Water Treatment

Advanced water treatment technologies must offer selective, efficient, and cost-effective contaminant removal. In this study, TPB-DMTP-COF-SH, prepared from 1,3,5-tris(4-aminophenyl)benzene (TPB) and 2,5-dimethoxyterephaldehyde (DMTP), was synthesized via a two-step method and applied for the adsorption of aluminum (Al³⁺), iron (Fe²⁺), and manganese (Mn²⁺) ions from water. Adsorption performance was influenced by pH, initial concentration, and contact time, with optimal pH values of 3 for Al³⁺, 8 for Fe²⁺, and 10 for Mn²⁺. The adsorption data followed the Langmuir isotherm model, yielding maximum capacities of 3.27 mg g^-1 (Al³⁺), 8.5 mg g^-1 (Fe²⁺), and 0.67 mg g^-1 (Mn²⁺). Kinetic studies indicated a pseudo-second-order mechanism, suggesting chemisorption as the dominant process. Equilibrium adsorption was reached at 15 min for Al³⁺ and Mn²⁺ and 20 min for Fe²⁺. As a proof of concept, we demonstrate that this thiol-functionalized COF not only effectively removes metals but also offers enhanced processability into composite beads and membranes, making it a strong candidate for real-world water treatment applications. These findings highlight TPB-DMTP-COF-SH as a promising and scalable solution for water purification.