Synthesis of phosphazene-covalent organic framework (cof) for enhanced lead capture with visual feedback

Abstract

There is disclosed a nitrogen-phosphazene-based covalent organic framework (PT-COF) designed for the effective and selective removal of lead (Pb2+) ions from aqueous solutions. Synthesized via a solvothermal method using hexa(4-formyl-phenoxy)cyclotriphosphazene aldehyde and 1,3,5-tris-(4-aminophenyl)triazine, the PT-COF exhibits an unprecedented adsorption capacity of 940 mg/g and reaches adsorption equilibrium within 20 minutes. The PT-COF demonstrates exceptional selectivity for Pb2+ ions over other heavy metals and provides a visual feedback mechanism, transitioning from yellow to dark brown upon lead adsorption, reverting to yellow upon desorption with acid treatment. The synthesis method yields a mesoporous material with high thermal and chemical stability, maintaining its crystalline structure under harsh conditions. The chemisorptive adsorption of lead (Pb2+) ions follows a pseudo-second-order kinetic model, fitting well into the Langmuir isotherm. This disclosure encompasses both the PT-COF product and the method for its synthesis, offering a sustainable and economically viable solution for lead remediation and water purification.

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