Calcium-Based Metal-Organic Framework: Detection and Idiosyncratic Removal of Copper by Nano-Particle Deposition

A novel calcium-based metal-organic framework (CaMOF@LSB) was designed and synthesized, exhibiting dual functionality for both selective detection and removal of Cu²⁺ ions from aqueous solutions. The framework's stability, including solvent and pH variations, was established with notable thermal resilience. Colorimetric Cu²⁺ detection (≥5 ppm) with a high capture capacity of 484.2 mg g^-1 by CaMOF@LSB places this material among the few that ensure efficient colorimetric detection and high removal capabilities of Cu²⁺ ions. Batch adsorption experiments revealed pH-dependent behavior and competitive interactions. Langmuir and pseudo-second-order kinetics models aptly described adsorption isotherms and kinetics, respectively. Thermodynamic assessments confirmed spontaneous and endothermic adsorption. Mechanistically, nanoparticle deposition contributes to the Cu²⁺ uptake. CaMOF@LSB also exhibited one of the best removal behaviour of Cu²⁺ by means of oxide formation on the surface. Regeneration of CaMOF@LSB was achieved by simple sonication in 0.1 M aqueous NaOH solution. The recyclability was also tested up to 5 cycles, and it exhibited a small decrease in adsorption capacity observed across the cycles. This research presents a promising avenue for addressing heavy metal pollution using metal-organic frameworks, thereby offering potential applications in water purification and environmental pollution monitoring and remediation.