Multivariate Sulfur-Functionalized MOFs Shaped into Alginate Spheres for Robust and Reusable Multidye Water Remediation

Abstract

The removal of synthetic organic dyes from contaminated water remains a major environmental challenge, particularly under multicomponent and real-water conditions. Herein, we report a scalable adsorption platform based on sulfurfunctionalized metal-organic frameworks (MOFs) for efficient multidye removal. Three isoreticular MOFs, including a multivariate analogue incorporating methylcysteine and methionine functionalities, were evaluated using real water (Turia River, Spain). The multivariate MOF shows faster adsorption kinetics and achieves quantitative dye removal, outperforming its monofunctional counterparts. For practical implementation, the MOFs were immobilized into calcium alginate spherical beads (≈50 wt% loading), yielding mechanically robust composites that preserve crystallinity and porosity. The shaped materials retain high adsorption efficiency and can be reused over multiple cycles without performance loss. Under continuous-flow solid-phase extraction conditions, the system achieves >99% removal for all dyes, enabling rapid and effective water decontamination.