Alginate- and chitosan-based metal–organic framework biocomposites for adsorptive removal of heavy metals, dyes, and emerging contaminants: a comprehensive review

The progressive deterioration of aquatic systems due to the accumulation of chemically diverse and persistent contaminants constitutes a critical environmental challenge. Toxic pollutants, including heavy metals, synthetic dyes, and pharmaceutical residues, are increasingly accompanied by emerging contaminants such as endocrine-disrupting compounds, per- and polyfluoroalkyl substances (PFAS), and microplastics, which exhibit high chemical stability, bioaccumulation potential, and resistance to conventional treatment processes. Existing remediation technologies remain inadequate for their efficient removal, particularly at trace concentrations and within complex aqueous matrices. Metal–organic frameworks (MOFs), owing to their high surface area, tunable porosity, and versatile coordination chemistry, have attracted significant attention as advanced adsorbents; however, their practical application is hindered by hydrolytic instability, particle aggregation, and limited recyclability. This review systematically examines recent advances in MOF–biopolymer composites, with particular emphasis on alginate- and chitosan-based systems. Fabrication strategies, interfacial interactions, adsorption mechanisms, and structure–performance relationships are critically analysed across multiple pollutant classes. This work provides a rational, chemistry-oriented framework for the design and optimisation of sustainable MOF–biopolymer composites for advanced water purification applications.