Selective Removal of Purines from Aqueous Solution Using Cucurbit[N]Uril: A Comprehensive Review

Abstract

Purine bases and their metabolites, including adenine, guanine, xanthine, hypoxanthine, uric acid, and methylxanthines such as caffeine, are essential biological compounds that have increasingly emerged as environmentally relevant micropollutants due to widespread human consumption and their incomplete removal by conventional wastewater treatment processes. Their high water solubility, structural similarity, and persistence at trace concentrations in complex aqueous matrices make selective removal particularly challenging. This review examines the sources, environmental significance, chemical behavior, and health implications of purines in aquatic systems, while critically assessing the limitations of existing treatment technologies such as conventional adsorption, membrane filtration, biological degradation, and advanced oxidation processes, which often suffer from poor selectivity, high energy demand, fouling, or incomplete mineralization. Emphasis is placed on cucurbit[n]urils (Q[n]) as a promising supramolecular platform for the selective removal of purines from water. The unique molecular architecture of Q[n], characterized by hydrophobic cavities and carbonyl-lined portals, enables highly specific host–guest interactions driven by size complementarity, hydrophobic inclusion, hydrogen bonding, and ion–dipole interactions. The review highlights the influence of cucurbituril ring size on purine selectivity, competitive binding behavior in multicomponent systems, and the advantages of nonporous adaptive crystals for selective uptake under realistic conditions. Current challenges related to scalability, material stability, and process integration are discussed, alongside future perspectives for the rational design of next-generation Q[n]-based adsorbents. Overall, this work underscores the potential of cucurbituril-based supramolecular systems as precision-engineered tools for sustainable purine management in environmental and biomedical applications.