Structural Symmetry in Advanced Materials for Wastewater Treatment: A Comprehensive Review

Structural symmetry is increasingly explored as a design concept in advanced materials for wastewater treatment, though its definition and practical relevance remain unclear. This review provides a critical overview of how symmetry (including crystallographic, pore-network, active-site, and architectural symmetry) affects pollutant removal. Representative material systems such as adsorbents, catalysts, and mixed-matrix membranes are examined for the removal of typical pollutants, including dyes, heavy metals, pharmaceuticals, and emerging contaminants. Symmetry is linked to improved transport uniformity, enhanced charge-carrier migration, facet-dependent reactivity in catalysts, and increased stability during cyclic operation. Symmetric architectures are compared with asymmetric and defect-rich designs, highlighting cases where asymmetry outperforms, particularly in complex matrices dominated by surface chemistry or kinetic accessibility. Performance metrics are discussed in their experimental contexts, with emphasis on qualitative structure–performance relationships. Environmental and economic implications are addressed qualitatively, focusing on life-cycle considerations, cost trends, scalability, and industrial feasibility rather than comprehensive techno-economic analyses. This review highlights when symmetry is beneficial, when its influence is limited, and how combining symmetry with asymmetry or defect engineering can lead to more practical wastewater treatment solutions.