Comprehensive insights into anionic layered materials: Assembly, synthesis, reactivity, and application paradigms

During recent times, the study of two-dimensional anionic layered materials (ALMs) has become an area of significant research. ALMs exhibit a wide spectrum of structural characteristics involving simple exchange of anions within the interlayer region, i.e., anion-exchange as well as the intercalation of various complex guest species, enabling control over chemical composition and surface functionalities. The present review comprehensively summarizes the synthesis of layered double hydroxides and their derivatives via conventional and novel synthetic methodologies for enhancing the physical, chemical, optical, and catalytic properties of layered materials. Further, a detailed overview of the structural chemistry, compositional flexibility, anion exchange behaviour, surface modification, topotactic transformation, and colloidal stability that act as key attributes for governing their functional performance and adaptability in diverse applications has also been discussed. The review further highlights the integral role of advanced spectroscopic and microscopic techniques-including powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), and electron microscopy-in elucidating the layered framework and verifying intercalation phenomena. The applications of ALMs across diverse fields, including water remediation, ceramics, biomedicine, antimicrobial agents, biosensing, and display technologies have also been critically examined. We believe that this review holds immense potential to deepen the understanding of structural chemistry, properties, and applications of ALMs, underscoring their promising role in sustainable technology development and advanced functional materials.