Construction of Layered Double Hydroxides from Bottom Chemical Manipulation up to Applications—A Comprehensive Review

Layered double hydroxides (LDHs) are functional anionic clays that belong to the family of two-dimensional (2D) materials. LDHs consist of positively charged brucite host layers separated by guest-exchangeable interlayer anions, which overall offer unique chemistry like flexible metal composition, ion-exchange capability, and structural reconstruction through memory effect property. These features provide exceptional opportunities for modulating the surface chemistry of LDHs through bottom-up synthetic strategies. By controlling chemical environment conditions and employing appropriate modulating agents, it is feasible to engineer morphology, introduce local structural imperfections such as oxygen and metal vacancies (Schottky defects), generate unsaturated coordination sites, and incorporate heteroatoms to enhance functionality. This review aims to examine recent advances in the chemical modulation and morphological control of LDHs. We summarize the principal bottom-up synthetic approaches and discuss how chemical doping, host–guest interactions, and defect engineering can be employed to tailor the structure and properties of LDHs. In particular, we emphasize the relationship between chemical modulation, morphology, and functional performance in environmental and energy-related applications. Specifically, we highlight recent progress in pollutant adsorption, degradation of organic contaminants, and hydrogen production, providing insights into the design of next-generation LDH-based materials for sustainable environmental and energy technologies.