Applications of layered double hydroxide nanomaterials in environmental remediation: Synthesis, structural modification and performance enhancement

Layered double hydroxides (LDHs) are a type of two-dimensional layered semiconductor nanomaterials with unique characteristics such as acidic and alkaline characteristics, memory effect, exchangeability of interlayer anions, and microporous structure, which have widely been used in the fields of water splitting, CO2 2 reduction, heavy metals removal, degradation of organic pollutants, and air pollution control. However, the original LDHs still face challenges such as a narrow light absorption range, weak pollutant adsorption ability, slow charge carrier separation-migration, low catalytic efficiency, and poor structural stability in practical applications. To address these technical bottlenecks, structural modification strategies have been widely investigated to expand the application prospects of LDH-based catalysts for environmental remediation. Here, we review the characterization and modification engineering of LDH-based nanomaterials to enhance their physicochemical properties for application in environmental catalysis. In particular, recent advances in their applications for CO2 2 reduction, photocatalytic nitrogen oxides (NOx) removal, catalytic degradation of volatile organic compounds (VOCs), and selective catalytic reduction of NOx are systematically presented. The structural modulation of LDHbased nanomaterials on the band structure, electronic properties, and carrier dynamics are discussed in detail to reveal the mechanism of the structural design on the catalytic performance. This review also emphasizes the key role of LDH-based catalysts in advancing environmental remediation and looks forward to the prospects and opportunities for the engineering development of rationally designed LDH-based catalysts that can be applied to environmental remediation with green, highly efficient, and stable performance, opening up a new route in this frontier research.