Recent advances in layered double hydroxides (LDHs) as two-dimensional membrane materials for gas and liquid separations

Membrane-based technology represents an emerging strategy for energy-efficient gas/liquid separation. Among various factors, dimensionality and microstructure of membrane materials played a dominant role in determining their separation performance. Recently, unique structural properties of two-dimensional (2D) nano-materials with atomic size thickness are rapidly emerging as desirable building blocks for the design of high performance membranes. Among them, layered double hydroxides (LDHs), a representative of anionic clays, have attracted extensive interest and exhibited promising prospects for membrane applications due to their uniform interlayer galleries, which may permit precise molecular sieving in case the gallery height was comparable with kinetic diameters of guest molecules. Moreover, highly tunable chemical compositions and gallery height as well as the rich surface functionality of LDH building blocks further endowed them with unprecedented opportunities for efficient gas/liquid separation. This paper summarizes recent breakthrough in LDH-based separation membranes with particular emphasis on the opportunities and challenges facing their commercial applications.