Hierarchical Porous MOF@LDH Core-Shell Structures As Efficient Adsorbent for Phosphate

Phosphate is a major water pollutant from agricultural fertilizers, industrial wastewater and household products. For practical removal of phosphate, adsorption at sources should be the one of the most important routes, which however needs high adsorptive efficiency. From the viewpoint of material engineering, the adsorbents require large surface area, high adsorption capacity, and strong bonding towards phosphate. Layered double hydroxides (LDHs) are a class of synthetic anionic clays and have been studied for various applications including as phosphate adsorbents, however the flake structures are easy to overlap, thus reducing the contact area of materials with pollutants. In this work, an aqueous stable metal organic framework (MOF) is used as supporter to vertically grow LDH on it, resulting in Hierarchical porous MOF@LDH Core-Shell structures. Based on the different characterization techniques, a growth mechanism of LDH on MOF is proposed. Various factors, such as pH, competitive anions, temperature, and zeta potential, were discussed. The adsorption capacity of as-synthesized core-shell composites enhances and the adsorption to reach 95% phosphate reduction decreases from 10-16min to 4-6min for high concentration (500ppm) of phosphate. The study provides novel insights into pollutant adsorptive removal and could be beneficial for inspiring functional composite material synthesis for environmental applications.