Isolation and Stabilization of LDH 2D Crystals with Ultrahigh Surface Exposure via Polymer Gel Formation

Abstract A large specific surface area is one of the most attractive features of 2D crystals. However, the surfaces/interfaces of the 2D crystals of delaminated layered double hydroxides (LDHs) cannot be efficiently utilized because they are naturally unstable, and their surfaces cannot be highly exposed using current isolation methods. This study proposes a new strategy in this work to isolate LDH 2D crystals with large surface exposure by forming polymer gels. The gels are synthesized by combining ZnAl‐LDH unilamellae with acrylic acid anions (AA⁻) in delaminating solvent and mixing the solution with acrylamide (AAm) monomers for in situ copolymerization. The results show that the AA⁻ inhibits the dissolution of the unilamellae in formamide and that the polymer chains fix the unilamellae in the gel network. This stabilization effect results from the anchoring bonds of the COO⁻ groups with the LDH layer. It is found that the AA⁻‐containing gels without LDH have adsorptivity toward phosphate, whereas the poly‐AAm gel possesses hardly any adsorptivity. The nanocomposite hydrogels show phosphate adsorption amounts close to the theoretical values calculated according to the contents of AA⁻ and LDH. This implies that nearly all the unilamellar LDH surfaces are exposed to phosphate.