Synthesis of a Crystalline and Transparent Aerogel Composed of Ni–Al Layered Double Hydroxide Nanoparticles through Crystallization from Amorphous Hydrogel

Abstract

Enormous efforts have been devoted to the development of crystalline aerogels toward heterogeneous catalysis, energy storage, ion/ molecular absorption, and luminescence. However, properties of aerogels are not fully exploited due to their low content of functional moieties embedded in their solid networks, low crystallinity, and limited chemical compositions. Herein, we develop a one-pot approach based on crystallization from amorphous metal hydroxides modified with a β-diketone ligand, toward crystalline transition-metal hydroxide aerogels. Synthesis of monolithic and crystalline aerogels of layered double hydroxide (LDH) was performed in a Ni−Al system starting from aqueous ethanol solutions of NiCl 2 •6H 2 O and AlCl 3 •6H 2 O with acetylacetone (acac) as an organic ligand. Propylene oxide (PO) as an alkalization reagent was added into precursory solutions to yield monolithic wet gels. The successive pH increase induces the formation of a threedimensional (3-D) solid framework composed of amorphous Al(OH) 3 . Then, amphoteric Al(OH) 3 undergoes crystallization into Ni−Al LDH via an acetylacetone-driven dissolution−crystallization of metal hydroxides without destroying the preformed 3-D solid framework. The process allows us to obtain crystalline aerogel monoliths with high porosity and high transparency after supercritical CO 2 drying of wet gels. The present scheme can be expected to synthesize functionalized aerogel composed of crystalline transitionmetal oxide/hydroxide nanobuilding blocks (NBBs).

A facile, green and scalable approach to fabricate hierarchical ZnAl-LDH for efficient removal of hexavalent chromium

“…5a), in which the broad peak appearing at 211 represents the characteristic feature of amorphous Al(OH) 3 . 54,55 Therefore, based on the above results, it is reasonable to propose that the hydroxyl groups play a critical role in the sorption performance of ZnAl-LDH-D toward Cr VI via complexation, replacement, and reduction.…”

Processing porous architectures based on LDH: Synthesis and novel applications

“…3). (Takemoto et al, 2020b) The relatively large pores (43.6 nm) are formed as a result of the formation of a network of secondary particles. Reproduced from Ref.…”

Morphology and size control of an amorphous conjugated polymer network containing quinone and pyrrole moieties via precipitation polymerization

“…In previous studies, isotropic morphologies were obtained by the conversion of spherical amorphous precursors. 31,32 As another method, the rapid reaction and precipitation of the layered metal oxides provided the nanoparticles with the inhibition of the growth. [33][34][35][36] The results imply that the nucleation burst at the initial stage of the reaction in the solution phase can form spherical nanoparticles even with the intrinsically anisotropic structures.…”