Template-free fabrication of hierarchically meso/macroporous architecture of layered double hydroxide by dry gel conversion method

Abstract

A new type of hierarchically porous architecture of Mg2+, Al3+-containing layered double hydroxide, with well defined mesoporous/macroporous structure, has been fabricated by dry gel conversion method without the need of a surfactant and organic solvent. Predefined amorphous aluminum hydroxide gel and anhydrous magnesium sulfate were used as Al and Mg precursor material, respectively, and aqueous ammonia as precipitating agent. The resulting self-sustaining hierarchical layered double hydroxide material exhibits a bi-modal porous structure having a macroporous network with macropore sizes of 100–200 nm and a well defined mesoporous structure of pore size around 3.9 nm in the macroporous framework. Layered double hydroxide crystallites are aligned with a multilayer manner to form the architecture structure. The formation process of layered double hydroxide architecture, such as the evolution of phase composition, pore structure, and particle morphology with reaction time was further verified and the formation mechanism is postulated.