Abstract
Porous magnesium-aluminium layered double hydroxides (LDH) were prepared through intercalation and decomposition of hydrogen peroxide (H2O2). This process generates oxygen gas nano-bubbles that pierce holes in the layered structure of the material by local pressure build-up. The decomposition of the peroxide can be triggered by microwave radiation or chemically by reaction with iodide (I−) ions. The carbonate LDH version [Mg0.80Al0.20(OH)2](CO3)0.1∙mH2O was synthesized by microwave-assisted urea coprecipitation and further modified by iodide or H2O2 intercalation. High resolution Scanning Electron Microscopy (HR-SEM) and Brunauer-Emmet-Teller (BET) analysis were used to assess the morphology and surface area of the new porous materials. The presence of H2O2 in the interlayer region and later decomposition triggered by microwave radiation generated more pores on the surface of the LDH platelets, increasing their specific surface area from initially 9 m2/g to a maximum of 67 m2/g. X-Ray Diffraction showed that the formation of the pores did not affect the remaining crystal structure, allowing possible further functionalization of the material.
Highlights
In this work we propose a method to increase the porosity of layered double hydroxides (LDH) compounds without pillarizing the interlayer region or use of toxic solvents, while avoiding the presence of residual chemical waste
Layered double hydroxides were synthesized by coprecipitation from a metal salt solution by means of microwave radiation
Microwave radiation allows the synthesis of crystalline LDH in relatively short reaction times
Summary
Porous magnesium-aluminium layered double hydroxides (LDH) were prepared through intercalation and decomposition of hydrogen peroxide (H2O2). This process generates oxygen gas nano-bubbles that pierce holes in the layered structure of the material by local pressure build-up. The dehydrated cold sample was immersed in 50 mL aqueous solution of 50 vol% H2O2 This suspension was cooled down to 5 °C to avoid premature decomposition of H2O2 and was stirred overnight to intercalate H2O2 in the interlayer space. The third procedure was based on the chemical reaction between H2O2 and iodide ions, but the starting compound was LDH-I, the iodide-intercalated form of this layered hydroxide (route B), see Fig. 1. LDH samples were degassed at 150 °C prior to the measurements
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