Equisetum arvense Templating of Zeolite Beta Macrostructures with Hierarchical Porosity

Biomimetic zeolite Beta macrostructures with hierarchical porosity were prepared by using a silica-containing vegetal template (Equisetum arvense). Leaves and stems of Equisetum arvense were subjected to hydrothermal treatment with a zeolite Beta precursor solution. The zeolite readily crystallized in the vegetal tissues with the zeolite nucleation being induced by the highly reactive biomorphic silica deposited at the epidermal surface of the plant. Upon calcination the obtained zeolite/vegetal composite was transformed into a solely zeolite macrostructure that retained all morphological features of the vegetal template. The analysis of the zeolite/vegetal composite and all-zeolite replica showed that material with hierarchical porosity was obtained. The leaves and the stems of Equisetum arvense were transformed into micro-/mesoporous and micro-/meso/macroporous structures, respectively. These structures were built up of zeolite nanoparticles with smaller sizes compared to the crystals from the bulk solution. Thus, the biotemplate controlled both the macromorphology and the nanolevel organization of the materials.