Synthesis of curtain-like crumpled boehmite and γ-alumina nanosheets

Boehmite (γ-AlOOH) nanosheets with a curtain-like crumpled morphology have been synthesized via a template-free hydrothermal process in two stages. The formation of the crumpled 2D nanostructures was studied at 70-95 °C in stage-1 and 150°C in stage-2 hydrothermal processes, and a growth mechanism was proposed. The introduction of corrugations and wrinkles prevents the nanosheets from severe interface stacking. Based on the XRD, TEM, and N₂ sorption analysis results, the thickness of the nanosheets is ca. 2.5-5 nm, which is composed of 2-4 lattice unit layers only. The crumpled boehmite nanosheets exhibit a high BET surface area of ca. 330 m² g^-1, and can be simply transformed into γ-Al₂O₃ with preservation of the morphology and ∼90% of the surface area after calcination.