Green Synthesis of Low-Dimensional Aluminum Oxide Hydroxide and Oxide Using Liquid Metal Reaction Media: Ultrahigh Flux Membranes

Liquid metal reaction media provides exciting new avenues for synthesizing low-dimensional materials. Here, the synthesis of atomically thin sheets and nanofibers of boehmite (gamma-AlOOH) and their transformation into cubic alumina (gamma-Al2O3) via annealing is explored. The sheets are as thin as one orthorhombic boehmite unit cell. The addition of aluminum into a room temperature alloy of gallium, followed by exposing the melt to either liquid water or water vapor, allows growing either 2D sheets or 1D fibers, respectively. The isolated oxide hydroxides feature large surface areas, with the sheet morphologies also showing a high Young's modulus. The method is green, since the liquid metal solvent can be fully reused. The ultrathin boehmite sheets are found suitable for the development of freestanding membrane filters that enable excellent separation of heavy metal ions and oil from aqueous solutions at extraordinary filtrate flux. The developed liquid metal-based synthesis process offers a sustainable, green, and rapid method for synthesizing nanomorphologies of metal oxides which are challenging to obtain by conventional methods. The process is both sustainable and scalable and may be explored for the creation of other types of metal oxide compounds.