A facile route for the flowerlike Mg7B4O13 · 7H2O nanostuctures: Synthesis, growth mechanism and thermal treatment

• Flowerlike Mg7B4O13 · 7H2O were obtained via precipitation method assisted with PVP.
• The possible growth mechanism for the flowerlike nanostructure was proposed.
• Porous Mg3B2O6 with large specific surface areas was obtained after thermal treatment.

In the presence of the surfactant poly(vinyl pyrrolidone) (PVP), 3D hierarchical flower-shaped Mg7B4O13 · 7H2O nanostructures were synthesized via a facile precipitation process using Mg(NO3)2 · 6H2O and Na2B4O7 · 10H2O as the raw materials. The nanostructures with diameters of 0.8–1.2 μm are composed of numerous polycrystalline nanosheets with thickness of about 10 nm. The possible growth mechanism for the flower-shaped nanostructures was proposed based on the systematic structural and property characterizations including XRD, SEM, TEM, IR and N2 adsorption–desorption. The phase transformation can be observed during the calcination process, and the flower-shaped nanostructures can be successfully maintained after calcination at 550 °C and 650 °C. The adsorption–desorption experiments show the appearance of mesopores before and after calcination co-existed with small amount of macropores. The highest surface area of 111 m2/g and largest pore volume of 0.37 cm3/g are obtained in these hierarchical porous Mg3B2O6 nanoflowers. These novel porous borate-based materials could be applied in drug delivery, catalysis, environmental abatement, energy storage, etc.

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