Synthesis and characterization of ordered mesoporous aluminosilicate molecular sieve from natural halloysite

• Hexagonally ordered mesoporous aluminosilicate molecular sieve has been synthesized successfully from natural halloysite without addition of silica or aluminum reagents.
• The BET surface area and pore volume of the prepared sample reached up to 524.6 m2/g and 0.87 cm3/g, respectively.
• 27Al solid state MAS NMR spectrum showed that all of aluminum species were tetrahedrally coordinated into the framework of the mesoporous material.
• A possible mechanism for the formation of mesoporous aluminosilicate molecular sieve from natural halloysite was discussed.

Currently, opening up the possibility of low-cost mineral for preparing ordered mesoporous materials is of significant importance. In the present work, hexagonally ordered mesoporous aluminosilicate molecular sieve was hydrothermally synthesized from natural halloysite without addition of silica or aluminum reagents. The mesoporous structure of the synthesized materials was confirmed by small angle X-ray diffraction and nitrogen sorption analysis. Scanning electron microscope and transmission electron microscope observations indicated that highly ordered two-dimensional hexagonal mesoporous structure was obtained. Wide angle X-ray diffraction and Fourier transform infrared spectroscopy were also used to examine the variations of chemical structures. The surface area of the prepared material after being calcined at 550 °C was 524.6 m2/g and the pore volume was 0.87 cm3/g. 27Al solid state magic angle spinning nuclear magnetic resonance spectrum showed that all of aluminum species were tetrahedrally coordinated into the framework of the mesoporous material. A possible mechanism for the formation of aluminosilicate molecular sieves from natural halloysite was also discussed accordingly.