Hydrothermal Synthesis and Crystallization Mechanism of a Novel Microporous Phosphate with Submicron Holes

Microporous phosphate crystals with submicron holes, HAP-TAP, was hydrothermally prepared. HAP-TAP is composed of two different crystals, the hexagonal prism crystals and the layer crystals. Its morphology was characterized by abundant submicron holes (0.4–0.8 μm) distributing on the surface of hexagonal prism crystals and the layer crystals growing in the holes. The process of crystallization was investigated by scanning electron microscopy, powder X-ray diffraction (XRD), infrared spectroscopy, and energy dispersive X-ray (EDX) spectroscopy. The hexagonal prism single-crystal HAP was obtained by adjusting the crystallization time. The single-crystal XRD results showed that HAP is a novel microporous aluminum phosphate with a formula of Al5(OH)2(PO4)7-(C2N2H10)3·0.5H2O and two-dimensional open-framework structure. EDX results showed that the layer crystals located in submicron holes were titanic aluminum phosphates.