Synthesis and Characterization of Tetraborate Pillared Hydrotalcite

Hydrothermal synthesis of tetraborate, B 4 O 5 (OH) 4 2 -, -pillared hydrotalcites was investigated, and an efficient way of preparing them was found. The structures of the pillared materials were characterized using a combination of techniques such as powder X-ray diffraction, FT-IR, 11 B and 27 Al MAS NMR, DTA/TGA, and chemical analysis. The results show that the structure of the coprecipitate is important in controlling the formation of B 4 O 5 (OH) 4 2 - -pillared hydrotalcites. With a slurrylike precipitate, a more ordered structure of the pillared hydrotalcite is obtained, while with a wet cakelike precipitate, a disordered structure of the pillared hydrotalcite is formed. The tetraborate anions in the interlayer space orient with their tetrahedral BO 4 linkage perpendicular to the sheets of hydrotalcite. The tetraborate pillared material has a chemical composition of [Mg 0.70 Al 0.30 (OH) 2 ][B 4 O 5 (OH) 4 ] 0.15 ·H 2 O and a surface area of ∼47 m 2 /g.