Synthesis and characterization of large-pore FDU-12 silica

Large-pore FDU-12 (LP-FDU-12) silicas with face-centered cubic structures of spherical mesopores of diameter 16-26 nm were synthesized using Pluronic F 127 triblock copolymer template. The materials were characterized using small-angle X-ray scattering and nitrogen adsorption. The initial temperature range suitable for LP-FDU-12 synthesis was shown to be much wider than that reported earlier (7-15 degrees C vs. 14-15 degrees C). However, the degree of structural ordering was lower and the pore size distribution was broader in case of temperatures of 7-9 degrees C. The removal of the template by calcination resulted in a significant shrinkage (unit-cell parameter decrease by 10-16%) and afforded samples with low adsorption capacity, unless the synthesis involved a hydrothermal treatment in an HCl solution, which reduced the shrinkage and significantly increased the pore volume. The selection of time and temperature of the acid treatment allowed us to adjust the pore diameter of LP-FDU-12. However, the broadening of pore size distribution was observed for excessively long treatments at 130 degrees C. The treatment at 130 degrees C allowed us to tailor the pore entrance size in LP-FDU-12. (c) 2007 Elsevier Inc. All rights reserved.