The infrared spectra were recorded using a Fourier transform
infrared (FTIR) spectrophotometer (FTIR 8400s, Shimadzu). The Xray
diffraction (XRD) patterns of the samples were obtained with an
X-ray diffractometer (X’Pert, Philips). The weight loss of the porous
silica was studied using thermo gravimetric and differential thermal
analysis (TG-DTA, Shimadzu) in air from room temperature to
1000 ◦C.