Physicochemical effects of amino- or sulfur-functional groups onto SBA-15 sol-gel synthesized mesoporous ceramic material

Abstract

SBA-15 mesoporous ceramics were synthesized by a sol-gel method with some modifications and functionalized with ethylenediamine or tetrasulfide groups and using a sequential washing approach of organic solvent mixtures. The effects of the functional groups onto the physicochemical properties were characterized using XRD, TG/DTA, FTIR, N2 adsorption–desorption, TEM, SEM and NMR. These analyses showed that the SBA-15 ceramic synthesized at low temperature shows a flat two-dimensional hexagonal symmetry with pore diameters of 7.1 to 7.8 nm. In the meantime, the functionalized ethylenediamine SBA-15 presented a narrow pore-size distribution with diameter around 3.5 to 5.7 nm. A different behavior was observed on the tetrasulfide SBA-15 showing a decrease in unit-cell parameter, in pore size (∼ 2.5 nm) and an increase in pore wall size with loss in structural order and at high sulfur concentrations exhibited an amorphous structure. Results indicated that the lattice crystalline structure value of the SBA-15 increased due to the amino-functionalization process to a value of 13.48 nm respect to a value of 12.72 nm in SBA-15 and decreased to 10.12 nm as an effect of the sulfur-functionalization process, indicative of the effect of the amino and sulfur group into the well-ordered hexagonal mesoporous structure of SBA-15 ceramic materials.