A wide variety of novel materials can be prepared through the chemical modification of silica gels. In addition to their use in chromatographic separations, they have been increasingly used as catalysts in liquid phase organic reactions. The application of these materials results in viable and more environmentally friendly alternatives to traditional homogeneous catalysts. The present monograph describes the synthesis of two functionalized silica gels for highly specific separation and preconcentration of metal ions followed by their applications as sensors and as catalysts.