Ethenylene groups within the silicate framework of hybrid mesoporous ethenylene-silica (HME) are successfully modified via a two-step chemical modification process (see Figure) to produce a sulfonic acid-functionalized hybrid mesoporous solid acid catalyst. The material exhibits high activity for various acid-catalyzed reactions and can be used repeatedly without deactivation. The Diels-Alder modification described can be extended to the creation of other functional materials.