Mesopore walls of hierarchically meso-/microporous zeolites (MFI, BEA and LTA) are covered with silanol groups, so that the zeolites can be functionalized with various organic groups via silylation; the organic-functionalized hierarchical zeolites exhibit hydrothermal stability and reusability in catalytic applications, as compared with organic-functionalized mesoporous silica. ; This work was supported by the National Honor Scientist Program of the Ministry of Education, Science and Technology in Korea.