The present invention provides a hexagonal mesoporous silica comprising a photo-dimerizable
organic functional group provided at the entrances of the pores thereof, and a
hexagonal mesoporous silica comprising a functional substance filled in the pores
thereof and a dimerized organic functional group provided at the entrances of the
pores to close the entrances. These hexagonal mesoporous silicas allow a substance
incorporated therein to be controllably released. The present invention also provides
a method of producing the mesoporous silica, and a method using the mesoporous
silica to control the release of a functional substance incorporated therein.