Six mesoporous materials functionalized with amine groups were developed and screened as potential supports for chloroperoxidase (CPO). A periodic mesoporous organosilane (PMO PA-40) with pore entrances large enough to allow the enzyme entry inside the pores was found to be the best support. When CPO was immobilized onto this material, it could be reused 20 times with retention of activity. On materials with little mesoporous structure and/or pore entrances too narrow to allow the enzyme entry to the channels, immobilized CPO rapidly lost activity upon reuse. Similarly, postsynthetic amino functionalization of a pure silica mesoporous material did not yield a stable biocatalyst.