6-Hydroxyquinoline is an ideal photoacid system for exploring excited-state proton transfer (ESPT) reactions. The excited-state proton transfer and geminate recombination of 6-hydroxyquinoline encaged in catalytic Na+-exchanged faujasite zeolites X and Y have been explored by measuring steady-state and picosecond time-resolved spectra.6-Hydroxyquinoline was used in synthesis of 2,6-substituted-benzo[d]thiazole analogs and 2,4-substituted-benzo[d]thiazole analogs. 6-Hydroxyquinoline is an ideal photoacid system for exploring excited-state proton transfer (ESPT) reactions. The excited-state proton transfer and geminate recombination of 6-hydroxyquinoline encaged in catalytic Na+-exchanged faujasite zeolites X and Y have been explored by measuring steady-state and picosecond time-resolved spectra. 6-Hydroxyquinoline was used in synthesis of 2,6-substituted-benzo[d]thiazole analogs and 2,4-substituted-benzo[d]thiazole analogs.