Structurally well-defined mesoporous silica materials, such as MCM-type silicas, 1 with tunable pore size and narrow pore-size distribution have attracted much attention for their potential applications in adsorption, catalysis, separation, and sensing. Organofunctionalized MCM-41 silica pores could serve as synthetic scaffolds to mimic enzyme or antibody active sites for specific covalent and/or noncovalent interactions with target molecules. 2 Herein, we report the design and synthesis of a fluorescence sensory system to study the molecular recognition events of biogenic molecules, such as dopamine and glucosamine, inside different functionalized mesoporous silica microenvironments.

Our design strategy took advantage of the size-sieving ability of the mesoporous silica framework as the supporting matrix to first incorporate an amine-sensitive o-phthalic hemithioacetal (OPTA) 3 group on the pore-surface. Only small molecules with amino groups can diffuse into the pores and react with the OPTA group to give rise to highly fluorescent isoindole products as depicted in Figure 1. In contrast to the molecular imprinted microand/or mesoporous silica materials4 where the selectivity was determined by the pore shape and the functional group density in each cavity, we prepared multifunctionalized pores to not only capture the target substrate molecules covalently but also provide different secondary noncovalent interactions. OPTA-derivatized mesoporous silica materials with various surface-bound functional groups allow modulation of our sensory system to enhance the substrate selectivity by tuning substrate accessibility and pore hydrophobicity.