Controllable fluorescence via tuning the m-substituents of added aromatic molecules in a pyrene derivative-decorated porous skeleton

A novel pyrene derivative based composite fluorescent material was developed by immobilizing the pyrene-1-carboxylic acid (PyCOOH) into the pores of porous polyurea microspheres (denoted as PyCOOH-decorated PPUM). Encouragingly, the fluorescence spectrum of this synthesized composite microsphere only exhibited monomer emission of guest PyCOOH, indicating that the porous skeleton PPUM has excellent isolation ability to separate the guest molecules from each other. This discovery will provide an effective strategy to design and synthesize pyrene based host–guest systems without excimer emission. Notably, the PyCOOH-decorated PPUM can keep good fluorescent stability when dispersed in many organic solvents. More excitingly, it was found for the first time that the fluorescence of such a material can be regulated by adding aromatic compounds containing different m-substituted groups. When m-cresol was added, the intensity of the monomer emission enhanced significantly due to the unusual dissolution of the host porous polyurea sphere. By adding the m-toluidine, the monomer emission without the fluorescence of unassociated PyCOOH increased owing to the connection of m-toluidine and PyCOOH which escaped from the pores. In the presence of m-methylacetophenone and m-toluic acid, the monomer emission showing different degrees of decline was observed respectively because of the different substitution process. This result will contribute to the exploration of more promising candidates for pyrene-based fluorescent sensors.