Redox-Induced Photoluminescence of Metal–Organic Coordination Polymer Gel

In this study, we have prepared a redox-active and intrinsically nonphotoluminescent metal–organic gel comprised of iron ions and terephthalic acid. In the presence of small reactive organic molecules like pyrrole, aniline, and bithiophene, the gelation process was unaffected and at the same time it led to the formation of highly photoluminescent hybrid materials. The photoluminescence turn-on response was primarily attributed to the redox reaction between iron ions and the small organic molecules generating oxidized oligomers in the porous gel matrix. A remarkable morphological transformation of the metal–organic gel from spindle-like to nanofibers, induced by the redox reaction, was detected. The adopted synthetic approach is very simple and the ease of tailor-making photoluminescence in the materials by varying the combinations of redox system and reactive small organic molecule will open up new perspective in the field of coordination polymers, specifically, for sensors, photonics, and photovoltaic applications.