Functionalized Periodic Mesoporous Organosilicas: From Metal Free Catalysis to Sensing
In this work a widely usable post-modification route for Periodic Mesoporous Organosilicas (PMOs) was developed. Using the developed method, two diverse ligands, picolinic acid (Pic) and 4,4',4'',4'''-porphyrin-5,10,15,20-tetrayltetrabenzoic acid (Porph), were successfully covalently coupled onto the PMO material and well characterized. Both obtained materials still show high BET surface areas (565 m2/g for Pic@PMO, 483 m2/g for Porph@PMO and 548 m2/g for the unmodified PMO) and pore size (5.1 nm). The materials were subsequently tested for their catalytic activity in the cycloaddition of epoxide and CO2, a frequently studied carbon capture and utilization reaction. Interestingly, both materials showed very good reactivity (with conversions up to 90%) as metal free heterogeneous catalysts and proved to be perfectly stable in recyclability and aging tests. Moreover, by (co-)grafting Eu3+ and Tb3+ ions onto Pic@PMO and Yb3+ ions onto Porph@PMO strong emission was observed in the visible and near-infrared (NIR) range, respectively. Eu,Tb@Pic@PMO showed potential for use as a temperature sensor in the physiological range (a maximum Sr value of 2.11 %K-1 was obtained at 273 K), while Yb@Porph@PMO could efficiently be excited within the human tissue penetrat-ing window showing characteristic Yb3+ luminescence (with decay times around 10 μs). These findings prove that simple modifications of this PMO can provide smart materials for very diverse applications.
- This article is part of the themed collection: 2019 Journal of Materials Chemistry A HOT Papers