Pillararene-Based Aggregation-Induced-Emission-Active Supramolecular System for Simultaneous Detection and Removal of Mercury(II) in Water.

Supramolecular polymers are polymers based on monomeric units held together with directional and reversible noncovalent interactions. Compared with traditional polymers, they possess better processability and better recycling properties, owing to their reversible monomer-to-polymer transition. Herein, we report the construction of a new supramolecular system through self-assembly of a thymine-substituted copillar[5]arene 1 and a tetraphenylethylene (TPE) derivative 2 in the presence of Hg. Copillar[5]arene 1 can coordinate with Hg tightly through T-Hg-T pairings. On the other hand, 1 can bind with guest molecule 2 through host-guest interactions between the pillararene cavity and the nitrile moiety of 2. These joint interactions generate crisscrossed networks composed of 1, 2, and Hg, which eventually wrap into spherical nanoparticles. Due to the aggregation-induced emission (AIE) properties of 2, the formed supramolecular polymer exhibits strong fluorescence which renders convenient the detection of the Hg-containing nanoparticles and the subsequent removal procedure. Furthermore, the polymer precipitate can be readily isolated by simple treatment, and the pseudorotaxane 2 ⊂ 1 can be recycled and reused. Our study has demonstrated a practical strategy for the sensing and removal of heavy metal ions in water by the construction of supramolecular polymers.