Multi-imidazolium cage-like microspheres: Synergistic multi site hydrogen bonding and geometric confinement for...

The efficient and selective removal of pertechnetate (⁹⁹TcO₄^-) from water remains a significant challenge due to its high solubility, low charge density, and competition from coexisting anions. Herein, we report tetraphenylethene (TPE)-based, imidazolium-functionalized nanomicrospheres for pertechnetate (⁹⁹TcO₄^-)/perrhenate (ReO₄^-) capture with high efficiency. The nonplanar, propeller-like TPE core stereospecifically arranges multiple imidazolium sites in a semi-encapsulating/polyhedral fashion, generating size-complementary pockets. Hierarchically confined nano-spaces enable cooperative multi-imidazolium clamping, where hydrophobic effects, electrostatic attraction, ion exchange, multipoint C-H···O hydrogen bonding, and geometric confinement act in concert to afford precise recognition and strong binding. Using ReO₄^- as a nonradioactive surrogate for ⁹⁹TcO₄^-, the sorbent delivers ultrafast kinetics (11.23 g mg^-1 min^-1), high capacity (730 mg g^-1), and 86.5% removal from Hanford low-activity waste (LAW) stream. The powder is readily formed into mechanically robust granules and shows excellent regenerability in fixed-bed tests, retaining >95% efficiency after multiple cycles. This work demonstrates that cooperative multi-imidazolium clamping within confined nano-spaces amplifies multimechanism synergy, providing a general strategy for precise recognition and strong binding of weakly coordinating anions.