Multi-imidazolium cage-like microspheres: Synergistic multi site hydrogen bonding and geometric confinement for selective 99TcO4−/ReO4− capture in harsh media

A cage-like multi-imidazolium sorbent is designed for 99 TcO 4 − /ReO 4 − capture. • Cooperative clamping in confined spaces enables ultrafast adsorption kinetics. • The sorbent exhibits a high ReO 4 − uptake capacity of 730 mg g −1 . • Excellent selectivity is achieved in highly competitive nuclear waste media. • Composite beads allow efficient fixed-bed removal with good regenerability. The efficient and selective removal of pertechnetate ( 99 TcO 4 − ) 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 ( 99 TcO 4 − )/perrhenate (ReO 4 − ) 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 ReO 4 − as a nonradioactive surrogate for 99 TcO 4 − , 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. Propeller-like TPE-based cage-like microspheres spatially organize multiple imidazolium sites into confined binding pockets, enabling cooperative multi-site clamping for rapid and selective ReO 4 − / 99 TcO 4 − capture through hydrogen bonding, electrostatic attraction, ion exchange, and hydrophobic confinement. Download: Download high-res image (184KB) Download: Download full-size image