A Rationally Designed NH4+ Receptor Based on Cation–π Interaction and Hydrogen Bonding

A cage-type receptor binds an NH4+ ion by cation-π interactions and hydrogen bonding with high sensitivity and selectivity, comparable or even superior to those of the natural antibiotic nonactin over a wide pH range. The high performance, low cost, and easy synthesis may offer practical applications for this receptor as an ammonium ion sensor.