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A bioinspired calix[4]trap ion container, representing a novel kinetically gated supramolecular host, was developed for programmable ammonium sequestration and release. Cs + preferentially binds at the crown‐6 modified entrance to act as a removable physical gatekeeper, which successfully restricts cavity access for NH 4 + and decouples the ion release kinetics from the thermodynamic driving force. More details are discussed in the article by Zhu et al . on pages 3099—3105. image