Cation exchange reversibly switches rotor speed and is monitored by a networked fluorescent reporter.

Framework 1, a freely rotating turnstile, is transformed by sequential metal ion addition into the coordination-based double-minimum rotors [M2(1)]2n+ that operate at 8 kHz (M = Zn2+; n = 2) and 30 kHz (M = Cu+; n = 1). In a network with the fluorescent receptor 2, the metal ion exchange at [M2(1)]2n+ and thus indirectly the rotor speed is reported by distinct fluorescence changes at 2.