Reconfigurable Mechanically Interlocked Metal–Organic Nanocages for Adaptive Guest Recognition and Allosteric Regulation

Replicating the allosteric regulation of biological systems in synthetic nanostructures remains a fundamental challenge in supramolecular chemistry. Here, we report a reconfigurable Pd2L4 nanocage (Ex-MC) that undergoes thermally triggered mechanical interlocking to form a Pd4L8 dimer (I-Ex-MC), establishing a versatile platform for stimuli-responsive molecular recognition at the nanoscale. Utilizing electrostatic interactions and the dynamic adaptability of the triphenylamine (TPA) scaffold, Ex-MC achieves exceptional selectivity for sulfonate anions (up to 380-fold) through an induced-fit mechanism reminiscent of enzyme–substrate recognition. Crucially, the monomer–dimer interconversion is fully reversible via temperature modulation or acid/base stimuli, as demonstrated by thermodynamic analysis (ΔH = 36.6 kJ mol–1, ΔS = 105.5 J mol–1 K–1). Furthermore, the encapsulation of ReO4– within I-Ex-MC induces a pronounced allosteric response, expanding the central cavity while compressing the peripheral chambers, a behavior reminiscent of cooperative binding in biological receptors. This work establishes mechanical interlocking as a powerful strategy for engineering adaptive nanoarchitectures with potential applications in selective sensing, molecular separation, and intelligent nanomachinery.