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.