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.