Solvent-Induced Reversible Guest Uptake and Release by Flexible Porous Organic Cages

Porous organic cages with intrinsic and extrinsic cavities offer excellent host–guest control, molecular uptake, and on-demand release without compromising the selectivity. However, dynamic control over the porosity in cage molecules remains challenging. Herein, we report a CC3 cage-based crystalline adsorbent with dynamic control over its porosity for stable adsorption and release of the probe organic molecules. Interestingly, the polymorphic forms of cages (α and β) differ in crystallographic packing with flexible orientation but retain their structure after solvation. Using this isomorphism, the CC3 adsorbent exhibited an uptake of 29.5 mg g–1 for neutral red, 39.5 mg g–1 for methyl blue, and 39 mg g–1 for both molecules. The solvent-induced phase transition selectively obstructs neutral red adsorption with 85.5% change in overall capacity. Adsorption affinity correlates strongly with surface area, while solvent choice governs selectivity, highlighting switchable porosity. These findings enable advanced adsorbents with switchable porosity and selective affinity for energy and environmental applications.