Improving Stability, Crystallinity, and Photo-Responsiveness of Supramolecular Frameworks by Surface Polymerization

Metal–organic cage-based photo-responsive supramolecular frameworks (PSMFs) with permanent porosity have gained attention for their modular properties, controllable functionality, and light-induced reversible responsiveness. However, their high porosity and photo-responsive efficiency are often compromised due to poor structural stability upon solvent removal, limiting their potential applications. Here, a solution to overcome this challenge by employing a surface polymerization strategy using isophorone diisocyanate (IDI) to stabilize PSMF (PCC-20t) is presented. This approach results in the composite of PCC-20t@PolyIDI, which preserves crystallinity and permanent high-porosity while avoiding structural collapse commonly observed in highly porous supramolecular frameworks. Moreover, compared to activated PCC-20t, PCC-20t@PolyIDI exhibits an 18.6-fold increase in specific surface area. Remarkably, the structural variability of PCC-20t@PolyIDI can be observed in the photo-regulation behavior of CO₂ capacity under the irradiation of vis- and UV-light, showing a 27.9% change in adsorption amount for CO₂ which is significantly higher than that of the activated PCC-20t with 7.0% for CO₂. Grand Canonical Monte Carlo simulations demonstrate the light-regulated adsorption performance is attributed to the configuration transformation of azobenzene from trans- to buckling state. The findings may pave the way for stabilizing high-porosity materials to simultaneously meet demands for high-porosity and photo-responsive efficiency.