Guest-Enhanced Charge Separation in Porphyrin-Based Double-Cavity Metallacages for Visible-Light-Driven H₂O₂ Production

Hydrogen peroxide (H₂O₂) is a versatile and green oxidant with wide industrial applications, yet its large-scale production still relies on the energy-intensive anthraquinone process. Photocatalytic synthesis of H₂O₂ under visible light offers a sustainable alternative but remains limited by inefficient charge separation and mass transport in extended framework materials. Herein, we report the modular construction of two porphyrin-based double-cavity metallacages via orthogonal Pt(II)/carboxylate/pyridine and Zn-porphyrin/pyridine coordination. The resulting metallacages feature an intrinsic donor-acceptor architecture that promotes photoinduced electron transfer and charge separation. Encapsulation of electron-rich aromatic guests (triphenylene or benzotrithiophene) further stabilizes the charge-separated state and prolongs carrier lifetimes, thereby enhancing the photocatalytic H₂O₂ generation with a rate of 4037 µmol·g⁻¹·h⁻¹ in the presence of benzyl alcohol, among the highest reported values for visible-light supramolecular photocatalysts. This work establishes discrete metallacages and their host–guest complexes as an emerging platform for supramolecular photocatalysis and rational H₂O₂ photosynthesis, which will pave the way for the future development of metallacages in photocatalytic applications.