Beyond Planar Architectures: Oxacalix[4]Arene ‐Bridged 3D Covalent Organic Frameworks with Saddle‐Shaped π‐Cavities for Efficient Hydrogen Peroxide Photogeneration and Non‐Covalent C 60 Confinement

In this work, two calixarene-based macrocyclic 3D COFs (XJU-3, XJU-4) are successfully developed by overcoming conformational instability via intramolecular heteroatom anchoring and peripheral structural extension. The stabilized saddle-shaped conformation endows XJU-4 with exceptional crystallinity and directional charge transfer channels, achieving an efficient hydrogen peroxide (H₂O₂) production rate of 8384 µmol g ¹ h^-1 under pure water and oxygen (O₂) conditions, which further rises to 24605 µmol g ¹ h^-1 with a sacrificial agent. Combined experimental and theoretical analyses reveal that the curved π-cavity facilitates O₂ activation through enhanced electron-withdrawing effects, while the orthogonal dimer configuration promotes singlet oxygen (¹O₂) intermediates via reduced singlet-triplet energy gaps (ΔE_S-T). Building on this framework, the potential of calixarene cavities is further demonstrated as supramolecular hosts-C₆₀ is selectively encapsulated within their π-rich pockets through non-covalent interactions, distinct from conventional pore confinement or covalent linkage strategies. This host-guest synergy enhances charge transfer pathways, as evidenced by luminescence quenching and orbital localization, showcasing the versatility of these COFs in both catalysis and functional composite design. The work establishes a paradigm for engineering conformation-stable macrocycles into 3D COFs, expanding their functional design for solar energy conversion systems.