Engineering Cavity and Aperture Binding Sites Within a Metal–Organic Cage for Up‐ and Down‐Regulation of Catalysis
Yan Xu, Gen Li, Shihang Liang, Gaël De Leener, Michel Luhmer, Roy Lavendomme, En‐Qing Gao, Dawei Zhang
Abstract
Abstract Engineering molecular recognition events into catalytic systems to precisely control the up‐ or down‐regulation of catalysis in a biomimetic fashion is a challenging goal in supramolecular chemistry. In this work, we report on the construction of a new metal–organic cage, Zn II 4 L 4 tetrahedron 1 , using a protonated azacalix[3](2,6)pyridine‐based ligand as the capping faces. The cage features a large cavity and wide gaps between its faces, enabling the simultaneous binding of anionic guests centrally and peripherally. Encapsulation of α‐Mo 8 O 26 4− within the T ‐symmetric tetrahedron 1 leads to a C 3 ‐symmetric inclusion complex Mo 8 O 26 4− ⊂ 1 . The apertures of Mo 8 O 26 4− ⊂ 1 act as secondary binding sites for accommodating tetraarylborate guests or for providing access to the included Mo 8 O 26 4− for catalyzing reactions. Catalytic experiments demonstrated that inclusion within 1 significantly enhances the catalytic activity of Mo 8 O 26 4− for the oxidation of sulfides into sulfoxides. In contrast, peripheral binding of the bulky tetraarylborate anion to the inclusion complex Mo 8 O 26 4− ⊂ 1 effectively inhibits its catalytic activity by obstructing access to the catalytic active sites of Mo 8 O 26 4− .