Reticular Construction of Porphyrin-Pyrazolate Frameworks for Markovnikov-Selective Wacker-Type Oxidation of Styrenes
You-Tuo Zhang1,2, Tao He1,2, Xiang-Jing Kong2
1State Key Laboratory of Materials Low-Carbon Recycling, Beijing University of Technology, Beijing100124, China.
Abstract:
Reticular chemistry enables construction of metal-organic frameworks (MOFs) with predictable topologies by matching the connectivity and geometry of nodes and linkers. However, extending such design principles to pyrazolate systems remains challenging due to the fixed connectivity and geometric directionality of their metal nodes, which limits structural diversity. Herein, we report a building-unit connectivity transposition approach that bridges these two coordination regimes by transposing the connectivity roles of linkers and metal nodes. An octatopic porphyrin-based pyrazolate ligand, 5,10,15,20-tetrakis(3,5-di(1H-pyrazol-4-yl)phenyl)porphyrin (H8TDPP), was designed to mimic the geometry of a typical D4h-symmetric Zr6 node in carboxylate frameworks, which can match the Oh-type Co4OPz6 cluster, affording three-dimensional frameworks BUT-59(M) (M = Co, Mn or Fe, where M denotes the metal incorporated into the porphyrin center). Single-crystal X-ray diffraction reveals a cubic structure composed of geometrically encoded 8-connected linkers and 6-connected metal clusters, representing the first ocu-a network among azolate MOFs. BUT-59 exhibits permanent porosity and chemical stability, maintaining its crystallinity and pore structure under strongly basic conditions. Featuring abundant accessible porphyrin-Co sites within its pores, BUT-59(Co) acts as an efficient heterogeneous catalyst for the Markovnikov-selective Wacker-type oxidation of styrenes under mild conditions. Its catalytic performance is comparable to that of homogeneous cobalt catalysts, while maintaining high recyclability without structural degradation. These results highlight the strength of connectivity role transposition in unlocking specific topological access in systems with geometrically constrained building units, thereby expanding the structural diversity and functionality of robust MOFs.
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