Regioselective Arene C–H Borylation with a MOF-Immobilized Iridium Bipyridine Catalyst

Postsynthetic ligand exchange and metalation have been used to immobilize iridium bipyridine precatalysts in MFU-4l with controlled loadings. The resulting materials, 1-Ir-x (x = 0.1–0.5), exhibit high activity for catalytic C–H borylation of arenes, and 1-Ir-0.5 achieves up to 1560 turnover numbers per Ir for toluene substrate. Remarkably, 1-Ir-0.5 exhibits high meta:para product regioselectivity compared to a homogeneous catalyst analogue for arene substrates bearing bulky triisopropylsilyl groups. Density functional theory (DFT) calculations reveal that steric constraints imposed by metal-organic framework (MOF) pore confinement increase the free energy barrier for para C–H activation, biasing product formation toward the meta isomer.本研究通过后合成配体交换与金属化方法，将联吡啶铱预催化剂固定于MFU-4l金属有机框架中，并实现了可控的催化剂负载量。所得材料1-Ir-x（x=0.1~0.5）对芳烃的催化C-H硼化反应表现出优异的催化活性，其中1-Ir-0.5在以甲苯为反应底物时，每摩尔铱的转化数可达1560。值得注意的是，相较于对应均相催化剂，当芳烃底物带有大位阻三异丙基硅基基团时，1-Ir-0.5展现出更高的间位:对位产物区域选择性。密度泛函理论（DFT）计算结果表明，金属有机框架（MOF）孔道限域所引入的位阻约束，提升了对位C-H活化步骤的自由能垒，从而使产物生成偏向间位异构体。