Metal–Organic Framework‐Confined Iron Pincer Complex for Highly Efficient and Selective Borylation of Methane and Ethane

ABSTRACT

We report the design and development of a heterogeneous NNP‐pincer ligand, 6‐((diisopropylphosphaneyl)amino)‐(2,2′‐bipyridine), which is integrated within a porous zirconium metal–organic framework (mNNP‐UiO‐67) to synthesize highly active earth‐abundant metal catalysts for alkane functionalization. The mNNP‐UiO‐67 MOF‐supported mononuclear iron(II)‐dihydride (mNNP‐UiO‐FeH ₂ ) exhibits high efficiency in catalyzing selective monoborylation of methane and ethane. mNNP‐UiO‐FeH ₂ ‐catalyzed borylation of methane using pinacolborane (HBpin) produces CH ₃ Bpin in 76% yield, while significantly suppressing the formation of thermodynamically favored over‐borylated products. The catalyst remains active over six recycling cycles, achieving a cumulative turnover number (TON) of 10,793, a methane utilization efficiency of 5.5%, and a space‐time productivity of 13.5 gL ⁻¹ h ⁻¹ . The catalyst is also effective for ethane activation, yielding 36% of C ₂ H ₅ Bpin with 100% selectivity and a TON of 774. In stark contrast, the analogous homogeneous control is barely active, giving a TON of only 8 in methane borylation due to its rapid decomposition. Experimental results indicate that the stabilization of NNP‐Fe ^II H ₂ active sites and the catalytic intermediates such as NNP‐Fe ⁰ and NNP‐Fe ^II H(Bpin) within the MOF through active‐site isolation is crucial for the remarkably high activity and selectivity. Mechanistic studies suggest the σ ‐bond metathesis between the Fe─Bpin bond of NNP‐Fe ^II H(Bpin) and the C─H bond of methane as turnover‐limiting in the catalytic cycle.