Pore-Engineered Porphyrinic Metal–Organic Frameworks Via Isoreticular Expansion for Accelerated N–H Insertion

N–H insertion offers an atom-economical route to α-amino esters and valuable unnatural amino acid derivatives, but their efficiency is often hampered by catalyst deactivation and diffusion limitations. Herein, we report an isoreticularly expanded porphyrinic metal–organic framework, PCN-323, constructed from an elongated linker and the same shp-a topology with PCN-223, forming 12-connected Zr6 clusters and 1D triangular channels with an expanded pore diameter of 18 Å. Postsynthetic metalation affords PCN-323(Fe), which efficiently catalyzes N–H insertion of amines with ethyl diazoacetate under ambient conditions. Compared to PCN-223(Fe), the expanded framework delivers markedly improved double-insertion yields for sterically demanding substrates, confirming pore expansion mitigates diffusion constraints without altering intrinsic reactivity. Calculations suggest a carbene-mediated pathway, with mass transport emerging as the dominant performance-limiting factor. This work establishes isoreticular expansion as an effective strategy for enhancing diffusion-controlled catalysis, and it provides a fundamental principle for tuning mass transport in porous catalysts.