Halogen-bridge-regulated π-π stacking enables efficient photocatalytic nitrogen reduction in metal-organic frameworks

Metal-organic frameworks (MOFs) incorporating donor-acceptor (D-A) architectures have emerged as promising platforms for photocatalysts, yet their efficiency is often limited by inefficient electron transport, particularly along the out-of-plane direction. Herein, we report a series of D-A-D type MOFs, in which iron-nodes act as electron donors and naphthalene diimide (NDI) units serve as acceptors. Notably, adjacent NDI cores exhibit pronounced π-π stacking interactions, which can be precisely modulated by halogen bridges (F, Cl, and Br), thereby regulating out-of-plane charge transport. Among these materials, FeF-pyNDI delivers the highest photocatalytic nitrogen reduction reaction (pNRR) performance, achieving an NH₃ yield rate of 341 μmol g^-1 h^-1, representing one of the highest reported values of MOF-based photocatalysts. Combined structural characterization and theoretical simulations reveal that the F-pillared analogue can significantly strengthen π-π interactions owing to its smaller radius, thereby promoting interlayer electron transport and prolonging carrier lifetimes. This work provides a viable strategy for regulating π-π interactions and charge transport in MOFs, opening new avenues for the design of advanced MOF photocatalysts.