Molecularly Programmed MOF Electrodes Enable Spatial Regulation of Triple-Phase Boundaries in Li-O₂ Batteries.

Abstract

Li-O₂ batteries are limited by spatially heterogeneous triple-phase boundary (TPB) reactions caused by opposing Li⁺ and O₂ transport, leading to localized Li₂O₂ nucleation, pore blockage, and restricted capacity. Here, we demonstrate nanoscale transport programming of a hierarchical metal-organic framework (MIL-121) to decouple and regulate ionic and gaseous flux. Thermal activation generates anhydride sites for orthogonal functionalization with Li⁺-coordinating groups (PMIL-121@Li) and O₂-binding Fe-porphyrin motifs (PMIL-121@Heme). These functionalities independently enhance Li⁺ conduction and local O₂ availability, rebalancing reactant supply at the TPB. When assembled into a spatially encoded multilayer architecture, the functionalized MOF layers directionally modulate reactant transport across electrode depth, converting localized TPBs into a uniformly extended reaction interface. This enables homogeneous Li₂O₂ deposition, delivering 4.3 mAh cm^-2 at 0.1 mA cm^-2 with stable cycling over 45 cycles. This work establishes molecularly engineered MOFs as a platform for regulating multiphase transport and stabilizing TPB dynamics in Li-O₂ systems.