EXAFS-Resolved Node Asymmetry Links Local Distortions to Lattice Structure in High-Entropy MOFs

High-entropy materials derive their functionality from chemical complexity, yet this same complexity obscures quantitative understanding of local structure, even when long-range crystallographic order is entropically stabilized. In high-entropy frameworks, local coordination environments are intrinsically heterogeneous, and existing structural descriptions rely largely on ensemble-averaged probes that mask element-specific distortions. Although extended X-ray absorption fine structure (EXAFS) spectroscopy provides direct sensitivity to local coordination geometry, its application to chemically complex materials is constrained by overlapping scattering pathways, strong parameter correlations, and limited atomic number contrast. Here, we establish a compositionally resolved and internally calibrated XRD–EXAFS–DFT framework using a model high-entropy metal–organic framework (HE-MOF) platform. A porphyrinic linker is used to construct a three-dimensional hexagonal MOF featuring trinuclear bipyramidal M₃O secondary building units, enabling precise stoichiometric control across mono-, bi-, tri-, and five-metal frameworks incorporating Fe, Co, Ni, Cu, and Zn. Nearly twenty compositions—corresponding to ~50 metal K-edge EXAFS measurements—are systematically interrogated to generate an element-specific description of local coordination environments. This controlled dataset establishes absolute bond-distance baselines, enables quantitative deconvolution of metal–oxygen and metal–metal scattering contributions, and reveals heterometal-induced node-level asymmetry inaccessible by diffraction alone. Density functional theory–optimized SBU geometries provide physically grounded constraints for EXAFS fitting and independently validate the experimentally resolved distortions. High-resolution synchrotron XRD reveals reproducible, composition-dependent lattice-parameter shifts despite conservation of framework topology, demonstrating that local coordination asymmetry propagates coherently to the lattice scale. Stoichiometrically constrained bimetallic nodes define the structural extremes of distortion and bound the heterogeneous local environments observed in tri-metallic and five-metal HE-MOFs. Time-resolved XRD and ICP-MS further reveal that node composition evolves dynamically during synthesis through sequential metal uptake and exchange, a behavior rationalized by molecular dynamics simulations of metal–nitrate precursor coordination. Collectively, this work establishes a quantitative link between node-level asymmetry and lattice-scale response in high-entropy MOFs.