Size-Dependent Lattice Compression Drives Electronic Modulation of Pt Single-Atom Sites in Thermally Constructed MOFs

Precise regulation of the electronic structure of single-atom catalysts (SACs) remains challenging because conventional approaches rely on chemical perturbations that often disrupt structural uniformity and provide limited tunability. Here, we report a physical strategy for continuous, size-dependent electronic modulation of Pt single atoms using lateral dimension as an experimentally accessible structural descriptor. Pt single atoms were pre-coordinated in Pt-TCPP units and assembled with Co²⁺ into two-dimensional Co@Pt-SAC nanosheets. Temperature-programmed cooling enabled precise control of nanosheet lateral size while preserving the primary Pt─N coordination environment. Decreasing nanosheet size induced progressive lattice compression, evidenced by the shift of the apparent Pt─N scattering feature in FT-EXAFS spectra from 1.64 to 1.57 Å. Meanwhile, the local electrostatic potential at Pt sites increased from -16.880 to -14.872 kcal mol^-1, indicating pronounced Pt-centered electronic modulation. This modulation strengthened the interaction between Pt sites and triiodide species, accelerating interfacial charge transfer during the I₃ ^-/I^- redox process. These findings establish a direct correlation between lateral size-dependent lattice evolution and the electronic structure of single-atom active sites, offering a general physical route for continuous electronic tuning of SACs without altering their primary coordination chemistry.