Quantifying Microenvironment Effect on Metal Electronic Structure With Experimentally Accessible Descriptor: Examples...

The chemical microenvironment surrounding metal nanoparticles (NPs) plays crucial roles in regulating their electronic structures. However, due to the lack of quantitative descriptor, such effect has been understood largely in a qualitative manner. To address this issue, a series of reticular metal-organic frameworks (MOFs) with diverse functional groups (MIP-206-X, X = OH, OCH₃, H, Cl, and F) were synthesized, and Pt NPs with similar sizes and loadings were incorporated to afford Pt@MIP-206-X for ammonia borane methanolysis. X-ray absorption near edge structure (XANES) was adopted to determine the d-orbital occupancy of Pt, and the electronic contribution from MOFs was quantified as the descriptor Δe, which was demonstrated to accurately describe the Pt-methanol adsorption strength (quantified by activation entropy and methanol desorption temperature) and exhibit an excellent linear correlation with catalytic activity. Isotopic analyses and DFT calculations revealed that a larger Δe strengthens methanol adsorption on Pt, promotes O─H bond cleavage as the rate-determining step (RDS), and leads to enhanced activity.