Activating a Metallization Switch for Record Hydrogen Evolution in Single‐Atom Modified Polar MOF Piezocatalysts

ABSTRACT Piezocatalytic hydrogen evolution enables the conversion of mechanical energy into chemical fuels, but its efficiency is constrained by a trade‐off between piezoelectric polarization and electronic conductivity. Strong piezoelectric polarization is essential for sufficient driving force, yet highly polar materials typically suffer from poor conductivity, which limits bulk‐to‐surface charge transport. Conversely, enhancing conductivity often compromises piezoelectric performance, resulting in a bottleneck in piezocatalysis. Herein, we decouple piezoelectricity and conductivity using atomically dispersed nickel single atoms on amino‐functionalized UiO‐66 (Ni SAs@UiO‐66‐NH 2 ). Introducing polar amino groups and asymmetric Ni─N coordination significantly enhances the piezoelectric response, increasing the piezoelectric coefficient d 33 from 48 to 242 pm V −1 . Simultaneously, hydrogen adsorption at Ni sites under mechanical stress triggers a pressure‐induced semiconductor‐to‐metal transition, creating transient metallic conduction pathways that facilitate efficient electron extraction without sacrificing bulk polarization. As a result, hydrogen adsorption sites shift from framework carbons to Ni centers, yielding near‐optimal H * adsorption energetics (ΔG H * approximately 0.12 eV at 100 MPa), and enabling rapid polarization‐driven hydrogen evolution. Consequently, the Ni SAs@UiO‐66‐NH 2 catalyst achieves exceptional hydrogen evolution rate of 1871 µmol g −1 h −1 in deionized water and 17 613 µmol g −1 h −1 in methanol‐containing media, surpassing reported MOF‐based piezocatalysts and competing with leading photo‐piezocatalytic and photocatalytic systems.