Abstract
<jats:p>Metal-organic frameworks often transform electrochemically into highly active oxyhydroxide electrocatalysts, raising the fundamental question of what chemical information from chemically distinct precursors survives this transformation and how it shapes activity. Here, through operando investigation of Ni and NiFe frameworks built from two linkers, terephthalic acid and 2-methylimidazole, we establish that linker identity controls the transformation pathway, although the transformed active species remain chemically similar. We show that the relative performance of the two linkers reverses with pH. In dilute KOH the terephthalic acid framework outperforms, while in concentrated KOH the 2-methylimidazole framework shows better activity. Turnover frequency analysis resolves this apparent contradiction: the 2-methylimidazole framework has intrinsically superior active sites but exposes fewer of them. At higher KOH concentration, the accessibility penalty is reduced and 2-methylimidazole shows superior absolute activity. Operando Raman spectroscopy further shows that the terephthalic acid framework activates earlier. These trends correlate with the distinct wettability of the precatalysts, indicating that the linker imprints a microenvironment that regulates reconstruction, site exposure and intrinsic activity. Our results demonstrate that the linker acts as a chemical memory element affecting both the accessibility and the quality of the active sites despite substantial loss of the original framework during electrochemical transformation.</jats:p>