Site-selective valence isomerism as a unified electronic trigger for magnetism, chirality, and catalysis in Ni-carboxylate MOFs.
basic_science · Level V
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- Record sourced from PubMed, PMID 41957367.
- Also identified by DOI 10.1038/s41467-026-71747-8.
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Abstract
Valence modulation at metal nodes provides a fundamental route to couple electronic structure with functional properties in metal-organic frameworks (MOFs). Achieving precise and stimulus-independent control of metal oxidation states within an isostructural lattice remains a central challenge. Here we demonstrate valence isomerism in a Ni-carboxylate framework, Ni<sub>3</sub>(OH)<sub>2</sub>(Cam)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>, by combining pH adjustment with vortex-driven stirring. This approach yields an isostructural pair consisting of a Ni(II) parent phase and a mixed-valence Ni(II)/Ni(III) analog, in which approximately 25% of the Ni centers are oxidized to low-spin Ni<sup>3+</sup> selectively at the Ni(1) sites. Subtle valence reconfiguration reorganizes the intrachain interactions within the [Ni<sub>3</sub>(OH)<sub>2</sub>] chains, reinforcing ferrimagnetic order and enhancing net magnetization. Concomitantly, the short-wavelength circular dichroism signals invert, and the oxygen-evolution overpotential decreases by ~100 mV. These results establish valence isomerism as an electronic trigger that coherently couples magnetic, chiroptical and catalytic properties in MOFs, offering a general design principle for multifunctionality in reticular materials.