Remove the innermost atom of a magnetic multi-shell gold nanoparticle for near-unity conversion of CO to CO.

Few reports on paramagnetic metal nanoparticles with atomic precision and their difficult tailoring retard the insightful investigation of metal nanoparticle paramagnetism. Herein, we introduced a thiol-iodine mixture ligand-protecting strategy to successfully synthesize multi-shell paramagnetic [AuI(TBBT) (I: iodine, TBBT: 4-tert-butylphenylthiolate)]. The innermost Au atom was successfully removed via thiol induction without altering the structure framework to produce diamagnetic AuI(TBBT) with local ligand arrangement changed (butterfly effect), which could be further transformed into paramagnetic [AuI(TBBT)] via hydrogen peroxide oxidation. The spin populations of both paramagnetic nanoparticles are more densely distributed on surface iodine than sulfur. Diamagnetic AuI(TBBT) exhibited a Faradaic efficiency of ~100% at -0.57 volt during the electrocatalytic reduction of carbon dioxide to carbon monoxide, while paramagnetic AuI(TBBT) and [AuI(TBBT)] exhibited the maximum Faradaic efficiency of 87% at -0.67 volt and 90% at -0.57 volt, respectively, indicating the spin-catalytic activity correlation.