Spin-dependent activity of cobalt contained hydroxy double perovskite for efficient antibiotic removal via peroxymonosulfate activation

•Mixed-spin state of Co in CoxZn1-xSn(OH)6 (CoxZn1-xSH) is achieved by increase of x.•The mixed-spin state of Co2+ balance reaction kinetics and adsorption of reactants.•Co0.5Zn0.5SH shows excellent activity, adaptability, and biosecurity in TCH removal.•Co0.5Zn0.5SH exhibits highly covalent Co-OH bonds, optimizing PMS adsorption.•SO4•−, •OH, O2•−, and 1O2 serve as active species of catalytic oxidation reaction. Cobalt-containing catalysts exhibit good performance in the advancement of efficient catalytic oxidation reactions. However, achieving an optimal balance between reaction kinetics and reactant adsorption that is governed by the spin states of Co ions remains a significant challenge. This study aims to develop a convenient compositional tuning strategy to achieve such balance in stable CoxZn1-xSn(OH)6 perovskite hydroxides. The effect of varying spin state on peroxymonosulfate activation and tetracycline hydrochloride removal is systematically investigated. The magnetic properties analysis reveals that the content of high-spin Co2+ ions in octahedral site increases with Co content (x) and reaches 59.5 % in Co0.5Zn0.5Sn(OH)6. Experimental results and DFT calculations reveal that the spin state transition of Co2+ ions enhances the interaction between Co and O atoms. This enhanced interaction not only improves the reactivity due to the formation of highly covalent Co-OH bonds that serve as catalytically activated charge transfer channels, but also optimizes the suitable adsorption energy of PMS molecules at −3.52 eV for Co0.5Zn0.5Sn(OH)6. Consequently, Co0.5Zn0.5Sn(OH)6 shows superior catalytic activity, achieving nearly 100 % antibiotic removal efficiency within just 10 min, surpassing previously reported catalysts. These findings underscore the potential of compositional tuning spin states of transition metal ions in advancing oxidation processes and designing innovative catalysts.