Piezo-driven cation-exchange induced regulation of single Pt sites on poly(heptazine imide) triggers photocatalytic NO oxidation

The development of heterogeneous metal-photocatalysts is of significant importance for oxygen reduction in nitric oxide photooxidation processes. However, designing and controlling metal/photocatalytic bifunctional solid catalysts with well-defined structure (site isolation) remains a key challenge. Here, we demonstrate the integration of unique single platinum sites into potassium poly(heptazine imide) (K-PHI) in a liquid-phase system under mechanical force via ultrasonic treatment. Our strategy relies on a negative PHI layer with potassium ions (K⁺) as charge compensation, which enables K⁺ exchange and reduction through the piezoelectric effect with atomically dispersed platinum in the matrix with excellent accessibility. Pt-supported PHI was prepared and comprehensively characterized using various techniques, including X-ray photoelectron spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, and X-ray absorption spectroscopy. The Pt-PHI photocatalyst exhibits exceptional chemical stability and activity in the one-electron O₂ reduction reaction involved in the oxidation of NO. The electron donation and electron back-donation of Pt can induce the interaction between the π* antibonding orbitals of the end-on O₂ adsorption configuration and the d-orbitals of the Pt single atom. The proximity and synergistic effects significantly enhance the photo/platinum dual catalytic activity, offering a new avenue for designing site-isolated catalysts for efficient O2 activation involved in environmental remediation.