Computational and experimental insights into single-atom catalysts supported on g-C3N4: Unraveling the superior stability and catalytic activity of Rh in hydroformylation reactions

Single-atom catalysts (SACs) have emerged as a promising class of materials, leveraging the benefits of both homogeneous and heterogeneous catalysis to enhance efficiency and selectivity. In this work we have investigated the catalytic performance of SACs supported on graphitic carbon nitride (g-C₃N₄) for hydroformylation reactions. A systematic evaluation of nine transition metal SACs (Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, and Pt) anchored on g-C₃N₄ was conducted using a combination of Density Functional Theory (DFT) calculations and experimental validation. Computational results indicate that at higher metal loadings, most metal atoms tend to migrate into the interlayers of g-C₃N₄, reducing their accessibility to reactant species and limiting their involvement in the catalytic process. However, Ru, Os, Ir, and Co single atoms remain stabilized on the heptazine rings, residing on the outermost layer and preserving active sites, albeit with lower predicted catalytic activity compared to Rh, while Fe, Ni, Pd, and Pt preferentially localize within the interlayers. Ru, Rh, and Co SACs anchored on g-C₃N₄ were experimentally synthesized and characterized using Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), and in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), along with catalytic testing, confirming the single-atom nature of the catalysts and corroborating the theoretical findings.