Covalent-bond-linked monolayer fullerene network as a spin sponge for spin-triplet O2 activation and CO oxidation

Recently, a novel class of 2D carbon material, covalent-bond-linked monolayer ${\mathrm{C}}_{60}$ networks with quasihexagonal phase (qHP-${\mathrm{C}}_{60}$) was experimentally fabricated [Hou et al., Nature (London) 606, 507 (2022)]. Here, using first-principles calculations, we predict that such a two-dimensional network serves as an ideal platform in stabilizing transition metals (TM: Mn, Fe, Co, and Ni) into dispersive single atoms, exhibiting remarkable efficiency for spin-triplet ${\mathrm{O}}_{2}$ activation and CO oxidation with low reaction barriers $(0.3\ensuremath{\sim}0.5\phantom{\rule{0.16em}{0ex}}\mathrm{eV})$. First, the two-dimensional qHP-${\mathrm{C}}_{60}$ network acts as an electronic reservoir responsible for charge transfer to the antibonding orbital of ${\mathrm{O}}_{2}$. Second, and important, it functions as a spin sponge in accommodation of the reduced spin magnetic moment from ${\mathrm{O}}_{2}$ molecule, facilitating its spin triplet-to-singlet transition in the framework of Wigner's spin conservation rule. Delicate quantitative calculations demonstrate that the spin component contributes approximately twice as significantly as that of pure charge transfer in reducing the activation barrier for CO oxidation.