Fig. 2: DFT calculations and proposed reaction mechanism for CaL@DRM.

a Calculated energy profiles of CO₂ adsorption and dissociation on the Ni₄–CaO(100) surface; the black dashed line represents the *H-assistant CO₂ dissociation of *HCOO, the orange dashed line represent the direct CO₂ dissociation to *CO, and the blue dashed line represents the *H-assistant *COOH pathway. b Calculated energy profiles of CH₄ dehydrogenation with the assistance of *OH species on the Ni₄–CaO(100) surface (red dashed line); the green dashed line represents the *CH₂ dissociates to *CH, and the brown dashed line represents the *CH₂OH dissociates to *CHOH. c Schematic illustration of reaction network for the CaL@DRM on the Ni₄–CaO(100) surface. The corresponding activation energy E_a (red) and reaction energy (black) in the unit of eV for each step are also included. The optimized structures of reaction intermediates and transition state (TS) are shown in b and c. Red: O; green: Ca; blue: Ni; yellow: O of CO₂; Pink: H of CH₄. This notation is used throughout the paper.