Reactant‑Transporting Metal-Support Interaction for Lattice Carbonate‑to‑Methane Catalysis

As a core concept of heterogeneous catalysis, metal-support interactions are pivotal controlling activity, selectivity, and stability via electronic and geometric effects. Here, we report a reactant‑transporting form of metal support interaction (MSI), named as strong metal-reactive support interaction (SMRSI) where Pt/H₂ directly hydrogenates lattice carbonate in calcite to CH₄ with ≤ 415 °C onset and ∼98% selectivity (390-510°C). Because lattice carbon in carbonate minerals constitutes Earth's largest carbon reservoir, enabling low‑temperature lattice-carbonate conversion offers a catalytic lever to accelerate the slow carbon cycle (ACC) complementary to fast carbon cycle (FCC)‑based CO₂ management. Operando techniques show a permeable amorphous interphase that dynamically encapsulates Pt, transports CO₃ ^2- to active sites, and crystallizes into Ca(OH)₂, thereby sustaining a mobile triple‑phase boundary, where carbonate‑derived *CO intermediate was hydrogenated to CH₄. It is resolved that a low‑temperature interfacial CO₂ release is diagnostic of boundary decomposition. Kinetics separate a CO₃ ^2-‑diffusion‑limited solid‑state path at low temperatures from a high‑temperature route akin to gaseous‑CO₂ hydrogenation. The hydrogenated solid is re-carbonated by CO₂, regenerating CaCO₃ and retaining selectivity over cycles. Conceptually, the SMRSI extends MSI from electronic/geometric tuning to reactant transport, illustrating how moving solid-solid@gas interfaces mediate transformations of solid reactants.