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

ABSTRACT 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/H 2 directly hydrogenates lattice carbonate in calcite to CH 4 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 CO 2 management. Operando techniques show a permeable amorphous interphase that dynamically encapsulates Pt, transports CO 3 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 CH 4 . It is resolved that a low‑temperature interfacial CO 2 release is diagnostic of boundary decomposition. Kinetics separate a CO 3 2− ‑diffusion‑limited solid‑state path at low temperatures from a high‑temperature route akin to gaseous‑CO 2 hydrogenation. The hydrogenated solid is re‐carbonated by CO 2 , regenerating CaCO 3 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.