Encapsulation of metal nanoparticles by support-derived materials known as the classical strong metal–support interaction (SMSI) often happens upon thermal treatment of supported metal catalysts at high temperatures (≥500 °C) and consequently lowers the catalytic performance due to blockage of metal active sites. Here, we show that this SMSI state can be constructed in a Ru–MoO3 catalyst using CO2 hydrogenation reaction gas and at a low temperature of 250 °C, which favors the selective CO2 hydrogenation to CO. During the reaction, Ru nanoparticles facilitate reduction of MoO3 to generate active MoO3–x overlayers with oxygen vacancies, which migrate onto Ru nanoparticles’ surface and form the encapsulated structure, that is, Ru@MoO3–x . The formed SMSI state changes 100% CH4 selectivity on fresh Ru particle surfaces to above 99.0% CO selectivity with excellent activity and long-term catalytic stability. The encapsulating oxide layers can be removed via O2 treatment, switching back completely to the methanation. This work suggests that the encapsulation of metal nanocatalysts can be dynamically generated in real reactions, which helps to gain the target products with high activity.

Encapsulation of metal nanocatalysts by supportderived materials is well known as a classical strong metal−support interaction (SMSI) effect that occurs almost exclusively with active oxide supports and often blocks metal-catalyzed surface reactions. In the present work this classical SMSI process has been surprisingly observed between metal nanoparticles, e.g., Ni, Fe, Co, and Ru, and inert hexagonal boron nitride (h-BN) nanosheets. We find that weak oxidizing gases such as CO 2 and H 2 O induce the encapsulation of nickel (Ni) nanoparticles by ultrathin boron oxide (BO x ) overlayers derived from the h-BN support (Ni@BO x / h-BN) during the dry reforming of methane (DRM) reaction. Insitu surface characterization and theory calculations reveal that surface B−O and B−OH sites in the formed BO x encapsulation overlayers work synergistically with surface Ni sites to promote the DRM process rather than blocking the surface reactions.

The strong metal−support interaction (SMSI) is one of the most important concepts in heterogeneous catalysis, which has been widely investigated between metals and active oxides triggered by reductive atmospheres. Here, we report the oxidative strong metal− support interaction (O-SMSI) effect between Pt nanoparticles (NPs) and inert hexagonal boron nitride (h-BN) sheets, in which Pt NPs are encapsulated by oxidized boron (BO x ) overlayers derived from the h-BN support under oxidative conditions. De-encapsulation of Pt NPs has been achieved by washing in water, and the residual ultrathin BO x overlayers work synergistically with surface Pt sites for enhancing CO oxidation reaction. The O-SMSI effect is also present in other h-BN-supported metal catalysts such as Au, Rh, Ru, and Ir within different oxidative atmospheres including O 2 and CO 2 , which is determined by metal−boron interaction and O affinity of metals.

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