Rational Control of the Selectivity of a Ruthenium Catalyst for Hydrogenation of 4‐Nitrostyrene by Strain Regulation

Tuning the selectivity of metal catalysts is of paramount importance yet a great challenge. A new strategy to effectively control the selectivity of metal catalysts, by tuning the lattice strain, is reported. A certain amount of Co atoms is introduced into Ru catalysts to compress the Ru lattice, as confirmed by aberration‐corrected high‐resolution transmission electron microscopy (HRTEM) and X‐ray absorption fine structure (XAFS) measurements. We discover that the lattice strain of Ru catalysts can greatly affect their selectivity, and Ru with 3 % lattice compression exhibits extremely high catalytic selectivity for hydrogenation of 4‐nitrostyrene to 4‐aminostyrene compared to pristine Ru (99 % vs. 66 %). Theoretical studies confirm that the optimized lateral compressive strain facilitates hydrogenation of the nitro group but impedes the hydrogenation of the vinyl group. This study provides a new guideline for designing metal catalysts with high selectivity.     

Direct Imaging of Atomically Dispersed Molybdenum that Enables Location of Aluminum in the Framework of Zeolite ZSM-5

Integrated differential phase-contrast scanning transmission electron microscopy (iDPC-STEM) is capable of directly probing guest molecules in zeolites, owing to its sufficient and interpretable image contrast for both heavy and light elements under low-dose conditions. This unique ability is demonstrated by imaging volatile organic compounds adsorbed in zeolite Silicalite-1; iDPC-STEM was then used to investigate molybdenum supported on various zeolites including Silicalite-1, ZSM-5, and mordenite. Isolated single-Mo clusters were observed in the micropores of ZSM-5, demonstrating the crucial role of framework Al in driving Mo atomically dispersed into the micropores. Importantly, the specific one-to-one Mo-Al interaction makes it possible to locate Al atoms, that is, catalytic active sites, in the ZSM-5 framework from the images, according to the positions of Mo atoms in the micropores.     

Tuning the Selectivity of Catalytic Carbon Dioxide Hydrogenation over Iridium/Cerium Oxide Catalysts with a Strong Metal–Support Interaction

A one‐step ligand‐free method based on an adsorption–precipitation process was developed to fabricate iridium/cerium oxide (Ir/CeO₂) nanocatalysts. Ir species demonstrated a strong metal–support interaction (SMSI) with the CeO₂ substrate. The chemical state of Ir could be finely tuned by altering the loading of the metal. In the carbon dioxide (CO₂) hydrogenation reaction it was shown that the chemical state of Ir species—induced by a SMSI—has a major impact on the reaction selectivity. Direct evidence is provided indicating that a single‐site catalyst is not a prerequisite for inhibition of methanation and sole production of carbon monoxide (CO) in CO₂ hydrogenation. Instead, modulation of the chemical state of metal species by a strong metal–support interaction is more important for regulation of the observed selectivity (metallic Ir particles select for methane while partially oxidized Ir species select for CO production). The study provides insight into heterogeneous catalysts at nano, sub‐nano, and atomic scales.     

Concerted Bimetallic Nanocluster Synthesis and Encapsulation via Induced Zeolite Framework Demetallation for Shape and Substrate Selective Heterogeneous Catalysis

Bimetallic nanoparticle encapsulation in microporous zeolite crystals is a promising route for producing catalysts with unprecedented reaction selectivities. Herein, a novel synthetic approach was developed to produce PtZn_x nanoclusters encapsulated inside zeolite micropores by introducing Pt²⁺ cations into a zincosilicate framework via ion exchange, and subsequent controlled demetallation and alloying with framework Zn. The resulting zeolites featured nanoclusters with sizes of approximately 1 nm, having an interatomic structure corresponding to a PtZn_x alloy as confirmed by pair distribution function (PDF) analysis. These materials featured simultaneous shape and substrate specificity demonstrated by the selective production of p‐chloroaniline from the competitive hydrogenation of p‐chloronitrobenzene and 1,3‐dimethyl‐5‐nitrobenzene.