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1. Ultrasmall Cu Nanoparticles Supported on Crystalline, Mesoporous ZnO for Selective CO ₂ Hydrogenation

   https://doi.org/10.1002/cctc.202301077  

   Hu, Mingzhen; Lu, Xingxu; Zhu, Chunxiang; Yang, Tiangang; Tan, Haiyan; Jin, Lei; Kerns, Peter; Meng, Michael; Suib, Steven L; Gao, Puxian; et al (February 2024, ChemCatChem)

   Abstract Converting CO₂to value‐added chemicals,e. g., CH₃OH, is highly desirable in terms of the carbon cycling while reducing CO₂emission from fossil fuel combustion. Cu‐based nanocatalysts are among the most efficient for selective CO₂‐to‐CH₃OH transformation; this conversion, however, suffers from low reactivity especially in the thermodynamically favored low temperature range. We herein report ultrasmall copper (Cu) nanocatalysts supported on crystalline, mesoporous zinc oxide nanoplate (Cu@mZnO) with notable activity and selectivity of CO₂‐to‐CH₃OH in the low temperature range of 200–250 °C. Cu@mZnO nanoplates are prepared based on the crystal‐crystal transition of mixed Cu and Zn basic carbonates to mesoporous metal oxides and subsequent hydrogen reduction. Under the nanoconfinement of mesopores in crystalline ZnO frameworks, ultrasmall Cu nanoparticles with an average diameter of 2.5 nm are produced. Cu@mZnO catalysts have a peak CH₃OH formation rate of 1.13 mol h⁻¹per 1 kg under ambient pressure at 246 °C, about 25 °C lower as compared to that of the benchmark catalyst of Cu−Zn−Al oxides. Our new synthetic strategy sheds some valuable insights into the design of porous catalysts for the important conversion of CO₂‐to‐CH₃OH. 

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2. Dual-site catalysts featuring platinum-group-metal atoms on copper shapes boost hydrocarbon formations in electrocatalytic CO2 reduction

   https://doi.org/10.1038/s41467-023-38777-y  

   Chhetri, Manjeet; Wan, Mingyu; Jin, Zehua; Yeager, John; Sandor, Case; Rapp, Conner; Wang, Hui; Lee, Sungsik; Bodenschatz, Cameron J.; Zachman, Michael J.; et al (December 2023, Nature Communications)

   Abstract Copper-based catalyst is uniquely positioned to catalyze the hydrocarbon formations through electrochemical CO₂reduction. The catalyst design freedom is limited for alloying copper with H-affinitive elements represented by platinum group metals because the latter would easily drive the hydrogen evolution reaction to override CO₂reduction. We report an adept design of anchoring atomically dispersed platinum group metal species on both polycrystalline and shape-controlled Cu catalysts, which now promote targeted CO₂reduction reaction while frustrating the undesired hydrogen evolution reaction. Notably, alloys with similar metal formulations but comprising small platinum or palladium clusters would fail this objective. With an appreciable amount of CO-Pd₁moieties on copper surfaces, facile CO^*hydrogenation to CHO^*or CO-CHO^*coupling is now viable as one of the main pathways on Cu(111) or Cu(100) to selectively produce CH₄or C₂H₄through Pd-Cu dual-site pathways. The work broadens copper alloying choices for CO₂reduction in aqueous phases. 

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3. Insights into how the aqueous environment influences the kinetics and mechanisms of heterogeneously-catalyzed COH* and CH ₃ OH* dehydrogenation reactions on Pt(111)

   https://doi.org/10.1039/C9CP00824A  

   Bodenschatz, Cameron J.; Xie, Tianjun; Zhang, Xiaohong; Getman, Rachel B. (May 2019, Physical Chemistry Chemical Physics)

   Water influences catalytic reactions in multiple ways, including energetic and mechanistic effects. While simulations have provided significant insight into the roles that H 2 O molecules play in aqueous-phase heterogeneous catalysis, questions still remain as to the extent to which H 2 O structures influence catalytic mechanisms. Specifically, influences of the configurational variability in the water structures at the catalyst interface are yet to be understood. Configurational variability is challenging to capture, as it requires multiscale approaches. Herein, we apply a multiscale sampling approach to calculate reaction thermodynamics and kinetics for COH* dehydrogenation to CO* and CH 3 OH* dehydrogenation to CH 2 OH* on Pt(111) catalysts under liquid H 2 O. We explore various pathways for these dehydrogenation reactions that could influence the overall mechanism of methanol decomposition by including participation of H 2 O structures both energetically and mechanistically. We find that the liquid H 2 O environment significantly influences the mechanism of COH* dehydrogenation to CO* but leaves the mechanism of CH 3 OH* dehydrogenation to CH 2 OH* largely unaltered. 

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4. A chemical dynamics study of the reaction of the methylidyne radical (CH, X ² Π) with dimethylacetylene (CH ₃ CCCH ₃ , X ¹ A _1g )

   https://doi.org/10.1039/D1CP04443E  

   He, Chao; Fujioka, Kazuumi; Nikolayev, Anatoliy A.; Zhao, Long; Doddipatla, Srinivas; Azyazov, Valeriy N.; Mebel, Alexander M.; Sun, Rui; Kaiser, Ralf I. (December 2021, Physical Chemistry Chemical Physics)

   The gas-phase reaction of the methylidyne (CH; X 2 Π) radical with dimethylacetylene (CH 3 CCCH 3 ; X 1 A 1g ) was studied at a collision energy of 20.6 kJ mol −1 under single collision conditions with experimental results merged with ab initio calculations of the potential energy surface (PES) and ab initio molecule dynamics (AIMD) simulations. The crossed molecular beam experiment reveals that the reaction proceeds barrierless via indirect scattering dynamics through long-lived C 5 H 7 reaction intermediate(s) ultimately dissociating to C 5 H 6 isomers along with atomic hydrogen with atomic hydrogen predominantly released from the methyl groups as verified by replacing the methylidyne with the D1-methylidyne reactant. AIMD simulations reveal that the reaction dynamics are statistical leading predominantly to p28 (1-methyl-3-methylenecyclopropene, 13%) and p8 (1-penten-3-yne, 81%) plus atomic hydrogen with a significant amount of available energy being channeled into the internal excitation of the polyatomic reaction products. The dynamics are controlled by addition to the carbon–carbon triple bond with the reaction intermediates eventually eliminating a hydrogen atom from the methyl groups of the dimethylacetylene reactant forming 1-methyl-3-methylenecyclopropene (p28). The dominating pathways reveal an unexpected insertion of methylidyne into one of the six carbon–hydrogen single bonds of the methyl groups of dimethylacetylene leading to the acyclic intermediate, which then decomposes to 1-penten-3-yne (p8). Therefore, the methyl groups of dimethylacetylene effectively ‘screen’ the carbon–carbon triple bond from being attacked by addition thus directing the dynamics to an insertion process as seen exclusively in the reaction of methylidyne with ethane (C 2 H 6 ) forming propylene (CH 3 C 2 H 3 ). Therefore, driven by the screening of the triple bond, one propynyl moiety (CH 3 CC) acts in four out of five trajectories as a spectator thus driving an unexpected, but dominating chemistry in analogy to the methylidyne – ethane system. 

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5. Modelling methanol and hydride formation in the JWST Ice Age era

   https://doi.org/10.1051/0004-6361/202452389  

   Jiménez-Serra, Izaskun; Megías, Andrés; Salaris, Joseph; Cuppen, Herma; Taillard, Angèle; Jin, Miwha; Wakelam, Valentine; Vasyunin, Anton I; Caselli, Paola; Pendleton, Yvonne J; et al (March 2025, Astronomy & Astrophysics)

   Context.Recent JWST observations have measured the ice chemical composition towards two highly extinguished background stars, NIR38 and J110621, in the Chamaeleon I molecular cloud. The observed excess of extinction on the long-wavelength side of the H₂O ice band at 3 μm has been attributed to a mixture of CH₃OH with ammonia hydrates NH₃·H₂O), which suggests that CH₃OH ice in this cloud could have formed in a water-rich environment with little CO depletion. Laboratory experiments and quantum chemical calculations suggest that CH₃OH could form via the grain surface reactions CH₃+ OH and/or C + H₂O in water-rich ices. However, no dedicated chemical modelling has been carried out thus far to test their efficiency. In addition, it remains unexplored how the efficiencies of the proposed mechanisms depend on the astrochemical code employed. Aims.We modelled the ice chemistry in the Chamaeleon I cloud to establish the dominant formation processes of CH₃OH, CO, CO₂, and of the hydrides CH₄and NH₃(in addition to H₂O). By using a set of state-of-the-art astrochemical codes (MAGICKAL, MONACO, Nautilus, UCLCHEM, and KMC simulations), we can test the effects of the different code architectures (rate equation vs. stochastic codes) and of the assumed ice chemistry (diffusive vs. non-diffusive). Methods.We consider a grid of models with different gas densities, dust temperatures, visual extinctions, and cloud-collapse length scales. In addition to the successive hydrogenation of CO, the codes’ chemical networks have been augmented to include the alternative processes for CH₃OH ice formation in water-rich environments (i.e. the reactions CH₃+ OH → CH₃OH and C + H₂O → H₂CO). Results.Our models show that the JWST ice observations are better reproduced for gas densities ≥10⁵cm⁻³and collapse timescales ≥10⁵yr. CH₃OH ice formation occurs predominantly (>99%) via CO hydrogenation. The contribution of reactions CH₃+ OH and C + H₂O is negligible. The CO₂ice may form either via CO + OH or CO + O depending on the code. However, KMC simulations reveal that both mechanisms are efficient despite the low rate of the CO + O surface reaction. CH₄is largely underproduced for all codes except for UCLCHEM, for which a higher amount of atomic C is available during the translucent cloud phase of the models. Large differences in the predicted abundances are found at very low dust temperatures (T_dust<12 K) between diffusive and non-diffusive chemistry codes. This is due to the fact that non-diffusive chemistry takes over diffusive chemistry at such low T_dust. This could explain the rather constant ice chemical composition found in Chamaeleon I and other dense cores despite the different visual extinctions probed. 

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