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The selective hydrogenation of CO2 to value-added chemicals is attractive but still challenged by the high-performance catalyst. In this work, we report that gallium nitride (GaN) catalyzes the direct hydrogenation of CO2 to dimethyl ether (DME) with a CO-free selectivity of about 80%. The activity of GaN for the hydrogenation of CO2 is much higher than that for the hydrogenation of CO although the product distribution is very similar. The steady-state and transient experimental results, spectroscopic studies, and density functional theory calculations rigorously reveal that DME is produced as the primary product via the methyl and formate intermediates, which are formed over different planes of GaN with similar activation energies. This essentially differs from the traditional DME synthesis via the methanol intermediate over a hybrid catalyst. The present work offers a different catalyst capable of the direct hydrogenation of CO2 to DME and thus enriches the chemistry for CO2 transformations. The conversion of CO2 to valuable chemicals is still challenged by catalyst developments. Herein, the authors found that GaN is an efficient catalyst for selective CO2 hydrogenation to dimethyl ether as the primary product, in contrast to the traditional methanol-intermediate route over hybrid catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of SA-FLP dual-active-site catalysts are designed for the conversion of CH 4 and CO 2 to acetic acid. • The SA-FLP dual active sites can concurrently adsorb and activate CH 4 and CO 2. • Ag 1 -FLP catalyst exhibits the best performance in the reaction of CH 4 and CO 2 to acetic acid. Direct conversion of CH 4 and CO 2 into acetic acid is an emerging attractive process but remains a significant challenge due to the inherent stability of both molecules. Hence, developing active and stable catalysts is crucial for the simultaneous activation of CO 2 and CH 4. Herein, we designed the "Single-Atom" - "Frustrated-Lewis-Pair" (SA-FLP) dual-active-site catalysts for the co-conversion of CH 4 and CO 2 to acetic acid based on density functional theory (DFT) calculations. The SA sites were introduced by doping the transition-metal (TM) atoms (TM = Fe, Co, Ni, Cu; Ru, Rh, Pd, Ag; Os, Ir, Pt, Au) into CeO 2 (1 1 0) surface, and the FLP sites were constructed by the regulation of surface oxygen vacancies. Our results demonstrate the introduction of SA into CeO 2 surface could facilitate the formation of oxygen vacancies, and thus promotes the formation of FLP sites. The SA-FLP dual active sites can concurrently activate CH 4 and CO 2 with CH 4 preferentially activated at SA sites and CO 2 preferentially activated at FLP sites. Among the twelve SA-FLP catalysts, Ag 1 -FLP catalyst exhibits the best performance in the reaction of CH 4 and CO 2 to acetic acid with a rate-determining barrier of 1.12 eV and a turnover frequency of 2.52 × 10–3 s−1 at 573 K and 2 bar. This work not only offers a novel catalyst prototype for the co-conversion of CH 4 and CO 2 to acetic acid but also provides insights into developing dual-active-site catalysts on earth-abundant metal oxide materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ionic liquid was chemically bonded to mesoporous HAP. • High utilization of hydroxyl binding (90 %) produced high ILs loading (0.468 mmol/g). • High yield (98.7%) and high selectivity (100%) of propylene carbonate (PC). • Autocatalysis was found in the CO 2 fixed reaction. In this study, hydroxyapatite (HAP) with abundant surface hydroxyl and large pores was used as the ionic liquid ([DMCA]X) immobilization carrier, where the surface hydroxyl groups of HAP were used as binding sites and the n-halogen-acids were used as bonding agents. The supported ionic liquid catalysts [DMCA]X-n-HAP were characterized by XRD, TEM, TG and FTIR, proving that the ionic liquids were successfully bonded onto the surface of HAP. The utilization of hydroxyl sites on the surface of HAP was as high as 90%. The above catalysts were used to catalyze the cycloaddition reaction of CO 2 and propylene oxide (PO), and the yield and selectivity of propylene carbonate (PC) were up to 98.7% and 100%, respectively. The length effect of the bonding agents on the catalyst performance was also studied, and found that n-chlorine-butyric acid was the most suitable chemical for channel structure of HAP and spatial freedom of ionic liquid. In addition, the effects of halogen anion and hydroxyl hydrogen on the performance of the reaction were also studied. Importantly, autocatalysis was discovered in the reaction. Finally, the reaction intermediates and reaction mechanism of CO 2 cycloaddition were investigated by in situ -DRIFTS, revealing that ring-open of PO is rate-determining step. [ABSTRACT FROM AUTHOR]

The effect of ZrO 2 crystalline phases on Pd/ZrO 2 for catalytic combustion of toluene was investigated. It was found that Pd/t-ZrO 2 showed superior activity when the toluene concentration was lower than 2000 ppm, while Pd/m-ZrO 2 performed better with toluene concentration higher than 3000 ppm. Kinetic studies showed that the reaction order of toluene on Pd/t-ZrO 2 and Pd/m-ZrO 2 is 0 and 2, respectively. The catalytic activity was controlled by combined effect of PdO activity and quantity, which was correlated with the interaction between palladium and zirconia. The t-ZrO 2 increased PdO species activity, while m-ZrO 2 could enhance the amount of PdO. DFT results showed that the p-band center of the O of PdO on t-ZrO 2 was higher, suggesting that PdO was more active. In situ -DRIFTS revealed that the reaction pathway of catalytic oxidation of toluene on Pd/ZrO 2 was as follows: toluene was oxidized stepwise to benzyl alcohol, benzaldehyde, benzoic acid, CO 2 and H 2 O. [Display omitted] • Effect of Pd/ZrO 2 with different ZrO 2 crystal types for toluene combustion. • Catalytic activity was controlled by the comprehensive effect between PdO activity and PdO quantity. • The reaction order of toluene on Pd/t-ZrO 2 and Pd/m-ZrO 2 is 0 and 2, respectively. • Desorption energies of O atoms in O-Pd/m-ZrO 2 and O-P/t-ZrO 2. • The reaction pathway of catalytic combustion of toluene on Pd/ZrO 2 catalysts. [ABSTRACT FROM AUTHOR]