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Aerobic oxidative dehydrogenation of amines to imines by thiol‐modified Pd nanoparticle (NP) catalysts on carbon supports is reported herein. Whereas conventional non‐modified Pd NP catalysts are nearly inactive, the carbon‐supported Pd catalysts modified with thiol ligands efficiently catalyze the reaction with high selectivity. Kinetic studies and DFT calculations reveal that the rate‐limiting imine product desorption step is significantly boosted on the thiol ligands‐modified Pd surface compared to the non‐modified Pd surface due to the steric hindrance of the ligands. Furthermore, the catalytic activity is dramatically enhanced in the presence of both pyrene‐functionalized thiol modifiers and graphene‐based carbon supports; 96 % conversion is attained after 4 h at 110 °C. The π–π interactions between pyrene groups and the highly crystallized carbon surface suppress the leaching of ligands, which offers improved catalyst stability even under O2 atmosphere at 110 °C, thereby resulting in high activity. [ABSTRACT FROM AUTHOR]

Pd nanoparticles (NPs) supported on Ti-doped graphitic carbon nitride (g-C3N4) were synthesized by a deposition-precipitation route and a subsequent reduction with NaBH4. The features of the NPs were studied by XRD, TEM, FTIR, XPS, EXAFS and N2-physisorption measurements. It was found that the NPs had an average size of 2.9 nm and presented a high dispersion on the surface of Ti-doped g-C3N4. Compared to Pd loaded on pristine g-C3N4, the Pd NPs supported on Ti-doped g-C3N4 exhibited a high catalytic activity in formic acid dehydrogenation in water at room temperature. The enhanced activity could be attributed to the small Pd NPs size, as well as the strong interaction between Pd NPs and Ti-doped g-C3N4. [ABSTRACT FROM AUTHOR]

In this study, monometallic gold and palladium, and bimetallic gold/palladium were respectively deposited on chromium based amine-functionalized metal-organic framework (NH-MIL-101) by using the impregnation method, with the aim to enhance the activity of Pd-catalyzed chemical reaction under the assistance of visible light at ambient temperatures. The oxidation state, size and location of metal nanoparticles were determined by XAFS and TEM. The physical properties of as-synthesized catalysts were also well characterized by UV-vis spectroscopy, BET and XRD. The catalytic activities of those metal nanoparticles deposited MOFs were studies for hydrolysis of ammonia borane and Suzuki-Miyaura coupling reaction. Compared with monometallic counterpart, the bimetallic gold/palladium showed much higher catalytic activity for hydrolysis of ammonia borane and Suzuki-Miyaura coupling reaction under visible light irradiation. The enhancement of the catalytic activity might be attributed to the synergistic effect between plasmonic bimetallic nanoparticles and metal organic framework in effective conversion of solar energy for generating electron rich palladium species to activate the electrophilic compounds as well as nucleophilic partner compounds. This investigation offers a new opportunity to explore the high-performance metal nanoparticle loaded MOFs photocatalysts for efficient utilization of sunlight in a wide range of chemical reactions. [ABSTRACT FROM AUTHOR]

Metal-support interactions (MSIs) and particle size play important roles in catalytic reactions. For the first time, silver nanoparticles supported on CeO2-SBA-15 supports are reported that possess tunable particle size and MSIs, as prepared by microwave (MW) irradiation, owing to strong charge polarization of CeO2 clusters (i.e., MW absorption). Characterizations, including TEM, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure, were carried out to disclose the influence of CeO2 contents on the Ag particle size, MSI effect between Ag nanoparticles and CeO2-SBA-15 supports, and the strong MW absorption of CeO2 clusters that contribute to the MSIs during Ag deposition. The Ag particle sizes were controllably tuned from 1.9 to 3.9 nm by changing the loading amounts of CeO2 from 0.5 to 2.0 wt %. The Ag nanoparticle size was predominantly responsible for the high turnover frequency (TOF) of 0.41 min−1 in ammonia borane dehydrogenation, whereas both particle size and MSIs contributed to the high TOF of 555 min−1 in 4-nitrophenol reduction for Ag/0.5CeO2-SBA-15, which were twice as large as those of Ag/SBA-15 without CeO2 and Ag/CeO2-SBA-15 prepared by conventional oil-bath heating. [ABSTRACT FROM AUTHOR]

Levulinic acid is considered one of the most important biomass-derived chemicals owing to its potential as a versatile building block to synthesize valuable fuels and chemicals. Levulinate esters, such as methyl levulinate and ethyl levulinate obtained via esterification of levulinic acid with alcohols, can in particular be used as fuel additives and plasticizers, and thus have a potential to replace a significant amount of petroleum-derived chemical feedstocks. In this article, sulfated zirconosilicates having P6mm hexagonal mesoporous structure were applied as solid acid catalysts to the esterification of levulinic acid with ethanol to produce ethyl levulinate, and the influences of preparation conditions on the structural properties and catalytic performances were investigated. A distinct correlation was observed between the catalytic activity and the density of acid sites, showing that dispersibility of the acid sites and the associated accessibility of the organic reactants play an important role in determining the overall activity. Among the catalysts tested, sulfated Zr–SBA-15 with optimum Zr content (Si/Zr ratio of 10.7) was found to be the best catalyst, the activity of which was far superior to that of conventional sulfated ZrO 2 . In addition, direct conversion of cellulosic sugars (glucose and fructose) into levulinate esters was also examined. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrogenation of CO 2 to formic acid with Pd-based catalyst has been reviewed. • Effect of PdM alloys and N functionalities on the catalytic activity was elucidated. • Successful strategies to maximize the performance catalytic activity were assessed. • Challenges and future directions in the hydrogenation of CO 2 discussed in the end. The "greenhouse effect" caused by presence of the large amounts of carbon dioxide (CO 2) is becoming extremely serious for the environment. Therefore, it is crucial to advance the progress of practical technologies to minimize the CO 2 emissions. The catalytic CO 2 hydrogenation with hydrogen (H 2) to form formic acid/formate over Pd-based catalysts has been considered as an effective technology to deal with environment and CO 2 emission issues. In the past decades, increasing efforts have been contributed to these fields and significant achievements have been obtained. In this review, the state-of-the-art of Pd-based heterogenous catalysts for catalytic conversion of CO 2 to formate/formic acid is systematically summarized. First, the key factors associated with catalytic performance are discussed including Pd metal dispersion, electron density of Pd metal and acidity of supports. Second, major achievements on the design of efficient Pd nanometal supported on various materials, mainly metal-organic frameworks (MOFs), carbon materials, silica, zeolites and other porous material, are summarized. Third, the successful strategies applied to maximize catalytic activity of CO 2 conversion by reducing the particle size of Pd, alloying foreign metal with Pd to change the electron density of Pd, as well as anchoring of functional groups were also highlighted. Special attention has been given to the mechanism of the catalytic reaction. Finally, a brief perspective to the challenges and new directions in the development of innovative catalytic materials to achieve high catalytic activity in CO 2 conversion is also proposed, which would be of great interest in realizing carbon-neutrality in near future. [ABSTRACT FROM AUTHOR]

[Display omitted] • Core–shell-structured nanocomposite photocatalysts were designed and synthesized. • Single-site Co species were immobilized into g-C 3 N 4 via a simple pyrolysis process. • Co-doped g-C 3 N 4 coats the surface of Au nanorods via electrostatic self-assembly. • Surface plasmon resonance of Au promoted CO production on single-site Co species. • The core–shell structure is key to achieving high activity in the plasmonic catalysis. Designing efficient photocatalyst materials for CO 2 reduction and utilization has become important to address environmental and energy concerns. A new type of core–shell-structured nanocomposite catalyst is reported herein, in which single-site Co catalytic species are immobilized in graphitic carbon nitride (g-C 3 N 4) layered on Au nanorods (NRs) for surface plasmon resonance (SPR)-enhanced photocatalytic CO 2 conversion. Single-site Co species were incorporated into g-C 3 N 4 via a simple pyrolysis process, and core–shell nanocomposites were self-formed via electrostatic interactions between the positively charged surfaces of the Au NRs and negatively charged single-site Co-coordinated g-C 3 N 4 layer. The structure was comprehensively examined by TEM, XRD, UV–vis, Co K-edge XAFS, FT-IR, and zeta potential measurements, which showed that the g-C 3 N 4 layer did not prevent the Au NRs from absorbing visible light. The nanocomposite efficiently catalyzed the reduction of CO 2 to CO under visible light irradiation with the assistance of the SPR of the Au NRs. The catalytic activity of the core–shell-structured catalyst was superior to that of the corresponding aggregated catalyst, demonstrating that the formation of a core–shell structure affords efficient electron transport from the Au NRs to the catalytically active Co species. [ABSTRACT FROM AUTHOR]

Formic acid (FA; HCOOH) is one of the most promising candidates for the storage of hydrogen (H2). Herein, we report a H2 storage/production system based on the hydrogenation of CO2 and dehydrogenation of FA, using a nanostructured heterogeneous catalyst. Pd1Ag2 nanoparticles with an average size of 2.8 nm were encapsulated within a zeolitic imidazolate framework (ZIF-8) having a core-shell structure (ZIF-8@Pd1Ag2@ZIF-8). This composite displayed high activity and stability during both the hydrogenation of CO2 to produce FA and the dehydrogenation of FA into H2 and CO2. This improved performance is attributed to the use of ultrafine Pd1Ag2 nanoparticles as well as the spatial regulation of the nanoparticles within the reaction field. This study suggests a new strategy for controlling the spatial distribution of metal nanoparticles within MOFs so as to fine-tune the catalytic activity and selectivity of ZIF-8@metal nanoparticles@ZIF-8 catalysts. [ABSTRACT FROM AUTHOR]

• Lanthanum Strontium Cobalt (LSC) perovskites were prepared by sol-gel method. • Doped-LSC perovskites were assessed in ammonia borane decomposition. • The closer interaction Cu-Co might be favoring the catalytic activity. • Cu doping was found to be a good option to boost the catalytic activity. Lanthanum Strontium Cobalt (LSC) perovskite-based catalysts were prepared and evaluated in the ammonia borane dehydrogenation reaction. Doping with additional non-noble metals, such as Ni or Cu greatly enhanced the catalytic performance, especially in the case of Cu. In order to evaluate the effect of the Cu loading, catalysts with various Cu contents ranging from 0.82 to 5.42 wt.% were synthesized. It was found that the Cu-doped sample with a nominal formula of La 0.7 Sr 0.3 Co 0.90 Cu 0.10 O 3 containing 2.72 wt.% of Cu displayed the highest catalytic activity among investigated, which outperformed the counterpart Cu-supported catalyst (Cu/La 0.7 Sr 0.3 CoO 3). La 0.7 Sr 0.3 Co 0.90 Cu 0.10 O 3 showed good durability during five consecutive reaction runs, confirming the suitability of perovskite-type catalysts in stabilizing the catalytic active phase. The present catalytic system provides a cost-effective alternative to the noble-metal-based catalysts commonly used to catalyze the ammonia borane dehydrogenation reaction. [ABSTRACT FROM AUTHOR]

Carbon/g-C 3 N 4 composites (C/g-C 3 N 4 ) with various carbon contents have been prepared by a simple experimental protocol from glucose and dicyandiamide. The results of the characterization of the as-prepared materials indicated that the skeleton structure of g-C 3 N 4 was not altered upon formation of the composite supports and the resulting composites showed a gradual increasing light harvesting capability with the carbon content. Ru-supported catalysts were synthesized from C/g-C 3 N 4 and assessed in the ammonia borane dehydrogenation reaction under dark and visible light irradiation conditions. The enhanced performance displayed by Ru/C/g-C 3 N 4 photocatalysts as compared to Ru/g-C 3 N 4 counterpart might be the result of the effect of the addition of carbon in dispersing and stabilizing small Ru nanoparticles and enhancing the optical absorption properties. [ABSTRACT FROM AUTHOR]

This work presents the synthesis of Pd-loaded microporous titanosilicalite-1 (Pd/TS-1) and Pd-loaded hierarchical titanosilicalite-1 (Pd/HTS-1) with abundant mesopores (2–30 nm) inside the framework via hydrothermal method using polydiallydimethyl ammonium chloride as the non-surfactant mesopore template. XRD, N 2 sorption, FT-IR, FESEM-EDX, TEM, XPS, and DR-UV techniques were used to characterize the morphological and physicochemical properties of the synthesized materials. These materials were tested as heterogeneous catalysts, along with tetrapropylammonium bromide as co-catalyst, for cycloaddition reactions of CO 2 with epoxides to produce cyclic carbonates. It was found that the epoxide conversions were influenced by acidity and pore accessibility of the catalysts. Using Pd/HTS-1 facilitated bulky substrates to access active sites, resulting in higher conversions than Pd/TS-1. Over 85 % conversions were achieved for at least five consecutive cycles without significant loss in catalytic activity. The interaction between the Pd active surfaces and epichlorohydrin (ECH) was further studied by DFT calculations. The existence of Pd(200) was more influential on adsorbing epichlorohydrin (ECH) and subsequent formation of dissociated ECH (DECH) intermediate than Pd(111) surface. However, Pd(111) was dominant in enhancing the activity of DECH species for capturing CO 2. Therefore, the co-existence of Pd(200) and Pd(111) surfaces was needed for cycloaddition of CO 2 with ECH. [Display omitted] • Novel Pd/HTS-1 showed high potential for catalyzing CO 2 cycloaddition with epoxides. • Catalyst had enhanced Lewis acid sites and high accessibility to HTS-1 active sites. • Effects of Pd surface on its interaction with ECH were investigated computationally. • Pd(200) and Pd(111) surfaces were proven to promote adsorption of ECH to capture CO 2. [ABSTRACT FROM AUTHOR]

The decoration of MWCNT in Cu/TiO 2 catalyst improved the H 2 production. [Display omitted] • Photocatalysts based on transition metals supported on TiO 2 MWCNT were synthesized. • The presence of MWCNT improved the H 2 production from ammonia borane. • Cu-based photocatalysts displayed the best activity among investigated. • The catalytic activity depended on the Cu content. • Cu1%/TiO 2 -MWCNT was the most active photocatalyst. In this study, we assessed the effect of the incorporation of multi-walled carbon nanotubes (MWCNT) on a TiO 2 support containing different active metals to obtain Metal/TiO 2 -MWCNT photocatalytic systems. The materials prepared in this work were characterized by ICP-OES, TEM, EDX, XRD, PL, UV–vis, and nitrogen physisorption techniques. Among those investigated metals, Cu was shown to be the most promising for the present application. The assessment of the photocatalytic performance of Cu/TiO 2 -MWCNT with various Cu contents revealed that the catalytic activity depends on the Cu loading and the photocatalyst with 1 wt.% of Cu displayed the best performance among investigated. The incorporation of MWCNT in the support enhanced the photocatalytic activity towards the production of H 2 under visible and UV–vis light irradiation at room temperature. [ABSTRACT FROM AUTHOR]

The catalytic ability of graphitic carbon nitride (g-C 3 N 4)-supported composition-controlled PdCo catalysts towards H 2 generation from the formic acid dehydrogenation reaction was assessed in this study and a noticeable composition dependence was evidenced. It was seen that the alloying effect combined with the nitrogen functionalities present on g-C 3 N 4 assisted the formation of small and well-distributed nanoparticles. This fact, combined with the electronic promotion of Pd species via charge transfer from Co and basic features of the support, resulted in enhanced catalytic activities compared to that displayed by the counterpart Pd/g-C 3 N 4 , reaching a TOF value of 1193 h−1 for the most active catalyst among investigated (PdCo/g-C 3 N 4 (1/0.7)). Furthermore, the present catalytic system showed high selectivity towards formic acid dehydrogenation, suppressing the generation of undesired CO via formic acid dehydration, which makes it a suitable candidate for practical application in fuel cells. Image 1 • Small NPs achieved because of alloying effect and N-functionalities of the support. • Electronic promotion of Pd species via charge transfer from Co. • Activity of PdCo/g-C 3 N 4 related to the size of NP, composition and electronic state. • PdCo/g-C 3 N 4 (1/0.7) was the most active among investigated with a TOF of 1193 h−1. [ABSTRACT FROM AUTHOR]