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Production of formic acid (FA) by hydrogenation of CO2 using a ternary hybrid catalyst, poly(ethyleneimine)-tethered Ir-iminophosphine complex (Ir-PN-PEI) immobilized in titanate nanotubes (TNTs), is reported. On the basis of comprehensive structural analyses, we show that Ir-PN-PEI is tightly immobilized within the cavity space of TNT without affecting the electronic/coordination states of Ir atoms. Liquid-phase CO2 hydrogenation under pressurized CO2 and H2 demonstrates that the Ir-PN-PEI catalyst immobilized in Na+-type TNT exhibits the highest FA yields (TON>1000 for 20 h under mild reaction conditions (2.0 MPa, 140 °C)) and improved reusability, which far outperform those of unimmobilized prototype Ir-PN-PEI. The improved catalytic performance is attributed to the ability of TNT to efficiently capture CO2 and to stabilize PEI, with Na+-type TNT with higher basic property providing a more productive effect. The catalyst is reusable over multiple cycles with activity comparable to those of heterogeneous catalysts previously reported, rendering this material suitable for efficient transformation of CO2 into FA. [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]

[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]

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]

The Front Cover shows the production of formic acid from CO2 and H2 by a ternary hybrid catalyst composed of an Ir complex, poly(ethyleneimine) and titanate nanotubes (TNTs).In their Full Paper, Y. Kuwahara et al. demonstrate that immobilization of a poly(ethyleneimine)‐tethered Ir complex catalyst inside the cavity space of TNTs can afford efficient catalysts with both improved activity and reusability, owing to the CO2 adsorption capacity of poly(ethyleneimine) and stabilizing effect of TNTs. This study can potentially offer a generalized method to capture and convert CO2, which is particularly desirable for sustainable formic acid production. More information can be found in the Full Paper by Y. Kuwahara et al. on page 1906 in Issue 11, 2017 (DOI: 10.1002/cctc.201700508). [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]

Graphical abstract Highlights • Pd/N-doped carbon xerogels for the formic acid dehydrogenation were synthetized. • The effect of pore texture and N content was investigated. • The presence of N-functionalities is beneficial for the final catalytic activity. • An initial TOF value of 2014 h−1 on the basis of the total Pd loading was obtained. Abstract N-doped carbon xerogels synthesized from melamine-resorcinol-formaldehyde aqueous gels were used as supports for the preparation of Pd-based catalysts for the formic acid dehydrogenation reaction. The effect of the pore texture and nitrogen content of the carbon xerogels on the catalytic activity for the hydrogen production was investigated. It was observed that an appropriate nitrogen doping in a well-defined micro-mesoporous carbon xerogel enables the preparation of Pd catalysts with appreciable catalytic enhancement towards the formic acid dehydrogenation as compared to the N-free counterpart, reaching an initial TOF value of 2014 h−1. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The importance of H 2 in the renewable and pollutant-free energy scenario is pointed out. • Synthetic strategies of N-doped carbon materials and related catalysts are summarized. • HCOOH, NH 3 BH 3 and H 2 O are exemplified as hydrogen molecular carriers. • N-functionalities play a key role in attaining highly performing catalysts for H 2 production. Abstract Nitrogen-doped carbon materials have emerged as versatile candidates with outstanding features as both support of metal-based catalysts and metal-free catalytic systems. Their use has been traditionally linked to electrochemical applications, but the number of applications in which these materials show their virtues has been exponentially increasing in the last decade. Particularly, catalysts based on metal nanoparticles supported on nitrogen-doped carbon materials have shown to be attractive for important catalytic reactions as they display enhanced performances endowed by well-dispersed, stabilized and electronically promoted nanoparticles as well as by the modified acid-base properties of the support. The present review is focused on the most recent breakthroughs achieved by these catalytic systems in the hydrogen production from some of the most representative hydrogen carrier molecules by highlighting the effect of the incorporation of nitrogen in the support matrix. [ABSTRACT FROM AUTHOR]

In recent years, research on the use of surface plasmon resonance phenomena induced by visible to near-infrared light for photocatalytic reactions has attracted much attention from the viewpoint of solar energy utilization. It has been extensively researched that the plasmon-mediated catalytic reaction can be promoted due to the injection of energetic hot electrons originating during the relaxation process of the surface plasmon resonance (SPR) into the reaction substrate molecules. In this report, we have prepared Pd/Au NRs@rGO nanocatalyst in which Au nanorods (NRs) with plasmonic properties are surrounded by a layer of reduced graphene oxide (rGO) with excellent electrical conductivity, and Pd nanoparticles (NPs) are supported on the Au NRs to efficiently transport hot electrons to the reaction substrate. The successful synthesis of the catalyst was characterized by HAADF-STEM, TEM, UV–vis, XRD, XAFS, and ICP analysis. The applicability of the prepared catalyst was tested in the photocatalytic reduction of CO 2 to formic acid (FA) reaction under visible light irradiation. A photocatalytic FA yield of 1.7 μmol was obtained in 24 h, which was 2.7-fold higher than in dark reaction conditions. The SPR enhancement of Pd/Au NRs in combination with rGO in Pd/Au NRs@rGO catalyst led to the superior product yield of FA under visible light irradiation and room temperature conditions. [Display omitted] • Au NR-based plasmonic catalyst in combination with Pd-rGO nanohybrid was designed. • Photocatalytic hydrogenation of CO 2 to formic acid was employed as the test reaction. • Promotional effect in the product formation was observed due to the SPR of Au NRs. [ABSTRACT FROM AUTHOR]