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Supported metal single atom catalysis is a dynamic research area in catalysis science combining the advantages of homogeneous and heterogeneous catalysis. Understanding the interactions between metal single atoms and the support constitutes a challenge facing the development of such catalysts, since these interactions are essential in optimizing the catalytic performance. For conventional carbon supports, two types of surfaces can contribute to single atom stabilization: the basal planes and the prismatic surface; both of which can be decorated by defects and surface oxygen groups. To date, most studies on carbon‐supported single atom catalysts focused on nitrogen‐doped carbons, which, unlike classic carbon materials, have a fairly well‐defined chemical environment. Herein we report the synthesis, characterization and modeling of rhodium single atom catalysts supported on carbon materials presenting distinct concentrations of surface oxygen groups and basal/prismatic surface area. The influence of these parameters on the speciation of the Rh species, their coordination and ultimately on their catalytic performance in hydrogenation and hydroformylation reactions is analyzed. The results obtained show that catalysis itself is an interesting tool for the fine characterization of these materials, for which the detection of small quantities of metal clusters remains a challenge, even when combining several cutting‐edge analytical methods. [ABSTRACT FROM AUTHOR]

Single-atomic metal catalysts are attractive for green chemistry in terms of their outstanding catalytic performance and savings in precious metal usage owing to maximized metal utilization, including anode catalysts in polymer electrolyte fuel cells (PEFCs). Heteroatom-doped porous carbons are extensively used as supports, where the heteroatoms contribute to the immobilization of single-atomic metals. However, high-content doping of heteroatoms, especially sulphur (S), into carbon supports is still challenging because S species can be readily desorbed during heat treatment. Herein, we present a bottom-up fabrication approach for S-rich porous carbons from molecular precursors via a thermal polymerization process. A simple carbonization of molecules with thermally stable S-containing building blocks and polymerizable ethynyl moieties at 900 °C yields microporous carbon materials with record-high S content (over 15 wt%). The abundant S species function as an effective anchoring site for single-atomic platinum (Pt) species. Toward anode catalysts in PEFCs, the prepared single-atomic Pt catalysts efficiently promote the electrochemical hydrogen oxidation reaction, whose activity is comparable to that of commercial Pt/C, despite the significantly low Pt loading amount. [ABSTRACT FROM AUTHOR]

Template-assisted chemical vapor deposition (CVD) is a promising approach for fabricating nanoporous materials based on graphene walls. Among conventional metal oxide templates, CaO, produced through the thermal decomposition of CaCO3, offers improved environmental sustainability and lower production costs, thereby potentially making it a viable candidate for green template materials. Nevertheless, the underlying reaction mechanisms of the interaction on the CaO surface during the CVD process remain indeterminate, giving rise to challenges in regulating graphene formation and obtaining high-quality materials. In this work, a comprehensive experimental–theoretical investigation has unveiled the CVD mechanism on CaO. CaO exhibits efficient catalytic activity in the dissociation of CH4, thereby facilitating a thermodynamically favorable conversion of CH4 to graphene. These findings highlight the potential of using CaO as a substrate for graphene growth, combining both sustainability and cost-effectiveness. When the shell-like graphene layer deposited on CaO particles is released through the dissolution of CaO with HCl, the resulting nanoporous graphene-based materials can be readily compacted by the capillary force of the liquid upon drying. The folded surfaces, however, can become available for electric double-layer capacitance via electrochemical exfoliation under a low applied potential (<1.2 V vs. Ag/AgClO4). [ABSTRACT FROM AUTHOR]

Although lithium–oxygen batteries have attracted attention due to their extremely high energy densities, rational design, and critical evaluation of high‐energy‐density cathode for practical Li–O2 batteries is still urgently needed. Herein, the multiscale, angstrom‐to‐millimeter, precisely controllable synthesis of binder‐free cathodes with minimally stacked graphene free from edge sites is demonstrated. The proposed Li–O2 battery, based on a hierarchically porous cathode with a practical mass loading of >4.0 mg cm−2, simultaneously exhibits an unprecedented specific areal (>30.0 mAh cm−2), mass (>6300 mAh g−1), and volumetric (>480 mAh cm−3) capacities. The battery displays the optimal energy density of 793 Wh kg−1 critically normalized to the total mass of all active materials including electrolytes and even discharge products Li2O2. Comprehensive in situ characterizations demonstrate a unique discharge mechanism in hierarchical pores which contributes to competitive battery performance. Superior rate performance in a current density range of 0.1 to 0.8 mA cm−2 and long‐cycle stability (>260 cycles) at a current density of 0.4 mA cm−2, outperforming state‐of‐the‐art carbon cathodes. This study yields insight into next‐generation carbon cathodes, not only for use in practical Li–O2 batteries, but also in other metal–gas batteries with high energy densities. [ABSTRACT FROM AUTHOR]

The rational design of a stable and catalytic carbon cathode is crucial for the development of rechargeable lithium‐oxygen (LiO2) batteries. An edge‐site‐free and topological‐defect‐rich graphene‐based material is proposed as a pure carbon cathode that drastically improves LiO2 battery performance, even in the absence of extra catalysts and mediators. The proposed graphene‐based material is synthesized using the advanced template technique coupled with high‐temperature annealing at 1800 °C. The material possesses an edge‐site‐free framework and mesoporosity, which is crucial to achieve excellent electrochemical stability and an ultra‐large capacity (>6700 mAh g−1). Moreover, both experimental and theoretical structural characterization demonstrates the presence of a significant number of topological defects, which are non‐hexagonal carbon rings in the graphene framework. In situ isotopic electrochemical mass spectrometry and theoretical calculations reveal the unique catalysis of topological defects in the formation of amorphous Li2O2, which may be decomposed at low potential (∼ 3.6 V versus Li/Li+) and leads to improved cycle performance. Furthermore, a flexible electrode sheet that excludes organic binders exhibits an extremely long lifetime of up to 307 cycles (>1535 h), in the absence of solid or soluble catalysts. These findings may be used to design robust carbon cathodes for LiO2 batteries. [ABSTRACT FROM AUTHOR]

Ordered carbonaceous frameworks (OCFs) are a new class of carbon materials with a three-dimensional ordered structure synthesized by simple carbonization of metalloporphyrin crystals with polymerizable moieties. Carbonization via solid-state polymerization results in the formation of graphene-based ordered frameworks in which regularly aligned single-atomic metals are embedded. These unique structural features afford molecular-level designability like organic-based frameworks together with high electrical conductivity, thermal/chemical stability, and mechanical flexibility, towards a variety of applications including electrocatalysis and force-driven phase transition. This feature article summarizes the synthetic strategies and characteristics of OCFs in comparison with conventional organic-based frameworks and porous carbons, to discuss the potential applications and further development of the OCF family. [ABSTRACT FROM AUTHOR]

Graphene mesosponge (GMS) is a new class of mesoporous carbon consisting mainly of single-layer graphene walls. GMS has traditionally been synthesized via chemical vapour deposition (CVD) of methane onto a template of alumina (Al2O3) nanoparticles, which catalyses methane conversion. However, the Al2O3 template needs to be removed using costly and environmentally concerning processes such as hydrofluoric acid or concentrated base. In this work, we examine methane conversion catalysed by magnesium oxide (MgO) and utilized MgO as an alternative catalytic template. In contrast to Al2O3, a solid acid catalyst, MgO is a solid base catalyst that is also active for methane conversion into graphene sheets but dissolves easily in hydrochloric acid. We have investigated the reaction mechanism using in situ weight measurements and gas-emission analysis during CVD complemented by density functional theory calculations. We found that the pure MgO surface is activated via O-elimination with methane above 778 °C. On the activated MgO surface, methane is converted into a graphene sheet with a relatively low activation energy of 134 kJ mol−1. Once the first graphene layer is formed, the methane-to-graphene conversion rate decreases and the activation energy increases to 234 kJ mol−1, which is comparable to that reported in thermal methane-CVD on carbon. As a result of the faster growth rate of the first layer with respect to additional layers, it is easier to obtain single-graphene layers using MgO. The MgO-derived GMS has a unique combination of properties including a high surface area, developed mesopores, high oxidation resistance, significant softness and elasticity, very low bulk modulus (0.05 GPa), and force-driven reversible liquid–gas phase transition. Thus, we expect the MgO-derived GMS can be employed in a variety of applications including high-voltage supercapacitors and as a new type of heat pump based on the force-driven phase transition. [ABSTRACT FROM AUTHOR]

Force-responsive ordered carbonaceous frameworks (OCFs) are synthesized for the first time. Carbonization of Ni porphyrin monomers having eight polymerizable ethynyl groups yields OCFs with atomically dispersed divalent Ni species and developed micropores. The highest specific surface area (673 m2 g−1) among the OCFs has been achieved. The OCFs thus synthesized comprise non-stacked graphene sheets, affording a unique mechanical flexibility that enables force-driven reversible phase transition. [ABSTRACT FROM AUTHOR]

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]

Realizing accurate control of catalytically active centers on solid surfaces is one of the most essential goals in the development of functionalized heterogeneous catalysts. Controlled synthesis of carbon-supported Co catalysts from single-site to nanoparticles can be successfully achieved by the structural transformation of the deposited Co(salen) complex precursor under heat treatment. The obtained structures were characterized using techniques such as XRD, in situ XAFS, and TEM. The first decomposition of the Co(salen) complex is initiated by the dissociation of Co–O–C bonds at around 250 °C, which produces isolated single-atom Co species while retaining the Co–N–C bonds even up to 400 °C. When the heat treatment temperature exceeds 450 °C, the second decomposition of the Co–N–C bonds occurs to form Co oxide nanoclusters followed by the growth of Co NPs upon further increase of the heat treatment temperature. The single-site catalyst is highly dispersed and electronically deficient owing to the interaction with the carbon support, and shows activity and selectivity for the oxidation of ethylbenzene, as compared to the inherent Co(salen) complex and nanoparticle catalysts. [ABSTRACT FROM AUTHOR]

Keywords: Dehydrogenation; Heterogeneous catalysis; Pd nanoparticles; - interaction; Surface modification EN Dehydrogenation Heterogeneous catalysis Pd nanoparticles - interaction Surface modification 5834 5834 1 12/07/20 20201204 NES 201204 B The Front Cover b shows Pd nanoparticle catalysts modified with pyrene-thiol ligands on carbon supports for aerobic oxidative dehydrogenation of amines to imines. In their Communication, T. Yoshii et al. experimentally and theoretically demonstrate that the rate-limiting imine product desorption is boosted as a result of the steric hindrance of the ligands, and the catalytic stability is significantly improved by the - interactions between catalyst and support, which make this material an active and stable catalyst for the amine dehydrogenation reaction. Dehydrogenation, Heterogeneous catalysis, Pd nanoparticles, - interaction, Surface modification. [Extracted from the article]

Porous materials synthesized through bottom-up approaches, such as metal-organic frameworks and covalent organic frameworks, have attracted attention owing to their design flexibility for functional materials. However, achieving the chemical and thermal stability of these materials for various applications is challenging considering the reversible coordination bonds and irreversible covalent bonds in their frameworks. Thus, ordered carbonaceous frameworks (OCFs) emerge as a promising class of bottom-up materials with good periodicity, thermal and chemical stability, and electrical conductivity. However, a few OCFs have been reported owing to the limited range of precursor molecules. Herein, we designed a hexaazatrinaphthylene-based molecule with enediyne groups as a precursor molecule for synthesizing an OCF. The solid-state Bergman cyclization of enediyne groups at a low temperature formed a microporous polymer and an OCF, exhibiting redox activity and demonstrating their potential for electrochemical applications. The microporous polymer was used as an active material in sodium-ion batteries, while the OCF was used as an electrochemical capacitor. These findings illustrate the utility of the Bergman cyclization reaction for synthesizing microporous polymers and OCFs with a customizable functionality for broad applications.

Microporous molecular crystals are promising materials because of their designable porosity as well as their resistance to chemical and other stimuli. Here, we developed microporous molecular cocrystals by taking advantage of the specific interactions between porphyrins and fullerene molecules. Single-crystal X-ray diffraction analysis revealed that one nickel(II) porphyrin interacts with two fullerene molecules to form a two-dimensional honeycomb network with an eclipsed stacking mode, providing one-dimensional void channels. After the pores were activated by heat treatment or mechanical grinding, the prepared cocrystal can incorporate gas and solvent molecules reversibly while maintaining its single-crystallinity. Also, it retained its single-crystallinity in the presence of water, acid-base, or high pressure. These findings in this study expand the availability of molecular crystals based on intermolecular interactions as porous materials, which are expected to work under conditions that have not been applicable to other molecule-based porous materials., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Co-published by University of Science and Technology of China and American Chemical Society.)

Metal organic frameworks (MOFs) are a class of porous organic-inorganic crystalline materials that have attracted much attention as H 2 storage devices and catalytic supports. In this paper, the synthesis of highly-dispersed Ni nanoparticles (NPs) for the hydrogenation of olefins was achieved by employing Ni-MOF-74 as a precursor. Investigations of the structural transformation of Ni species derived from Ni-MOF-74 during heat treatment were conducted. The transformation was monitored in detail by a combination of XRD, in situ XAFS, and XPS measurements. Ni NPs prepared from Ni-MOF-74 were easily reduced by the generation of reducing gases accompanied by the decomposition of Ni-MOF-74 structures during heat treatment at over 300 °C under N 2 flow. Ni-MOF-74-300 exhibited the highest activity for the hydrogenation of 1-octene due to efficient suppression of excess agglomerated Ni species during heat treatment. Moreover, Ni-MOF-74-300 showed not only high activity for the hydrogenation of olefins but also high size-selectivity because of the selective formation of Ni NPs covered by MOFs and the MOF-derived carbonaceous layer., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)