The use of formic acid (FA) to produce molecular H2 is a promising means of efficient energy storage in a fuel‐cell‐based hydrogen economy. To date, there has been a lack of heterogeneous catalyst ...systems that are sufficiently active, selective, and stable for clean H2 production by FA decomposition at room temperature. For the first time, we report that flexible pyridinic‐N‐doped carbon hybrids as support materials can significantly boost the efficiency of palladium nanoparticle for H2 generation; this is due to prominent surface electronic modulation. Under mild conditions, the optimized engineered Pd/CN0.25 catalyst exhibited high performance in both FA dehydrogenation (achieving almost full conversion, and a turnover frequency of 5530 h−1 at 25 °C) and the reversible process of CO2 hydrogenation into FA. This system can lead to a full carbon‐neutral energy cycle.
Pyridinic‐N‐tuned catalysis: An electron‐rich pyridinic‐N dopant modulates the electronic interactions between the active sites of palladium nanoparticles and the carbon support. Formic acid dehydrogenation at room temperature is significantly boosted by the pyridinic‐N‐doped palladium catalyst, presenting an efficient and reliable route to clean H2 generation and sustainable energy storage.
The formate‐based rechargeable hydrogen battery (RHB) promises high reversible capacity to meet the need for safe, reliable, and sustainable H2 storage used in fuel cell applications. Described ...herein is an additive‐free RHB which is based on repetitive cycles operated between aqueous formate dehydrogenation (discharging) and bicarbonate hydrogenation (charging). Key to this truly efficient and durable H2 handling system is the use of highly strained Pd nanoparticles anchored on graphite oxide nanosheets as a robust and efficient solid catalyst, which can facilitate both the discharging and charging processes in a reversible and highly facile manner. Up to six repeated discharging/charging cycles can be performed without noticeable degradation in the storage capacity.
The formate/bicarbonate pair: A rechargeable hydrogen battery based on repetitive formate/bicarbonate interconversion in aqueous solution was developed. A hybrid material of Pd nanoparticles and reduced graphite oxide serves as the robust and efficient catalyst for both steps. Multiple charging and discharging cycles were performed with comparable storage/release efficiency and the resulting H2 gas is free of CO and CO2.
The azo linkage is a prominent chemical motif which has found numerous applications in materials science, pharmaceuticals, and agrochemicals. Described herein is a sustainable ...heterogeneous‐gold‐catalyzed synthesis of azo arenes. Available nitroarenes are deoxygenated and linked selectively by the formation of NN bonds using molecular H2 without any external additives. As a result of a unique and remarkable synergy between the metal and support, a facile surface‐mediated condensation of nitroso and hydroxylamine intermediates is enabled, and the desired transformation proceeds in a highly selective manner under mild reaction conditions. The protocol tolerates a large variety of functional groups and offers a general and versatile method for the environmentally friendly synthesis of symmetric or asymmetric aromatic azo compounds.
Game of rates: A general approach for the chemoselective hydrogenative coupling of nitroarenes to give the corresponding azo compounds, using a heterogeneous gold catalyst, has been developed. As a result of the remarkable synergy between the metal and support, a facile condensation of transient nitroso and hydroxylamine intermediates proceeds. The desired transformation is highly selective under mild reaction conditions.
Developing new efficient catalytic systems to convert abundant and renewable feedstocks into valuable products in a compact, flexible, and target‐specific manner is of high importance in modern ...synthetic chemistry. Here, we describe a versatile set of mild catalytic conditions utilizing a single gold‐based solid catalyst that enables the direct and additive‐free preparation of four distinct and important amine derivatives (amines, formamides, benzimidazoles, and dimethlyated amines) from readily available formic acid (FA) and nitro starting materials with high level of chemoselectivity. By controlling the stoichiometry of the employed FA, which has attracted considerable interest in the area of sustainable chemistry because of its potential as an entirely renewable hydrogen carrier and as a versatile C1 source, a facile atom‐ and step‐efficient transformation of nitro compounds can be realized in a modular fashion.
Renewable formic acid as a flexible feedstock: A versatile heterogeneous gold‐based catalytic system has been developed for the controlled, flexible, and target‐specific reductive transformation of nitro compounds using stoichiometric equivalents of formic acid as a key starting material under mild and convenient conditions. The overall operational simplicity, high chemoselectivity, functional‐group tolerance, and reusability of the catalyst make this approach an attractive and reliable tool for organic and process chemists.
Formic acid (FA) has tremendous potential as a safe and convenient source of hydrogen for sustainable chemical synthesis and renewable energy storage, but controlled and efficient dehydrogenation of ...FA by a robust solid catalyst under ambient conditions constitutes a major challenge. Here, we report that a previously unappreciated combination of subnanometric gold and an acid-tolerant oxide support facilitates the liberation of CO-free H2 from FA. Applying an ultradispersed gold catalyst comprising TEM-invisible gold subnanoclusters deposited on zirconia to a FA-amine mixture affords turnover frequencies (TOFs) up to 1590 per hour and a turnover number of more than 118 400 at 50 °C. The reaction was accelerated at higher temperatures, but even at room temperature, a significant H2 evolution (TOFs up to 252 h–1 after 20 min) can still be obtained. Preliminary mechanistic studies suggest that the reaction is unimolecular in nature and proceeds via a unique amine-assisted formate decomposition mechanism on Au–ZrO2 interface.
The pursuit of modern sustainable chemistry has stimulated the development of innovative catalytic processes that enable chemical transformations to be performed under mild and clean conditions with ...high efficiency. Herein, we report that gold nanoparticles supported on TiO2 catalyze the chemoselective hydrogenation of functionalized quinolines with H2 under mild reaction conditions. Our results point toward an unexpected role for quinolines in gold-mediated hydrogenation reactions, namely that of promoter; this is in stark contrast to what prevails in the traditional noble metal Pd-, Pt-, and Ru-based catalyst systems, in which quinolines and their derivatives typically act as poisons. As a result of the remarkable promotional effect of quinoline molecules to H2 activation over supported gold, the transformation can proceed smoothly under very mild conditions (even at temperatures as low as 25 °C). Of practical significance is that various synthetically useful functional groups including halogens, ketone, and olefin remain intact during the hydrogenation of quinolines. Moreover, the protocol also shows promise for the regiospecific hydrogenation of the heterocyclic ring of a variety of other biologically important heteroaromatic nitrogen compounds, such as isoquinoline, acridine, and 7,8-benzoquinoline, in a facile manner. Apart from its importance in catalytic hydrogenation, we believe that this intriguing self-promoted effect by reactant molecules may have fundamental implications for the broad field of gold catalysis and form the basis for development of new catalytic procedures for other key transformations.
A golden opportunity: A highly robust catalyst system consisting of gold nanoparticles supported on acid‐tolerant ZrO2 promoted the conversion of biomass‐derived levulinic acid (1) and formic acid ...(2) into γ‐valerolactone without the use of an external H2 supply (see scheme, red). The Au/ZrO2 catalyst was also used for the direct one‐pot synthesis of highly valuable pyrrolidone derivatives from 1, 2, and primary amines (see scheme, blue).
As the NN bond in N2 is one of the strongest bonds in chemistry, the fixation of N2 to ammonia is a kinetically complex and energetically challenging reaction and, up to now, its synthesis is still ...heavily relying on energy and capital intensive Haber–Bosch process (150–350 atm, 350–550 °C), wherein the input of H2 and energy are largely derived from fossil fuels and thus result in large amount of CO2 emission. In this paper, it is demonstrated that by using Au sub‐nanoclusters (≈0.5 nm ) embedded on TiO2 (Au loading is 1.542 wt%), the electrocatalytic N2 reduction reaction (NRR) is indeed possible at ambient condition. Unexpectedly, NRR with very high and stable production yield (NH3: 21.4 µg h−1 mg−1cat., Faradaic efficiency: 8.11%) and good selectivity is achieved at −0.2 V versus RHE, which is much higher than that of the best results for N2 fixation under ambient conditions, and even comparable to the yield and activation energy under high temperatures and/or pressures. As isolated precious metal active centers dispersed onto oxide supports provide a well‐defined system, the special structure of atomic Au cluster would promote other important reactions besides NRR for water splitting, fuel cells, and other electrochemical devices.
Using Au sub‐nanoclusters anchored on TiO2 substrate as a heterogeneous electrocatalyst, the special Au active sites lead to the effective and stable electrochemical N2 reduction reaction with high NH3 yield (21.4 µg h−1 mg−1cat.) and Faradaic efficiency (8.11%) as well as 100% NH3 selectivity at ambient conditions.
Two birds with one auric stone: The title system acts as a highly efficient heterogeneous catalyst for the one-pot tandem synthesis of imines or oximes from alcohols and the corresponding amines ...under mild conditions (see scheme; HAP= hydroxyapatite).
The Diels–Alder cycloaddition of bio-based 2,5-dimethylfuran (DMF) and ethylene and the subsequent dehydration of the cycloadduct intermediate hold promise to produce renewable p -xylene (PX) from ...biomass feedstocks. Developing reliable and robust catalysts for the efficient transformation of concentrated DMF to PX is highly demanded but challenging. Herein we describe an efficient approach to enable practically viable PX production from concentrated DMF (4 mol L −1 ), employing NbO x dispersed atomically on the interior surface of MCM-type mesoporous silica as a potent catalyst. Benefiting from its unique structural merits that lead to significant lowering of the kinetic barrier for cycloadduct intermediate formation, 8Nb/MCM exhibits excellent activity with 100% conversion and over 96% selectivity and stability (marginal activity loss after 5 cycles of reuse) toward the controlled conversion of DMF and related furanic compounds to the corresponding aromatic products using concentrated feeds. These results have important implications for the advancement of next-generation solid multifunctional catalysts by meticulously tuning the pore structure and precise location of active sites with required characteristics.
