Carbon Dioxide as a Raw Material: The Synthesis of Formic Acid and Its Derivatives from CO2

The use of carbon dioxide as a raw material for chemical syntheses is an ecologically and economically valuable extension to the carbon sources used at the present time. In order to convert the thermodynamically stable and comparatively unreactive CO₂ molecule into the desired product in an efficient manner, suitable reaction conditions and activation mechanisms must be found. The catalytic reduction of CO₂ to formic acid and its derivatives has been intensively studied in recent years. A number of new approaches to the synthesis of formic acid from CO₂ have reached such a state of knowledge that continuing development may well lead to industrial-scale operation in the near future. This can to a large extent be attributed to the fruitful interaction between investigative work into reaction mechanisms and the development of new catalytic systems.     

Zeolite-Encaged Pd–Mn Nanocatalysts for CO2 Hydrogenation and Formic Acid Dehydrogenation

A CO₂-mediated hydrogen storage energy cycle is a promising way to implement a hydrogen economy, but the exploration of efficient catalysts to achieve this process remains challenging. Herein, sub-nanometer Pd–Mn clusters were encaged within silicalite-1 (S-1) zeolites by a ligand-protected method under direct hydrothermal conditions. The obtained zeolite-encaged metallic nanocatalysts exhibited extraordinary catalytic activity and durability in both CO₂ hydrogenation into formate and formic acid (FA) dehydrogenation back to CO₂ and hydrogen. Thanks to the formation of ultrasmall metal clusters and the synergic effect of bimetallic components, the PdMn_0.6@S-1 catalyst afforded a formate generation rate of 2151 mol_formate mol_Pd⁻¹ h⁻¹ at 353 K, and an initial turnover frequency of 6860 mol mol_Pd⁻¹ h⁻¹ for CO-free FA decomposition at 333 K without any additive. Both values represent the top levels among state-of-the-art heterogeneous catalysts under similar conditions. This work demonstrates that zeolite-encaged metallic catalysts hold great promise to realize CO₂-mediated hydrogen energy cycles in the future that feature fast charge and release kinetics.     

Selective Formic Acid Decomposition for High‐Pressure Hydrogen Generation: A Mechanistic Study

A viable storage system for hydrogen based on selective formic acid decomposition into H₂ and CO₂ has been developed (see scheme). Continuous generation of H₂ of very high purity, over a wide range of pressures and under mild conditions was achieved.

     

Photochemically Engineering the Metal–Semiconductor Interface for Room‐Temperature Transfer Hydrogenation of Nitroarenes with Formic Acid

A mild photochemical approach was applied to construct highly coupled metal–semiconductor dyads, which were found to efficiently facilitate the hydrogenation of nitrobenzene. Aniline was produced in excellent yield (>99 %, TOF: 1183) using formic acid as hydrogen source and water as solvent at room temperature. This general and green catalytic process is applicable to a wide range of nitroarenes without the involvement of high‐pressure gases or sacrificial additives.     

Exploiting the Multidentate Nature of Chiral Disulfonimides in a Multicomponent Reaction for the Asymmetric Synthesis of Pyrrolo[1,2‐a]indoles: A Remarkable Case of Enantioinversion

A new multicomponent coupling reaction for the enantioselective synthesis of pyrrolo[1,2‐a]indoles under the catalysis of a chiral disulfonimide is described. The high specificity of the reaction is a consequence of the multidentate character of the Brønsted acid catalyst. Insights from DFT calculations helped explain the unexpected high enantioselectivity observed with the simplest 3,3′‐unsubstituted binaphthyl catalyst as a result of transition‐state stabilization by a network of cooperative noncovalent interactions. The remarkable enantioinversion resulting from the simple introduction of substituents at 3‐ and 3′‐positions, the first reported example of this phenomenon in the context of binaphthalene‐derived Brønsted acid catalysis, was instead attributed to destabilizing steric interactions.     

Ligand Effect on the Stability of Water-Soluble Iridium Catalysts for High-Pressure Hydrogen Gas Production by Dehydrogenation of Formic Acid

Aiming to develop a highly effective and durable catalyst for high-pressure H₂ production from dehydrogenation of formic acid (DFA), the ligand effect on the catalytic activity and stability of Cp*Ir (Cp*:pentamethylcyclopentadienyl anion) complexes were investigated using 5 different kinds of N,N’-bidentate ligands (bipyridine, biimidazoline, pyridyl-imidazoline, pyridyl-pyrazole and picolinamide). The Ir complex with biimidazoline ligand exhibited the highest catalytic activity, but deactivation occurred readily at high pressure. The pyridine moiety in the ligand can enhance the stability of Ir complex catalysts for the high-pressure reaction. The Ir complex catalyst containing pyridyl-imidazoline ligand showed the high activity and best stability under the high-pressure conditions.     

Efficient Reduction of CO2 into Formic Acid on a Lead or Tin Electrode using an Ionic Liquid Catholyte Mixture

Highly efficient electrochemical reduction of CO₂ into value‐added chemicals using cheap and easily prepared electrodes is environmentally and economically compelling. The first work on the electrocatalytic reduction of CO₂ in ternary electrolytes containing ionic liquid, organic solvent, and H₂O is described. Addition of a small amount of H₂O to an ionic liquid/acetonitrile electrolyte mixture significantly enhanced the efficiency of the electrochemical reduction of CO₂ into formic acid (HCOOH) on a Pb or Sn electrode, and the efficiency was extremely high using an ionic liquid/acetonitrile/H₂O ternary mixture. The partial current density for HCOOH reached 37.6 mA cm^?2 at a Faradaic efficiency of 91.6 %, which is much higher than all values reported to date for this reaction, including those using homogeneous and noble metal electrocatalysts. The reasons for such high efficiency were investigated using controlled experiments.     

A Reusable Co Catalyst for the Selective Hydrogenation of Functionalized Nitroarenes and the Direct Synthesis of Imines and Benzimidazoles from Nitroarenes and Aldehydes

The use of abundantly available transition metals in reactions that have been preferentially mediated by rare noble metals, for example, hydrogenations, is a desirable aim in catalysis and an attractive strategy for element conservation. The observation of novel selectivity patterns with such inexpensive metal catalysts is especially appealing. Herein, we report a novel, robust, and reusable cobalt catalyst that permits the selective hydrogenation of nitroarenes in the presence of highly hydrogenation‐sensitive functional groups, as well as the direct synthesis of imines from nitroarenes and aldehydes or ketones in the presence of such substituents. Furthermore, we introduce the first base‐metal‐mediated direct synthesis of benzimidazoles from nitroarenes and aldehydes. Functional groups that are easy to hydrogenate are again well tolerated.     

An Anthracene-Based Metal-Organic Framework for Selective Photo-Reduction of Carbon Dioxide to Formic Acid Coupled with Water Oxidation

A Zr-based metal-organic framework has been synthesized and employed as a catalyst for photochemical carbon dioxide reduction coupled with water oxidation. The catalyst shows significant carbon dioxide reduction property with concomitant water oxidation. The catalyst has broad visible light as well as UV light absorption property, which is further confirmed from electronic absorption spectroscopy. Formic acid was the only reduced product from carbon dioxide with a turn-over frequency (TOF) of 0.69 h⁻¹ in addition to oxygen, which was produced with a TOF of 0.54 h⁻¹. No external photosensitizer is used and the ligand itself acts as the light harvester. The efficient and selective photochemical carbon dioxide reduction to formic acid with concomitant water oxidation using Zr-based MOF as catalyst is thus demonstrated here.     

甲酸存在下 N-四氢苯并噻唑亚胺希夫碱的化学发光

新合成的N(2-四氢苯并噻唑)-2-羟基苯甲亚胺希夫碱与酸性高锰酸钾反应产生微弱的化学发光,甲酸的存在有显著的增敏作用。报道了其荧光光谱、化学发光光谱、紫外可见吸收光谱和化学发光动力学曲线,并建立了流动注射化学发光测定噻唑类希夫碱的方法。该法线性范围为1.0×10-7～8.0×10-5mol/L,检测限为5.0×10-8mol/L,对1.0×10-6mol/L噻唑类希夫碱11次平行测定的相对标准偏差为1.7％。     

Pd-Catalyzed Reduction of Aldehydes to Alcohols Using Formic Acid as the Hydrogen Donor

Facile and selective reduction of aromatic aldehydes as well as aliphatic aldehydes to alcohols was achieved using formic acid as the hydrogen donor in the presence of a catalytic amount of Pd(OAc)₂ and Cy₃P. It was found that both hydrogen atoms in the formic acid molecule can serve as the hydride source.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

The Role of Co-Adsorbed CO and OH in the Electrooxidation of Formic Acid on Pt(111)

Synergy with potential: Analysis of relevant mechanistic pathways by density functional theory, reveals the synergistic role of co-adsorbed CO and OH in promoting HCOOH electrooxidation on Pt(111). Kinetic models derived from these studies show the atomistic surface phenomena underlying the experimental CV observation in the potential range between 0.0 and 1.2?V.     

Oxidative Conversion of Glucose to Formic Acid as a Renewable Hydrogen Source Using an Abundant Solid Base Catalyst

Formic acid is one of the most desirable liquid hydrogen carriers. The selective production of formic acid from monosaccharides in water under mild reaction conditions using solid catalysts was investigated. Calcium oxide, an abundant solid base catalyst available from seashell or limestone by thermal decomposition, was found to be the most active of the simple oxides tested, with formic acid yields of 50 % and 66 % from glucose and xylose, respectively, in 1.4 % H₂O₂ aqueous solution at 343 K for 30 min. The main reaction pathway is a sequential formation of formic acid from glucose by C−C bond cleavage involving aldehyde groups in the acyclic form. The reaction also involves base-catalyzed aldose-ketose isomerization and retroaldol reaction, resulting in the formation of fructose and trioses including glyceraldehyde and dihydroxyacetone. These intermediates were further decomposed into formic acid or glycolic acid. The catalytic activity remained unchanged for further reuse by a simple post-calcination.     

A General,Activator‐Free Palladium‐Catalyzed Synthesis of Arylacetic and Benzoic Acids from Formic Acid

A new catalyst for the carboxylative synthesis of arylacetic and benzoic acids using formic acid (HCOOH) as the CO surrogate was developed. In an improvement over previous work, CO is generated in situ without the need for any additional activators. Key to success was the use of a specific system consisting of palladium acetate and 1,2‐bis((tert‐butyl(2‐pyridinyl)phosphinyl)methyl)benzene. The generality of this method is demonstrated by the synthesis of more than 30 carboxylic acids, including non‐steroidal anti‐inflammatory drugs (NSAIDs), under mild conditions in good yields.     

泡沫铜负载硫化亚铜电极高效电催化还原二氧化碳制备甲酸

电催化还原二氧化碳制备甲酸是备受关注的热点问题。而电极材料是决定还原效率的重要因素。本文通过电沉积方法在泡沫铜上直接制备纳米结构硫化亚铜薄膜,并采用扫描电镜(SEM)、X射线衍射(XRD)对其结构性能进行了系统研究。以硫化亚铜作为阴极电催化材料、0.5 mol·L^-1 1-丁基-3-甲基咪唑四氟硼酸盐的乙腈溶液为电解液,在该体系中可高效催化转化二氧化碳为甲酸。结果表明,这一电解体系可有效实现电化学反应,甲酸的法拉第效率(FE_HCOOH)可以达到85%,同时甲酸还原电流密度可达到5.3 mA·cm^-2。     

Formic Acid,a Ubiquitous but Overlooked Component of the Early Earth Atmosphere

Terrestrial volcanism has been one of the dominant geological forces shaping our planet since its earliest existence. Its associated phenomena, like atmospheric lightning and hydrothermal activity, provide a rich energy reservoir for chemical syntheses. Based on our laboratory simulations, we propose that on the early Earth volcanic activity inevitably led to a remarkable production of formic acid through various independent reaction channels. Large-scale availability of atmospheric formic acid supports the idea of the high-temperature accumulation of formamide in this primordial environment.