Hydrogenation of CO2 to Formate using a Simple, Recyclable, and Efficient Heterogeneous Catalyst.

Today, one of the most imperative targets to realize the conversions of CO2 in industry is the development of practically viable catalytic systems that demonstrate excellent activity, selectivity, and durability. Herein, a simple heterogeneous Ru(III) catalyst is prepared by immobilizing commercially available RuCl3· xH2O onto a bipyridine-functionalized covalent triazine framework, [bpy-CTF-RuCl3], for the first time. This novel catalyst efficiently hydrogenates CO2 into formate with an unprecedented turnover frequency (38800 h-1) and selectivity. In addition, the catalyst excellently maintains its efficiency over successive runs and produces a maximum final formate concentration of ∼2.1 M in just 2.5 h with a conversion of 12% in regard to CO2 feed. The apparent advantages of air stability, ease of handling, simplicity, the use of a readily available metal precursor, and the outstanding catalytic performance make [bpy-CTF-RuCl3] one of the possible candidates for realizing the large-scale production of formic acid/formate by CO2 hydrogenation.

Structural insights into the efficient CO2-reducing activity of an NAD-dependent formate dehydrogenase from Thiobacillus sp. KNK65MA.

CO2 fixation is thought to be one of the key factors in mitigating global warming. Of the various methods for removing CO2, the NAD-dependent formate dehydrogenase from Candida boidinii (CbFDH) has been widely used in various biological CO2-reduction systems; however, practical applications of CbFDH have often been impeded owing to its low CO2-reducing activity. It has recently been demonstrated that the NAD-dependent formate dehydrogenase from Thiobacillus sp. KNK65MA (TsFDH) has a higher CO2-reducing activity compared with CbFDH. The crystal structure of TsFDH revealed that the biological unit in the asymmetric unit has two conformations, i.e. open (NAD(+)-unbound) and closed (NAD(+)-bound) forms. Three major differences are observed in the crystal structures of TsFDH and CbFDH. Firstly, hole 2 in TsFDH is blocked by helix α20, whereas it is not blocked in CbFDH. Secondly, the sizes of holes 1 and 2 are larger in TsFDH than in CbFDH. Thirdly, Lys287 in TsFDH, which is crucial for the capture of formate and its subsequent delivery to the active site, is an alanine in CbFDH. A computational simulation suggested that the higher CO2-reducing activity of TsFDH is owing to its lower free-energy barrier to CO2 reduction than in CbFDH.

Protocol to operate a large-scale CO2 hydrogenation process for formic acid production.

Formic acid is a viable product of CO2 utilization. Here, we present a protocol for designing and operating a pilot-scale formic acid production plant with a 10 kg/day capacity produced via CO2 hydrogenation. We describe the essential process specifications required for successful operation, including prevention of corrosion and formic acid decomposition. We then detail procedures for steady-state operation of the individual units. This protocol provides the necessary information for further scale-up and commercialization of the CO2 hydrogenation process. For complete details on the use and execution of this protocol, please refer to Kim et al.1.

3-Carbamoyl-1-(2-nitrobenzyl)pyridin-ium bromide.

In the title compound, C(13)H(12)N(3)O(3) (+)·Br(-), the benzene and pyridinium rings form a dihedral angle of 82.0 (1)°. In the crystal, N-H⋯Br and N-H⋯O hydrogen bonds link the components into chains along [001]. In addition, weak C-H⋯O and C-H⋯Br hydrogen bonds are observed.

Stereospecific growth of densely populated rutile mesoporous TiO2 nanoplate films: a facile low temperature chemical synthesis approach.

We report for the first time, using a simple and environmentally benign chemical method, the low temperature synthesis of densely populated upright-standing rutile TiO(2) nanoplate films onto a glass substrate from a mixture of titanium trichloride, hydrogen peroxide and thiourea in triply distilled water. The rutile TiO(2) nanoplate films (the phase is confirmed from x-ray diffraction analysis, selected area electron diffraction, energy-dispersive x-ray analysis, and Raman shift) are 20-35 nm wide and 100-120 nm long. The chemical reaction kinetics for the growth of these upright-standing TiO(2) nanoplate films is also interpreted. Films of TiO(2) nanoplates are optically transparent in the visible region with a sharp absorption edge close to 350 nm, confirming an indirect band gap energy of 3.12 eV. The Brunauer-Emmet-Teller surface area, Barret-Joyner-Halenda pore volume and pore diameter, obtained from N(2) physisorption studies, are 82 m(2) g(-1), 0.0964 cm(3) g(-1) and 3.5 nm, respectively, confirming the mesoporosity of scratched rutile TiO(2) nanoplate powder that would be ideal for the direct fabrication of nanoscaled devices including upcoming dye-sensitized solar cells and gas sensors.

An Efficient and Practical System for the Synthesis of N,N-Dimethylformamide by CO2 Hydrogenation using a Heterogeneous Ru Catalyst: From Batch to Continuous Flow.

In the context of CO2 utilization, a number of CO2 conversion methods have been identified in laboratory-scale research; however, only a very few transformations have been successfully scaled up and implemented industrially. The main bottleneck in realizing industrial application of these CO2 conversions is the lack of industrially viable catalytic systems and the need for practically implementable process developments. In this study, a simple, highly efficient and recyclable ruthenium-grafted bisphosphine-based porous organic polymer (Ru@PP-POP) catalyst has been developed for the hydrogenation of CO2 to N,N-dimethylformamide, which affords a highest ever turnover number of 160 000 and an initial turnover frequency of 29 000 h-1 in a batch process. The catalyst is successfully applied in a trickle-bed reactor and utilized in an industrially feasible continuous-flow process with an excellent durability and productivity of 915 mmol h-1 gRu -1 .

Synergistic effect of nano-Pt and Ni spine for HER in alkaline solution: hydrogen spillover from nano-Pt to Ni spine.

The design of active, stable, and cost-effective electrocatalysts for the H2 evolution reaction (HER) in alkaline conditions is important for electrochemical systems such as the chloro-alkaline process and H2 production. Here we report catalysts comprising Pt on Ni single crystalline spines (Pt/Ni-SP) with high activity and stability for HER in alkaline solution with proposed mechanism. The Pt/Ni-SP catalysts are prepared by dispersing platinum nanoparticles (1.7-3.1 nm) on the single-crystalline spines (Ni-SP) of Ni urchin-like particles. The size and coverage of Pt nanoparticles on Ni-SP are increased with increases in the Pt loading amount. X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy are performed to observe the structure of the Pt/Ni-SP catalyst. The catalysts achieve the mass activity of 1.11 A mg-1(Pt), comparing favorably to Pt/C catalysts with the mass activity of 0.33 A mg-1(Pt) at 0.05 V overpotential. The Tafel slope of the Pt/Ni-SP catalyst is approximately 30 mV dec-1, similar to that of Pt, while Pt/Ni-SP is very stable in alkaline solution, like Ni. The synergistic effect of Pt/Ni-SP is ascribed to H spillover from Pt to Ni.

Preparation of mesostructured barium sulfate with high surface area by dispersion method and its characterization.

The spherical and cubic mesoporous BaSO(4) particles with high surface area were successfully produced via one-step process through precipitation reaction in aqueous solution of Ba(OH)(2) and H(2)SO(4) with ethylene glycol (n-HOCH(2)CH(2)OH) as a modifying agent. The BaSO(4) nanomaterial revealed that the high surface area and the mesoporous was stable up to 400 degrees C. Agglomerate mesoporous barium sulfate nanomaterials were obtained by the reaction of Ba(2+) and SO(2-)(4) with ethylene glycol aqueous solution. The ethylene glycol was used to control the BaSO(4) particle size and to modify the surface property of the particles produced from the precipitation. The dried and calcined mesoporous BaSO(4) nanomaterials were characterized by X-ray diffraction (XRD), BET surface area and N(2) adsorption-desorption isotherm, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared resonance (FTIR) and thermogravimetric analysis (TGA). The as-prepared mesoporous dried BaSO(4) possesses a high BET surface area of 91.56 m(2) g(-1), pore volume of 0.188 cm(3) g(-1) (P/P(0)=0.9849) and pore size of 8.22 nm. The SEM indicates that the morphology of BaSO(4) nanomaterial shows shell like particles up to 400 degrees C, after that there is drastically change in the material due to agglomeration. Synthesis of mesoporous BaSO(4) nanomaterial is of significant importance for both sulphuric acid decomposition and oxidation of methane to methanol.

A Highly Efficient Heterogenized Iridium Complex for the Catalytic Hydrogenation of Carbon Dioxide to Formate.

A heterogenized catalyst on a highly porous covalent triazine framework was synthesized and characterized to have a coordination environment similar to that of its homogeneous counterpart. The catalyst efficiently converted CO2 into formate through hydrogenation with a turnover number of 5000 after 2 h and an initial turnover frequency of up to 5300 h(-1) ; both of these values are the highest reported to date for a heterogeneous catalyst, which makes it attractive toward industrial application. Furthermore, the synthesized catalyst was found to be stable in air and was recycled by simple filtration without significant loss of catalytic activity.

Graphene-NiO nanohybrid prepared by dry plasma reduction as a low-cost counter electrode material for dye-sensitized solar cells.

NiO nanoparticles (NPs) were hybridized on the surface of reduced graphene oxide (RGO) by dry plasma reduction (DPR) at atmospheric pressure without any toxic chemicals and at a low temperature. NiO-NPs of 0.5-3 nm size, with a typical size of 1.5 nm, were uniformly hybridized on the surface of RGO. An XPS analysis and the Raman spectra also revealed the repair of some structural damage on the basal plane of the graphene. The material when applied to the counter electrode (CE) of dye-sensitized solar cells (DSCs) exhibited a power conversion efficiency of 7.42% (± 0.10%), which is comparable to a conventional Pt-sputtered CE (8.18% (± 0.08%)). This material outperformed CEs produced using NiO-NPs (1.53% (± 0.15%)), GO (4.48% (± 0.12%)) and RGO (5.18% (± 0.11)) due to its high electrochemical catalytic activity and high conductivity. The charge transfer resistance for NiO-NP-RGO was as low as 1.93 Ω cm(2), while those of a NiO-NP-immobilized electrode and a GO-coated electrode were 44.39 Ω cm(2) and 12.19 Ω cm(2), respectively, due to a synergistic effect.

Water is a key factor to alter the structure and electrochemical properties of carboxylate-bridged dimanganese(II) complexes.

The synthesis and physical properties of dimanganese(II) compounds with varying numbers of water ligands housed in the four bulky carboxylate motifs, including the first complex with a parallelogram core {Mn2(µ-OH2)2(µ-O2CR)}(3+) unit, are described. The isolation of these complexes revealed how water could alter the structural and electrochemical properties of similar carboxylate-bridged dimanganese(II) cores that may occur in a variety of active sites of Mn-containing metalloenzymes. These studies support the notion that water molecules in coordination spheres of active sites of metalloproteins are not a simple spectator medium but the modulation factor of structures and functions.

Efficient CO2-reducing activity of NAD-dependent formate dehydrogenase from Thiobacillus sp. KNK65MA for formate production from CO2 gas.

NAD-dependent formate dehydrogenase (FDH) from Candida boidinii (CbFDH) has been widely used in various CO2-reduction systems but its practical applications are often impeded due to low CO2-reducing activity. In this study, we demonstrated superior CO2-reducing properties of FDH from Thiobacillus sp. KNK65MA (TsFDH) for production of formate from CO2 gas. To discover more efficient CO2-reducing FDHs than a reference enzyme, i.e. CbFDH, five FDHs were selected with biochemical properties and then, their CO2-reducing activities were evaluated. All FDHs including CbFDH showed better CO2-reducing activities at acidic pHs than at neutral pHs and four FDHs were more active than CbFDH in the CO2 reduction reaction. In particular, the FDH from Thiobacillus sp. KNK65MA (TsFDH) exhibited the highest CO2-reducing activity and had a dramatic preference for the reduction reaction, i.e., a 84.2-fold higher ratio of CO2 reduction to formate oxidation in catalytic efficiency (kcat/KB) compared to CbFDH. Formate was produced from CO2 gas using TsFDH and CbFDH, and TsFDH showed a 5.8-fold higher formate production rate than CbFDH. A sequence and structural comparison showed that FDHs with relatively high CO2-reducing activities had elongated N- and C-terminal loops. The experimental results demonstrate that TsFDH can be an alternative to CbFDH as a biocatalyst in CO2 reduction systems.