Efficient homogeneous catalysis in the reduction of CO2 to CO

The well-defined copper(I) boryl complex [(IPr)Cu(Bpin)] [where IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, and pin = pinacolate: 2,3-dimethyl-2,3-butanediolate] deoxygenates CO2 rapidly and quantitatively, affording CO and the borate complex [(IPr)Cu(OBpin)]. The boryl may be regenerated by treatment with the diboron compound pinB-Bpin, giving the stable byproduct pinB-O-Bpin. The use of a copper(I) alkoxide precatalyst and stoichiometric diboron reagent results in catalytic reduction of CO2, with high turnover numbers (1000 per Cu) and frequencies (100 per Cu in 1 h) depending on supporting ligand and reaction conditions.     

Photothermal catalysis for CO2 conversion

The conversion of carbon dioxide into useful fuels or chemical feedstocks is of great importance for achieving carbon emission peak and carbon neutrality. The harvesting and conversion of solar energy will provide a sustainable and environmentally friendly energy source for human production and living. Very recently, photothermal catalysis has been proved to exhibit great advantages in reducing the reaction temperature, promoting the catalytic activity, and manipulating the reaction pathway in comparison with traditional thermal catalysis. In this review, we firstly introduced the fundamental mechanisms and categories of photothermal catalysis to understand the synergy or the difference between photochemical and thermochemical reaction pathways. Subsequently, the criteria and strategies for photothermal catalyst design are discussed in order to inspire the development of high-efficiency photothermal catalytic route by achieving intense absorption of broadband solar energy spectrum and high conversion capability of solar-to-heat. Recent progress in CO₂ reduction achieved by photothermal catalysis was summarized in terms of production types. In the end, the future challenges and perspectives of photothermal catalytic CO₂ reduction are presented. We hope that this review will not only deepen the understanding of photothermal catalysis, but also inspire the design, preparation and application of high-performance photothermal catalysts, aiming at alleviating non-renewable fossil energy consumption and carbon emissions for early carbon emission peak and carbon neutrality.     

Engineering of chiral nanomaterials for biomimetic catalysis

Chiral nanomaterial-based biomimetic catalysts can trigger a similar biological effect to natural catalysts and exhibit high performance in biological applications. Especially, their active center similarity and substrate selectivity promoted their superior biocatalytic activity. Here, modification of critical elements, such as size, morphology, nanocrystal facets, chiral surface and active sites, for controlling the catalytic efficiency of individual chiral nanoparticles (NPs) and chiral nanoassemblies has been demonstrated, which had a synergistic effect on overcoming the defects of pre-existing nanocatalysts. Noticeably, application of external forces (light or magnetism) has resulted in obvious enhancement in biocatalytic efficiency. Chiral nanomaterials served as preferable biomimetic nanocatalysts due to their special structural configuration and chemical constitution advantages. Furthermore, the current challenges and future research directions of the preparation of high-performance bioinspired chiral nanomaterials for biological applications are discussed.

Chiral nanomaterial-based biomimetic catalysts can trigger a similar biological effect to natural catalysts and exhibit high performance in biological applications.     

Effects of gamma-irradiation on CO2 fixation and

To investigate the possibility of ¹⁴CO₂ fixation using microorganisms in a high-dose area, the photosynthetic activity (specific production rate: SPR) and cellular proliferation (colony forming unit: CFU) of Euglena gracilis Z irradiated with gamma-rays at a dose of 0 to 500 Gy were determined. The dose responses of SPR and CFU suggested that it was possible to operate a CO₂ fixation system of Euglena up to 100 Gy. Even at a dose of 500 Gy, about half of the photosynthetic activity under non-irradiated condition was considered possible.     

Cascade catalysis for the homogeneous hydrogenation of CO2 to methanol

This communication demonstrates the homogeneous hydrogenation of CO(2) to CH(3)OH via cascade catalysis. Three different homogeneous catalysts, (PMe(3))(4)Ru(Cl)(OAc), Sc(OTf)(3), and (PNN)Ru(CO)(H), operate in sequence to promote this transformation.     

Elucidating the protonation site of vanadium peroxide complexes and the implications for biomimetic catalysis

Coordination complexes of vanadium(5+) played a key role in understanding the structure and mechanism of vanadium-dependent haloperoxidases, particularly the effects of protonation on peroxide coordination to dioxovanadium(5+) species, and in the activation of the peroxo-oxovanadium(5+) complex for substrate oxidation. There has been no spectroscopic evidence that could test the presence of a hydroxo intermediate in a catalytically active oxovanadium(5+) complex. Herein we report the use of the pre-edge transition in X-ray absorption spectroscopy as a spectroscopic signature for V=O bonding. Displacement of oxo donors with hydrogen peroxide or chloride donors dramatically decreases the pre-edge intensity, confirming that the source of the intense pre-edge feature is closely related to the -bonding associated with the V=O. Protonation of a catalytically active tripodal amine oxovanadium(5+) complex has no affect on the pre-edge intensity and, therefore, rules out the possibility of a hydroxo intermediate in the catalytic cycle.     

Recent advances on gas-phase CO2 conversion: Catalysis design and chemical processes to close the carbon cycle

Chemical CO₂ recycling in the gas phase constitutes a straightforward approach for effective CO₂ conversion to added-value products like syngas or synthetic methane. In this scenario, some traditional processes such as the dry and bi-reforming of methane, the CO₂ methanation and the reverse water-gas shift have gained a renewed interest from the CO₂ utilisation perspective. Indeed, these reactions represent flexible routes to upgrade CO₂ and their application at an industrial scale could substantially reduce CO₂ emissions. The bottleneck for the implementation of these processes at the commercial level is the development of highly active and robust heterogeneous catalysts able to overcome CO₂ activation and deliver sufficient amounts of the upgrading products (i.e. syngas or synthetic natural gas) at the desired operating conditions. This review paper gathers the most recent advances in the design of new catalytic formulations for chemical CO₂ recycling in the gas phase and constitutes an overview for experts and newcomers in the field to get fundamental insights into this emerging branch of low-carbon technologies.     

Catalysts design for CO2 electroreduction

To create a harmonious society and mitigate fossil economy,efficient CO₂reducing is a critical step and is urgently needed.CO₂electroreduction (ECO₂RR) technology,which converts greenhouse CO₂to chemical feedstocks and liquid fuels with renewable electricity,is a promising answer to Carbon Neutrality and Paris Agreement[1].Despite the great potential of CO₂electroreduction for energy and environment issues,it is still challenging of this technology.     

Emerging material engineering strategies for amplifying photothermal heterogeneous CO2 catalysis

Closing the carbon loop,through CO2 capture and utilization,is a promising route to mitigate climate change.Solar energy is a sustainable energy source which ca...     

Influence of the nature of the modifying cation on the activity and selectivity of CO/SiO2 catalysis of hydrocarbon synthesis from CO and H2

The catalytic properties of Co/SiO₂ catalysis, modified with cations (L) of various chemical types, were investigated in the synthesis of higher hydrocarbons from synthesis gas. A number of changes ascertained in the specific catalytic activity and selectivity, depending on the nature of L, were interpreted on the basis of the previously substantiated mechanism of hydrogenation of CO on transition metals.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 3, pp. 197–201, May-June, 1992.     

Bifunctional catalysis of Mo/HZSM-5 in the dehydroaromatization of methane with CO/CO2 to benzene and naphthalene

The catalytic dehydrocondensation of methane to aromatics such as benzene and naphthalene was studied on the Mo carbide catalysts supported on micro- and mesoporous materials such as HZSM-5 (0.6 nm) and FSM-16 (2.7 nm). The Mo catalysts supported on H-ZSM-5 having appropriate micropores (0.6 nm size) and Si/Al ratios (20-70) exhibit higher yields (90-150 nmol/g-cat/s) and selectivities (higher than 74% on the carbon basis) in methane conversion to aromatic products such as benzene and naphthalene at 973 K and 1 atm, although they are drastically deactivated because of substantial coke formation. It was demonstrated that the CO/CO₂ addition to methane effectively improves the catalyst performance by keeping a higher methane conversion and selectivities of benzene formation in the prolonged time-on-stream. The oxygen derived from CO and CO₂ dissociation suppresses polycondensation of aromatic products and coke formation in the course of methane conversion. XAFS and TG/DTA/mass-spectrometric studies reveal that the zeolite-supported Mo oxide is endothermally converted under the action of methane around 955 K to nanosized particles of molybdenum carbide (Mo₂C) (Mo-C, coordination number = 1,R- 2.09 å; Mo-Mo, coordination number = 2.3–3.5;R = 2.98 å). The SEM pictures showed that the nanostructured Mo carbide particles are highly dispersed on and inside the HZSM-5 crystals. On the other hand, it was demonstrated by IR measurements of pyridine adsorption that the Mo/HZSM-5 catalysts having the optimum SiO₂/Al₂O₃ ratios around 40 show the maximum Brönsted acidity among the catalysts with the SiO₂/Al₂O₃ ratios of 20–1900. There is a close correlation between the activity of benzene formation in the methane aromatization and the Brönsted acidity of HZSM-5 due to the bifunctional catalysis.     

Modular design in natural and biomimetic soft materials

Under eons of evolutionary and environmental pressure, biological systems have developed strong and lightweight peptide-based polymeric materials by using the 20 naturally occurring amino acids as principal monomeric units. These materials outperform their man-made counterparts in the following ways: 1) multifunctionality/tunability, 2) adaptability/stimuli-responsiveness, 3) synthesis and processing under ambient and aqueous conditions, and 4) recyclability and biodegradability. The universal design strategy that affords these advanced properties involves "bottom-up" synthesis and modular, hierarchical organization both within and across multiple length-scales. The field of "biomimicry"-elucidating and co-opting nature's basic material design principles and molecular building blocks-is rapidly evolving. This Review describes what has been discovered about the structure and molecular mechanisms of natural polymeric materials, as well as the progress towards synthetic "mimics" of these remarkable systems.     

Polymeric frustrated Lewis pairs in CO2/cyclic ether coupling catalysis

Frustrated Lewis pairs (FLPs) are now ubiquitous as metal-free catalysts in an array of different chemical transformations. In this paper we show that this reactivity can be transferred to a polymeric system, offering advantageous opportunities at the interface between catalysis and stimuli-responsive materials. Formation of cyclic carbonates from cyclic ethers using CO₂ as a C₁ feedstock continues to be dominated by metal-based systems. When paired with a suitable nucleophile, discrete aryl or alkyl boranes have shown significant promise as metal-free Lewis acidic alternatives, although catalyst reuse remains illusive. Herein, we leverage the reactivity of FLPs in a polymeric system to promote CO₂/cyclic ether coupling catalysis that can be tuned for the desired epoxide or oxetane substrate. Moreover, these macromolecular FLPs can be reused across multiple reaction cycles, further increasing their appeal over analogous small molecule systems.

Polymeric frustrated Lewis pairs catalyse the coupling of epoxides and oxetanes with CO₂ with high selectivity under mild CO₂ pressures across multiple reaction cycles.     

Electron-withdrawing functional ligand promotes CO2 reduction catalysis in single atom catalyst

Science China Chemistry - Electrochemical carbon dioxide reduction reaction (CO2RR) powered by renewable electricity offers an attractive approach to reduce carbon emission and at the same time...     

Unified synthesis of eudesmanolides,combining biomimetic strategies with homogeneous catalysis and free-radical chemistry

[reaction: see text] A general procedure for the synthesis of both 12,6- and 12,8-eudesmanolides has been developed. The key step is the titanocene-catalyzed radical cyclization of accessible epoxygermacrolides. The novel reagent 2,4,6-trimethyl-1-trimethylsilylpyridinium chloride, both compatible with oxiranes and capable of regenerating Cp(2)TiCl(2) from Cp(2)Ti(Cl)H and Cp(2)Ti(Cl)OAc, played an important role in the catalytic cycle leading to exocyclic alkenes.     

Mechanism of atmospheric CO2 fixation in the cavities of a dinuclear cryptate

Using density functional theory (DFT) methods, we have investigated two possible mechanisms for atmospheric CO(2) fixation in the cavity of the dinuclear zinc(II) octa-azacryptate, and the subsequent reaction with methanol whereby this latter reaction transforms the (essentially) chemically inert CO(2) into useful products. The first mechanism (I) was proposed by Chen et al. [Chem.-Asian J. 2007, 2, 710], and involves the attachment of one CO(2) molecule onto the hydroxyl-cryptate form, resulting in the formation of a bicarbonate-cryptate species and subsequent reaction with one methanol molecule. In addition, we suggest another mechanism that is initiated via the attachment of a methanol molecule onto one of the Zn-centers, yielding a methoxy-cryptate species. The product is used to activate a CO(2) molecule and generate a methoxycarbonate-cryptate. The energy profiles of both mechanisms were determined, and we conclude that, while both mechanisms are energetically feasible, free energy profiles suggest that the scheme proposed by Chen et al. is most likely.     

Environmentally benign chemical fixation of CO2 catalyzed by the functionalized ion-exchange resins

Basic ion-exchange resins, one kind of polystyryl-supported tertiary amine, were demonstrated to be highly efficient and recyclable catalysts for the fixation of carbon dioxide with aziridines under mild conditions, leading to the formation of 5-aryl-2-oxazolidinone with excellent regio-selectivities. Notably, neither solvents nor any additives were required, and the catalyst could be recovered by simple filtration and directly reused at least five times without significant loss of catalytic activity and selectivity. The present protocol has been applied to reactions of epoxides/propargyl amines with CO₂/CS₂. This solvent-free process thus represents environmentally friendly catalytic conversion of CO₂ into value-added chemicals and may have potential in various continuous flow reactors in industry.     

Cobalt-based catalytic system for the chemical fixation of CO2 under solvent-free conditions

We have described a novel and efficient method for synthesizing cyclic carbonates with ‘Co (NO₃)₂ ^. 6H₂O/ L6 ’-catalyzed coupling of epoxides and CO₂ under solvent-free conditions. We proposed a possible reaction mechanism based on some control experiments. Phenylpropiolic acid could be provided by using the same method.     

Polystyrene-bound diethanolamine based ionic liquids for chemical fixation of CO2

Polystyrene-bound diethanolamine based ionic liquids (PS-DHEEAB and PS-THEAB) were synthesized and applied for the chemical fixation of CO₂ into cyclic carbonates without any additional co-catalyst and solvent. The effect of the catalysts with different number of hydroxyl group in the cation of the IL on the reaction was systematically investigated. Highest activity and selectivity were achieved in the presence of polystyrene supported diethanolamine ethyl bromide (PS-DHEEAB) in comparison with other catalysts employed. The catalyst was tough in stability and also found to be extended to a variety of terminal epoxides and aziridines. The relationship between high catalytic reactivity and the –OH functional groups was proposed.