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Electric‐driven conversion of carbon dioxide (CO2) to carbon monoxide (CO) under mild reaction conditions offers a promising approach to mitigate the greenhouse effect and the energy crisis. Surface engineering is believed to be one of the prospective methods for enhancing the electrocatalytic activity of CO2 reduction. Herein, hydroxyl (OH) groups were successfully introduced to cadmium nanosheets to form cadmium and cadmium hydroxide nanocomposites (i. e. Cd/Cd(OH)2 nanosheets) via a facile two‐step method. The as‐prepared Cd/Cd(OH)2/CP (CP indicates carbon paper) electrode displays excellent electrocatalytic activity for CO2 reduction to produce CO. The Faradaic efficiency of CO reaches 98.3 % and the current density achieves 23.8 mA cm−2 at −2.0 V vs. Ag/Ag+ in a CO2‐saturated 30 wt% 1‐butyl‐3‐methylimidazole hexafluorophosphate ([Bmim]PF6)‐65 wt% acetonitrile (CH3CN)‐5 wt% water (H2O) electrolyte. And the CO partial current density can reach up to 71.6 mA cm−2 with the CO Faradaic efficiency of more than 85 % at −2.3 V vs. Ag/Ag+, which stands out against Cd/CP, Cd(OH)2/CP, and Cd/CdO/CP electrodes. The excellent electrocatalytic performance of the Cd/Cd(OH)2/CP electrode can be attributed to its unique structural properties, suitable OH groups, perfect interaction with electrolyte, abundant active sites and fast electron transfer rate. [ABSTRACT FROM AUTHOR]

A novel electrochemically assisted cycloaddition process is proposed, in which highly efficient coupling of CO2 with styrene oxide (SO) can be achieved to form styrene carbonate (SC) as a high‐value‐added product. A series of Cu catalysts with different morphologies and chemical states were fabricated on carbon paper (CP) by using in‐situ electrodeposition, and the sample with nano‐dendrimer structure was found to exhibit a relatively high activity of 74.8 % SC yield with 92.7 % SO conversion under gentle reaction conditions, thus showing its potential for practical applications. The relatively high electrochemically active surface area and charge transfer ability of dendrimer‐like Cu benefited the electrochemical reaction. In particular, the Cu2+ species that were formed in situ during the reaction played a vital role in enhancing the activity and selectivity of the proposed Cu/CP hybrid catalyst. Cu2+ atoms served as active sites that can not only electrochemically activate CO2 but also facilitate the ring opening of SO. Mechanistic analysis suggested that the reaction followed electrochemical and liquid‐phase heterogeneous paths, which provide a new green and sustainable route for efficient utilization of CO2 resources for fine chemical electrosynthesis. [ABSTRACT FROM AUTHOR]

Gallium hydrides stabilised by primary and secondary amines are scarce due to their propensity to eliminate dihydrogen. Consequently, their reactivity has received limited attention. The synthesis of two novel gallium hydride complexes HGa(THF)[ON(H)O] and H2Ga[μ2‐ON(H)O]Ga[ON(H)O] ([ON(H)O]2−=N,N‐bis(3,5‐di‐tert‐butyl‐2‐phenoxy)amine) is described and their reactivity towards aldehydes and ketones is explored. These reactions afford alkoxide‐bridged dimers through 1,2‐hydrogallation reactions. The gallium hydrides can be regenerated through Ga−O/B−H metathesis from the reaction of such dimers with pinacol borane (HBpin) or 9‐borabicyclo[3.3.1]nonane (9‐BBN). These observations allowed us to target the catalytic reduction of carbonyl substrates (aldehydes, ketones and carbon dioxide) with low catalyst loadings at room temperature. [ABSTRACT FROM AUTHOR]

Evidence is provided that in a gas‐solid photocatalytic reaction the removal of photogenerated holes from a titania (TiO2) photocatalyst is always detrimental for photocatalytic CO2 reduction. The coupling of the reaction to a sacrificial oxidation reaction hinders or entirely prohibits the formation of CH4 as a reduction product. This agrees with earlier work in which the detrimental effect of oxygen‐evolving cocatalysts was demonstrated. Photocatalytic alcohol oxidation or even overall water splitting proceeds in these reaction systems, but carbon‐containing products from CO2 reduction are no longer observed. H2 addition is also detrimental, either because it scavenges holes or because it is not an efficient proton donor on TiO2. The results are discussed in light of previously suggested reaction mechanisms for photocatalytic CO2 reduction. The formation of CH4 from CO2 is likely not a linear sequence of reduction steps but includes oxidative elementary steps. Furthermore, new hypotheses on the origin of the required protons are suggested. [ABSTRACT FROM AUTHOR]

Pincer ligated coordination complexes of base metals have shown remarkable catalytic activity for hydrogenation/dehydrogenation of CO2. The recently reported MeN[CH2CH2(iPr2)]2Co(I)PNP‐pincer complex was shown to exhibit substantially higher catalytic activity in comparison to the corresponding catalyst, HN[CH2CH2(iPr2)]2Co(I)PNP, bearing a secondary nitrogen center on the pincer ligand. Here, we computationally investigate the mechanisms for hydrogenation of CO2 to formate catalyzed by these two Co‐PNP complexes to explain how such a small structural difference could have a sizable impact on their catalytic activity. Plausible hydrogenation routes were examined in details and our findings provide solid support for the experimental observations. Our results reveal that such trends in catalytic activity could be explained from the lower activation barrier for the hydride transfer step upon changing the pincer nitrogen center from secondary to tertiary. [ABSTRACT FROM AUTHOR]

The photocatalytic reduction of CO2 into fuels offers the prospect for creating a new CO2 economy. Harnessing visible light‐driven CO2‐to‐CO reduction mediated by the long‐lived triplet excited state of rhenium(I) tricarbonyl complexes is a challenging approach. We here develop a series of new mononuclear rhenium(I) tricarbonyl complexes (Re‐1−Re‐4) based on the imidazole‐pyridine skeleton for photo‐driven CO2 reduction. These catalysts are featured by combining pyridyl‐imidazole with the aromatic ring and different pendant organic groups onto the N1 position of 1,3‐imidazole unit, which display phosphorescence under Ar‐saturated solution even at ambient conditions. By contrast, {Re[9‐(pyren‐1‐yl)‐10‐(pyridin‐2‐yl)‐9H‐pyreno[4,5‐d]imidazole)](CO)3Cl} (Re‐4) by introducing pyrene ring at the N1 position of pyrene‐fused imidazole unit exhibits superior catalytic performance with a higher turnover number for CO (TONCO=124) and >99.9 % selectivity, primarily ascribed to the strong visible light‐harvesting ability, long‐lived triplet lifetimes (164.2 μs) and large reductive quenching constant. Moreover, the rhenium(I) tricarbonyl complexes derived from π‐extended pyrene chromophore exhibit a long lifetime corresponding to its ligand‐localized triplet state (3IL) evidenced from spectroscopic investigations and DFT calculations. [ABSTRACT FROM AUTHOR]

The rapidly rising level of carbon dioxide in the atmosphere resulting from human activity is one of the greatest environmental problems facing our civilization today. Most technologies are not yet sufficiently developed to move existing infrastructure to cleaner alternatives. Therefore, techniques for capturing carbon dioxide from emission sources may play a key role at the moment. The structure of the UiO‐66 material not only meets the requirement of high stability in contact with water vapor but through the water pre‐adsorbed in the pores, the selectivity of carbon dioxide adsorption is increased. We successfully applied the recently developed methodology for water adsorption modelling. It allowed to elucidate the influence of water on CO2 adsorption and study the mechanism of this effect. We showed that water is adsorbed in octahedral cage and stands for promotor for CO2 adsorption in less favorable space than tetrahedral cages. Water plays a role of a mediator of adsorption, what is a general idea of improving affinity of adsorbate. On the basis of pre‐adsorption of methanol as another polar solvent, we have shown that the adsorption sites play a key role here, and not, as previously thought, only the interaction between the solvent and quadrupole carbon dioxide. Overall, we explained the mechanism of increased CO2 adsorption in the presence of water and methanol, as polar solvents, in the UiO‐66 pores for a potential post‐combustion carbon dioxide capture application. [ABSTRACT FROM AUTHOR]

The heterolytic decomposition of tert‐butyl peroxyformate to tert‐butanol and carbon dioxide, catalyzed by pyridine, is a long‐known example of a reaction whose kinetics are strongly affected by solvent polarity. From DFT and ab initio methods together with the SMD implicit solvation model, an extension on the formerly accepted mechanism is proposed. This novel proposal involves the formation of a carbonic acid ester intermediate and its further decomposition, through an unreported pyridine‐mediated stepwise route. Computed barriers for this mechanism at DLPNO/CCSD(T)‐def2‐TZVP are in excellent agreement with experimental kinetic data across different solvents. Furthermore, the strong relationships between activation energies, geometric parameters in the transition state and the characteristics of the different solvents are also analyzed in depth. [ABSTRACT FROM AUTHOR]

The reaction of dialane [LAl‐AlL] (1; L=dianion of 1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene, dpp‐bian) with carbon dioxide results in two different products depending on solvent. In toluene at temperatures of about 0 °C, the reaction gives cycloadduct [L(CO2)Al‐Al(O2C)L] (2), whereas in diethyl ether, the reaction affords oxo‐bridged carbamato derivative [L(CO2)(Et2O)Al(μ‐O)AlL] (3). The DFT and QTAIM calculations provide reasonable explanations for the reversible formation of complex 2 in the course of two subsequent (2+4) cycloaddition reactions. Consecutive transition states with low activation barriers were revealed. Also, the DFT study demonstrated a crucial effect of diethyl ether coordination to aluminium on the reaction of dialane 1 with CO2. The optimized structures of key intermediates were obtained for the reactions in the presence of Et2O; calculated thermodynamic parameters unambiguously testify the irreversible formation of the product 3. [ABSTRACT FROM AUTHOR]

Electrocatalysis The Ru complex is set on its path, along which it must cross either a high mountain (EEC pathway) or a smaller hill (ECE pathway) to reach the glittering green palace where it can fulfill its goal of converting CO2 to CO. The sun shines brighter on the ECE path, which is alluring and less energy‐demanding. The complex can tread that path provided that its Ru heart has electrons (e−) pumped in (tBu on terpyridine), and that the CH3CN is easily removed. This is achieved by a CH3 group at the bipyridine, which pushes the bipyridine into the CH3CN with the force of a bull, thereby facilitating CH3CN dissociation from the complex. More information can be found in the Full Paper by S. Ott, S. Maji et al. on page 14870 ff. [ABSTRACT FROM AUTHOR]

The image illustrates the operation mechanism of the photothermal activation of Ru/Au nanoparticles deposited on Siralox. Upon absorption of light by Au nanoparticles, the photon energy is thermalized, leading to the heating of smaller Ru nanoparticles located on the Au surface. This local heating serves to promote the selective methanation of CO2 by H2. For more information, see the Full Paper by H. García et al. on page 18436 ff. [ABSTRACT FROM AUTHOR]

Single nickel atoms are uniformly formed over graphene sheets with the assistance of tris(2‐benzimidazolylmethyl)amine (NTB) ligands. Strong interactions of NTB ligands between graphene oxide (GO) sheets and nickel ions facilitates the homogenous dispersion of nickel atoms over the GO sheets. Homogeneously dispersed Ni(NTB)–GO sheets were then chemically transformed into highly active single‐atom nickel sites that show high faradaic efficiency and selectivity for electrochemical CO2 to CO reduction reaction. For more information, see the Full Paper by K. T. Nam et al. on page 18444 ff. [ABSTRACT FROM AUTHOR]

Porphyrinoids CO2 is a cheap, abundant, and nontoxic C1 source, and the chemical conversion of CO2 into useful organic compounds has become increasingly important. In their Full Paper on page 6556 ff., C. Maeda, J. Hasegawa, T. Ema et al. describe the synthesis of bifunctional metalloporphyrins with quaternary ammonium bromides at the meta, para, or ortho positions of the meso‐phenyl groups and investigated their catalytic activities in the formation of cyclic carbonates from epoxides and CO2 under solvent‐free conditions. [ABSTRACT FROM AUTHOR]

Cyclic organoalane compounds [(ADCAr)AlH2]2 (ADCAr = ArC{(DippN)C}2; Dipp = 2,6‐iPr2C6H3; Ar = Ph or 4‐PhC6H4 (Bp)) based on anionic dicarbene (ADC) frameworks have been reported as crystalline solids. Treatments of Li(ADCAr) with LiAlH4 at room temperature afford [(ADCAr)AlH2]2 with the concomitant release of LiH. Compounds [(ADCAr)AlH2]2 are stable crystalline solids and are freely soluble in common organic solvents. They are annulated tricyclic compounds with an almost planar central C4Al2‐core embedded between two peripheral 1,3‐imidazole (C3N2) rings. At room temperature, [(ADCPh)AlH2]2 readily reacts with CO2 to form two‐ and four‐fold hydroalumination products [(ADCPh)AlH(OCHO)]2 and [(ADCPh)Al(OCHO)2]2, respectively. Further hydroalumination reactivity of [(ADCPh)AlH2]2 has been shown with isocyanate (RNCO) and isothiocyanate (RNCS) species (R=alkyl or aryl group). All compounds have been characterized by NMR spectroscopy, mass spectrometry, and single‐crystal X‐ray diffraction. [ABSTRACT FROM AUTHOR]

Cross‐pinacol coupling of two different carbonyl compounds was achieved through successive one‐electron transfer processes under photocatalytic conditions. In the reaction, an umpoled anionic carbinol synthon was generated in situ to react nucleophilically with a second electrophilic carbonyl compound. It was revealed that a CO2 additive promoted the photocatalytic generation of the carbinol synthon to suppress undesired radical dimerization. A wide variety of aromatic and aliphatic carbonyl substrates underwent the cross‐pinacol coupling to afford the corresponding unsymmetric vicinal 1,2‐diols, in which even a combination of carbonyl reactants with similar structures such as two aldehydes and two ketones were also well tolerated with high cross‐coupling selectivity. [ABSTRACT FROM AUTHOR]

CO2 adsorption and activation on Cu single atom catalysts and Cu nanoclusters supported on the (110) surface of rutile and on the (101) surface of anatase TiO2 have been investigated by means of first principles electronic structure calculations. The role of oxide reduction associated to the presence of oxygen vacancies has been considered. Five main messages emerge from this study. (1) CO2 activation on Cu/TiO2 nanostructures is surface sensitive, as the rutile and anatase surfaces can exhibit different behaviors; (2) the surface morphology is essential since CO2 is activated only when the molecule can simultaneously bind to at least two active sites, such as a Cu atom on one side and an oxide ion on the other site; (3) Cu atoms on TiO2 are in the +I oxidation state and can bind and activate CO2 via charge transfer from the oxide; (4) on supported Cu clusters CO2 activation occurs mostly at the metal/oxide interface; (5) the presence of O vacancy sites facilitates the spontaneous dissociation of CO2 to CO, or increases the electron density of the metal catalyst, two effects that can influence the mechanism of CO2 reduction to methanol or other chemicals. [ABSTRACT FROM AUTHOR]

In recent years terpyridines (tpy) and mesoionic carbenes (MIC) have been widely used in metal complexes. With the right combination with a metal center, both of these ligands are individually known to generate excellent catalysts for CO2 reduction. In this study, we combine the potentials of PFC (PFC=polyfluorocarbon) substituted tpy and MIC ligands within the same platform to obtain a new class of complexes, which we investigated with respect to their structural, electrochemical and UV/Vis/NIR spectroelectrochemical properties. We further show that the resulting metal complexes are potent electrocatalysts for CO2 reduction in which CO is exclusively formed with a faradaic efficiency of 92 %. A preliminary mechanistic study, including the isolation and characterization of a key intermediate is also reported. [ABSTRACT FROM AUTHOR]

The reactivity of carbon dioxide with vanadium(III) aryloxo complexes has been investigated. The formation of either carbon monoxide or incorporation into the ligand system with the ultimate formation of organic ester was observed depending on the overall electron donor ability of the ligand field. DFT calculations were carried out to investigate the proposed mechanism for carbon dioxide coordination and reduction. [ABSTRACT FROM AUTHOR]

A new mechanism is proposed for the Ni-catalyzed carboxylation of organoboronates with CO2. DFT investigations at the PBE0-D3 level have shown that direct CO2 addition to the catalysts [Ni(NHC)(Allyl)Cl] ( 1NHC, NHC=IMe, IPr, SIPr and IPr*) is kinetically disfavored and formation of the Aresta-type intermediate is unlikely to occur. According to the mechanism proposed here, the carboxylation process starts with addition of the borate species to 1NHC, followed by transmetalation, CO2 cycloaddition and carboxylation. The rate-determining step was identified as being the transmetalation process, with computed relative free energy barriers of 34.8, 36.8, and 33.5 kcal mol−1 for 1IPr, 1SIPr and 1IPr*, respectively. [ABSTRACT FROM AUTHOR]

Dye-containing wastewater has caused serious environmental pollution. Herein, rationally designed spherical polyelectrolyte brushes (SPBs) with cationic charges, polystyrene-poly(2-aminoethylmethacrylate hydrochloride) (PS-PAEMH) as the absorbent, and compressed carbon dioxide as the antisolvent are proposed for the separation of the anionic dye eosin Y (EY) from a solution of mixed dyes. The adsorption behavior of EY onto PS-PAEMH was highly dependent on CO2 pressure, contact time, and initial concentration. The maximum adsorption capacity of PS-PAEMH was 335.20 mg g−1. FTIR and UV/Vis measurements proved that the electrostatic interactions between EY and PS-PAEMH played an important role in the absorbance process. The adsorption process fitted the pseudo-second-order kinetic model and Freundlich isotherm model very well. The combined dye and polymer brush could be easily separated through ion exchange by adding an aqueous solution of NaCl. Recovered PS-PAEMH retained a high adsorption capacity even after ten cycles of regeneration. This method provides a simple and effective way to separate ionic materials for environmental engineering. [ABSTRACT FROM AUTHOR]

Chemical activation of CO2is problematic due to its high thermodynamic and kinetic stability. Consequently, the use of CO2 for the efficient construction of CC bonds represents a significant challenge. An efficient domino ruthenium‐catalyzed reverse water‐gas‐shift (RWGS)–hydroformylation–reduction reaction of olefins with CO2 to alcohols is reported. For more details, see the Full Paper by I. Fleischer, M. Beller et al. on page 6888 ff. [ABSTRACT FROM AUTHOR]

The electronic features of gold‐aluminyl complexes have been thoroughly explored. Their similarity with Group 14 dimetallenes and other metal‐aluminyl complexes suggests that their reactivity with small molecules beyond carbon dioxide could be accessed. In this work, the reactivity of the [tBu3PAuAl(NON)] (NON=4,5‐bis(2,6 diisopropylanilido)‐2,7‐ditert‐butyl‐9,9‐dimethylxanthene) complex towards water, ammonia, sulfur dioxide and nitrous oxide is computationally explored. The reaction mechanisms computed for each substrate strongly suggest that all activation processes are in principle experimentally feasible. Electronic structure analysis highlights that, in all cases, the reactivity is driven by the presence of the poorly polarized electron‐sharing gold‐aluminyl bond, which induces a radical‐like reactivity of the complex towards all the substrates. A flat topology of the potential energy surface (PES) has been found for the reaction with N2O, where two almost isoenergetic transition states can be located along the same reaction coordinate with different geometries, suggesting that the N2O binding mode may not be a good indicator of the nature of N2O activation in a cooperative bimetallic reactivity. In addition, the catalytic potentialities of these complexes have been explored in the framework of nitrous oxide reduction. The study reveals that the [tBu3PAuAl(NON)] complex might be an efficient catalyst towards oxidation of phosphines (and boranes) via N2O reduction. These findings underline recurring trends in the novel chemistry of gold‐aluminyl complexes and call for experimental feedbacks. [ABSTRACT FROM AUTHOR]

The reactions of a terminal aluminium imide with a range of oxygen‐containing substrates have been probed with a view to developing its use as a novel main group transfer agent for the [NR]2− fragment. We demonstrate transfer of the imide moiety to [N2], [CO] and [Ph(H)C] units driven thermodynamically by Al−O bond formation. N2O reacts rapidly to generate the organoazide DippN3 (Dipp=2,6‐iPr2C6H3), while CO2 (under dilute reaction conditions) yields the corresponding isocyanate, DippNCO. Mechanistic studies, using both experimental and quantum chemical techniques, identify a carbamate complex K2[(NON)Al‐{κ2−(N,O)−N(Dipp)CO2}]2 (formed via [2+2] cycloaddition) as an intermediate in the formation of DippNCO, and also in an alternative reaction leading to the generation of the amino−dicarboxylate complex K2[(NON)Al{κ2−(O,O′)−(O2C)2N‐(Dipp)}] (via the take‐up of a second equivalent of CO2). In the case of benzaldehyde, a similar [2+2] cycloaddition process generates the metallacyclic hemi‐aminal complex, Kn[(NON)Al{κ2−(N,O)−(N(Dipp)C(Ph)(H)O}]n. Extrusion of the imine, PhC(H)NDipp, via cyclo‐reversion is disfavoured thermally, due to the high energy of the putative aluminium oxide co‐product, K2[(NON)Al(O)]2. However, addition of CO2 allows the imine to be released, driven by the formation of the thermodynamically more stable aluminium carbonate co‐product, K2[(NON)Al(κ2−(O,O′)−CO3)]2. [ABSTRACT FROM AUTHOR]

The use of a sterically demanding pincer ligand to prepare an unusual square planar aluminium complex is reported. Due to the constrained geometry imposed by the ligand scaffold, this four-coordinate aluminium centre remains Lewis acidic and reacts via differing metal-ligand cooperative pathways for activating ketones and CO2. It is also a rare example of a single-component aluminium system for the catalytic reduction of CO2 to a methanol equivalent at room temperature. [ABSTRACT FROM AUTHOR]

Caging carbon dioxide: Self ‐ assembled discrete palladium(II) [Pd2(L)4]4+ cages with 2,6 ‐ bis(pyridin ‐ 3 ‐ ylethynyl)pyridine) ligands (L) have cavities, which bind guests containing carbonyl groups through hydrogen bonding interactions. In the solid state these cages have now been shown to bind up to four CO2 molecules, with selectivity over N2. Long ‐ range order in the packing of the molecules in powdered samples of the compound does not appear to be necessary for their activity, making their preparation easy. Additionally, the cages can be readily functionalized, opening up avenues for selective guest binding and gas separations. More information can be found in the Full Paper by B. F. Abrahams, J. D. Crowley et al. on page 10559. [ABSTRACT FROM AUTHOR]

Mn(bpy)‐type complexes bearing local proton source catalyse the electrochemical reduction of CO2. Depending on the strength of the Brønsted acid added to the solution, CO or formate are produced. Spectroelectrochemical studies under Ar and CO2 atmospheres show fast solvolysis and the dimer formation is suppressed, providing an atypical reduction mechanism of MnI catalysts. Spectroscopic evidence of Mn hydride formation supports the existence of different electrocatalytic CO2 reduction pathways. For more information, see the Full Paper by R. Gobetto, C. Nervi et al. on page 4782 ff. [ABSTRACT FROM AUTHOR]

Density functional theory study of the hydrogenation of carbon dioxide to methanol catalyzed by iron, cobalt, and manganese cyclopentadienone complexes reveals a self-promoted mechanism, which features a methanol- or water-molecule-assisted proton transfer for the cleavage of H2. The total free energy barrier of the formation of methanol from CO2 and H2 catalyzed by Knölker's iron cyclopentadienone complex, [2,5-(SiMe3)2-3,4-(CH2)4(η5-C4COH)]Fe(CO)2H, is 26.0 kcal mol−1 in the methanol solvent. We also evaluated the catalytic activities of 8 other experimentally reported iron cyclopentadienone complexes and 37 iron, cobalt, and manganese cyclopentadienone complexes proposed in this study. In general, iron and manganese complexes have relatively higher catalytic activities. Among all calculated complexes, [2,5-(SiMe3)2-3,4-CH3CHSCH2(η5-C4COH)]Fe(CO)2H ( 1Fe-Casey-S-CH3) is the most active one with a total free energy barrier of 25.1 kcal mol−1 in the methanol solvent. Such a low barrier indicates that 1Fe-Casey-S-CH3 is a very promising low-cost and high efficiency catalyst for the conversion of CO2 and H2 to methanol under mild conditions. [ABSTRACT FROM AUTHOR]

Several graphical abstracts of chemistry studies are presented including new approaches to restructure the synthesis of zeolite polymorphs, one on electron paramagnetic resonance (EPR), and one on carbon dioxide sequestration.

Understanding molecular‐scale reaction mechanisms is crucial for the design of modern catalysts with industrial prospect. Through joint experimental and computational studies, we investigate the direct coupling reaction of CH4 and CO2, two abundant greenhouse gases, mediated by Ta1,4+ ions to form larger oxygenated hydrocarbons. Coherent with proposed elementary steps, we expose products of CH4 dehydrogenation [Ta1,4CH2]+ to CO2 in a ring electrode ion trap. Product analysis and reaction kinetics indicate a predisposition of the tetramers for C−O coupling with a conversion to products of CH2O, whereas atomic cations enable C−C coupling yielding CH2CO. Selected experimental findings are supported by thermodynamic computations, connecting structure, electronic properties, and catalyst function. Moreover, the study of bare Ta1,4+ compounds indicates that methane dehydrogenation is a significant initial step in the direct coupling reaction, enabling new, yet unknown reaction pathways. [ABSTRACT FROM AUTHOR]

A pyrazole‐based ligand substituted with terpyridine groups at the 3 and 5 positions has been synthesized to form the dinuclear cobalt complex 1, that electrocatalytically reduces carbon dioxide (CO2) to carbon monoxide (CO) in the presence of Brønsted acids in DMF. Chemical, electrochemical and UV‐vis spectro‐electrochemical studies under inert atmosphere indicate pairwise reduction processes of complex 1. Infrared spectro‐electrochemical studies under CO2 and CO atmosphere are consistent with a reduced CO‐containing dicobalt complex which results from the electroreduction of CO2. In the presence of trifluoroethanol (TFE), electrocatalytic studies revealed single‐site mechanism with up to 94 % selectivity towards CO formation when 1.47 M TFE were present, at −1.35 V vs. Saturated Calomel Electrode in DMF (0.39 V overpotential). The low faradaic efficiencies obtained (<50 %) are attributed to the generation of CO‐containing species formed during the electrocatalytic process, which inhibit the reduction of CO2. [ABSTRACT FROM AUTHOR]

The ultimate fate, over the course of millennia, of nearly all of the carbon dioxide formed by humankind is for it to react with calcium carbonate in the world's oceans. Although, this reaction is of global relevance, aspects of the calcite dissolution reaction remain poorly described with apparent contradictions present throughout the expansive literature. In this perspective we aim to evidence how a lack of appreciation of the role of mass‐transport may have hampered developments in this area. These insights have important implications for both idealised experiments performed under laboratory conditions and for the measurement and modelling of oceanic calcite sediment dissolution. [ABSTRACT FROM AUTHOR]

In this work, the modulation of activity and selectivity via photoreduction of carbon dioxide under simulated sunlight was achieved by treating P25 and P25/Pt NPs with KOH. It found that KOH treatment could significantly improve the overall conversion efficiency and switch the selectivity for CO. Photoelectric characterizations and CO2‐TPD demonstrated that the synergistic effect of K+ and OH‐ accelerated the separation and migration of photogenerated charges, and also improved CO2 adsorption level. Significantly, the K ions could act as active sites for CO2 adsorption and further activation. In situ FTIR measurements and DFT calculations confirmed that K+ enhanced the charge density of adjacent atoms and stabilize CO* groups, reducing the reaction energy barrier and inducing the switching of original CH4 to CO, which played a selective regulatory role. This study provides insights into the photocatalytic activity and selectivity of alkali‐treated photocatalysts and facilitates the design of efficient and product‐specific photocatalysis. [ABSTRACT FROM AUTHOR]

Carbon Dioxide Adsorbents An effective approach to functionalize water ‐ stable metal – organic frameworks (MOFs) by a combination of optimization and metalated ‐ ligand exchange (MLE) for enhanced CO2 separation performance is reported. The optimized UiO ‐ 66(Zr) shows a high BET surface area of 1730 m2 g−1 and a mesopore size of 3.9 nm. The approach described in the Full Paper by D. Zhao and colleagues on page 17246 ff. can enhance both CO2 working capacity and CO2/N2 selectivity simultaneously and thus is an alternative design to achieving water ‐ stable MOFs with high CO2 affinity for efficient CO2 separation. [ABSTRACT FROM AUTHOR]

General strategies for metal aerogel synthesis, including single‐metal, transition‐metal doped, multi‐metal‐doped, and nano‐metal‐doped carbon aerogel are described. In addition, the latest applications of several of the above‐mentioned metal aerogels in electrocatalytic CO2 reduction are discussed. Finally, considering the possibility of future applications of electrocatalytic CO2 reduction technology, a vision for industrialization and directions that can be optimized are proposed. [ABSTRACT FROM AUTHOR]

The development of an efficient strategy for fabricating two‐dimensional metal‐organic framework (MOF) nanosheets with high yield and high stability is desirable. Herein, we demonstrate for the first time that large, single‐layer 2D nickel‐benzene dicarboxylate (Ni−BDC) MOF nanosheets can be fabricated with the assistance of supercritical (SC) CO2 in a pure aqueous system. Detailed experimental evidence reveals that the SC CO2 molecule can exchange with the lattice‐coordinated H2O molecules, side‐on coordinate with the metal Ni1 sites on the Ni−BDC surface, and finally break the interlayer hydrogen bond to exfoliate the bulk Ni−BDC into a 2D MOF. More importantly, a thin SC CO2 layer building up at the water−Ni−BDC interfaces can transform the pristine hydrophilic interface into a super‐hydrophobic one. This super‐hydrophobic layer at the water‐MOF interface can effectively prevent dissociation, thus promoting the stability of Ni−BDC in aqueous system. [ABSTRACT FROM AUTHOR]

Rhodium‐catalyzed acrylate synthesis from CO2 and ethylene was accomplished by using a guanidine‐based NCN pincer ligand. The repulsion between pπ‐electron of guanidine sidearms and occupied dπ orbital of rhodium center raised the level of d‐electrons close to those of formerly known d8‐ruthenium catalyst, thereby promoting the metallalactone formation from carbon dioxide and ethylene. This work fills the absence of group‐9 metal based catalyst for the acrylate synthesis and provides a designing approach for pincer‐ligated d8‐metal catalysts to utilize pπ‐dπ interaction for promoting desirable redox processes. [ABSTRACT FROM AUTHOR]

The reaction of the dilithium salt of the enantiopure (S)‐BINOL (1,1'‐bi‐2‐naphthol) with two equivalents of the amidinate‐stabilized chlorosilylene [LPhSiCl] (LPh=PhC(NtBu)2) led to the formation of the first example of a chiral cyclic silene species comprising an (S)‐BINOL ligand. The reactivity of the Si=C bond was investigated by reaction with elemental sulfur, CO2 and HCl. The reaction with S8 led to a Si=C bond cleavage and concomitantly to a ring‐opened product with imine and silanethione functional groups. The reaction with CO2 resulted in the cleavage of the CO2 molecule into a carbonyl group and an isolated O atom, while a new stereocenter is formed in a highly selective manner. According to DFT calculations, the [2+2] cycloaddition product is the key intermediate. Further reactivity studies of the chiral cyclic silene with HCl resulted in a stereoselective addition to the Si=C bond, while the fully selective formation of two stereocenters was achieved. The quantitative stereoselective addition of CO2 and HCl to a Si=C bond is unprecedented. [ABSTRACT FROM AUTHOR]

A new alkyne‐based hydrocarbon cage was synthesized in high overall yield using alkyne‐alkyne coupling in the cage forming step. The cage is porous and displays a moderately high BET surface area (546 m2 g−1). The cage loses crystallinity on activation and thus is porous in its amorphous form, while very similar cages have been either non‐porous, or retained crystallinity on activation. Reaction of the cage with Co2(CO)8 results in exhaustive metalation of its 12 alkyne groups to give the Co24(CO)72 adduct of the cage in good yield. [ABSTRACT FROM AUTHOR]

Two novel imide/imine‐based organic cages have been prepared and studied as materials for the selective separation of CO2 from N2 and CH4 under vacuum swing adsorption conditions. Gas adsorption on the new compounds showed selectivity for CO2 over N2 and CH4. The cages were also tested as fillers in mixed‐matrix membranes for gas separation. Dense and robust membranes were obtained by loading the cages in either Matrimid® or PEEK‐WC polymers. Improved gas‐transport properties and selectivity for CO2 were achieved compared to the neat polymer membranes. [ABSTRACT FROM AUTHOR]

Simultaneous tuning of permanent porosity and modulation of magnetic properties by postsynthetic modification (PSM) with light in a metal-organic framework is unprecedented. With the aim of achieving such a photoresponsive porous magnetic material, a 3D photoresponsive biporous framework, MOF1, which has 2D channels occupied by the guest 1,2-bis(4-pyridyl)ethylene (bpee), H2O, and EtOH molecules, has been synthesized. The guest bpee in 1 is aligned parallel to pillared bpee with a distance of 3.9 Å between the ethylenic groups; this allows photoinduced PSM of the pore surface through a [2+2] cycloaddition reaction to yield MOF2. Such photoinduced PSM of the framework structure introduces enhanced CO2 selectivity over that of N2. The higher selectivity in MOF2 than that of MOF1 is studied through theoretical calculations. Moreover, MOF2 unveils reversible changes in Tc with response to dehydration-rehydration. This result demonstrates that photoinduced PSM is a powerful tool for fabricating novel functional materials. [ABSTRACT FROM AUTHOR]

Bifunctional metalloporphyrins with quaternary ammonium bromides (nucleophiles) at the meta, para, or ortho positions of meso-phenyl groups were synthesized as catalysts for the formation of cyclic carbonates from epoxides and carbon dioxide under solvent-free conditions. The meta-substituted catalysts exhibited high catalytic performance, whereas the para- and ortho-substituted catalysts showed moderate and low activity, respectively. DFT calculations revealed the origin of the advantage of the meta-substituted catalyst, which could use the flexible quaternary ammonium cation at the meta position to stabilize various anionic species generated during catalysis. A zinc(II) porphyrin with eight nucleophiles at the meta positions showed very high catalytic activity (turnover number (TON)=240 000 at 120 °C, turnover frequency (TOF)=31 500 h−1 at 170 °C) at an initial CO2 pressure of 1.7 MPa; catalyzed the reaction even at atmospheric CO2 pressure (balloon) at ambient temperature (20 °C); and was applicable to a broad range of substrates, including terminal and internal epoxides. [ABSTRACT FROM AUTHOR]

A linear tetracarboxylic acid ligand, H4L, with a pendent amine moiety solvothermally forms two isostructural metal-organic frameworks (MOFs) LM (M=ZnII, CuII). Framework LCu can also be obtained from LZn by post- synthetic metathesis without losing crystallinity. Compared with LZn, the LCu framework exhibits high thermal stability and allows removal of guest solvent and metal-bound water molecules to afford the highly porous, LCu′. At 77 K, LCu′ absorbs 2.57 wt % of H2 at 1 bar, which increases significantly to 4.67 wt % at 36 bar. The framework absorbs substantially high amounts of methane (238.38 cm3 g−1, 17.03 wt %) at 303 K and 60 bar. The CH4 absorption at 303 K gives a total volumetric capacity of 166 cm3 (STP) cm−3 at 35 bar (223.25 cm3 g−1, 15.95 wt %). Interestingly, the NH2 groups in the linker, which decorate the channel surface, allow a remarkable 39.0 wt % of CO2 to be absorbed at 1 bar and 273 K, which comes within the dominion of the most famous MOFs for CO2 absorption. Also, LCu′ shows pronounced selectivity for CO2 absorption over CH4, N2, and H2 at 273 K. The absorbed CO2 can be converted to value-added cyclic carbonates under relatively mild reaction conditions (20 bar, 120 °C). Finally, LCu′ is found to be an excellent heterogeneous catalyst in regioselective 1,3-dipolar cycloaddition reactions ('click' reactions) and provides an efficient, economic route for the one-pot synthesis of structurally divergent propargylamines through three-component coupling of alkynes, amines, and aldehydes. [ABSTRACT FROM AUTHOR]

A table of contents for the issue is presented which discusses topics such as carbonates, carbon dioxide, and lectins.

The formation of supramolecular host-guest complexes is a very useful and widely employed tool in chemistry. However, supramolecular chemistry in non-conventional solvents such as supercritical carbon dioxide (scCO2), one of the most promising sustainable solvents, is still in its infancy. In this work, we explored a successful route to the development of green processes in supercritical CO2 by combining a theoretical approach with experiments. We were able to synthesize and characterize an inclusion complex between a polar aromatic molecule (benzoic acid) and peracetylated-β-cyclodextrin, which is soluble in the supercritical medium. This finding opens the way to wide, environmental friendly, applications of scCO2 in many areas of chemistry, including supramolecular synthesis, reactivity and catalysis, micro and nano-particle formation, molecular recognition, as well as enhanced extraction processes with increased selectivity. [ABSTRACT FROM AUTHOR]

Trans carbamates have been prepared in a diastereoselective approach by a judicious one-pot combination of organic carbonates, prepared in situ, and suitable amine reagents under appropriate reaction conditions. This unprecedented approach allows for stereodivergence from a single oxirane substrate with easy access to both cis and trans carbamate isomers with high stereoselectivity (>19:1 d.r.). Key to the control of the diastereoselective nature of the conversions that lead to the trans carbamates is the in situ formation of trans-configured oligo/polycarbonates through Al catalysis, which provides the targeted products after aminolysis. The present results demonstrate the valorization of a renewable carbon-based reagent (CO2) into new valuable scaffolds and an unusual stereocontrol exerted through carbonate intermediates. A series of control experiments support the proposed mechanistic rationale towards the trans carbamate products, which is based on the trapping of an in situ formed trans-configured oligo/polycarbonate. [ABSTRACT FROM AUTHOR]

The formylation of aryl halides with CO2 to generate aryl aldehydes is challenging. Herein, we report a novel synthesis of aryl aldehydes by formylation of aryl bromides with CO2 and a waste silane, poly(methylhydrosiloxane) (PMHS). It has been discovered that a simple combination of 1,3-bis(diphenyphosphino)propane (DPPP)-chelated Pd catalyst, Pd(DPPP)Cl2, with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is able to effectively catalyze the reaction, leading to aryl aldehydes in moderate to excellent yields, and without any by-products in most cases. Moreover, this route could be extended to the formylation of aryl iodides with high efficiency. This approach is simple, less costly, and environmentally friendly, and also widens the applications of CO2 to form value-added chemicals by the construction of new C−C bonds. [ABSTRACT FROM AUTHOR]

A novel Ag doped Au44(C10H9)28 nanocluster (C10H10=1‐ethynyl‐2,4‐dimethylbenzene) was synthesized, that is, Ag4+xAu40‐x(C10H9)28 (x≤6), where four Ag positions located in the surface staple of the cluster have been determined, while six Au/Ag co‐occupying positions have been found in the metal core of the cluster. The electronic configuration of Au44(C10H9)28 cluster is significantly disturbed by doping Ag atoms, hence promoting the electron transport capability. For the two‐electron conversion reaction of CO2 to CO in electrochemical reduction of CO2, Ag doped Ag4+xAu40‐x(C10H9)28 catalyst exhibited higher effective activity and long‐term stability than its counterpart Au44(C10H9)28 catalyst. [ABSTRACT FROM AUTHOR]

The CO2 reduction reaction (CRR) represents a promising route for the clean utilization of renewable resources. But mass‐transfer limitations seriously hinder the forward step. Enhancing the surface hydrophobicity by using polymers has been proved to be one of the most efficient strategies. However, as macromolecular organics, polymers on the surface hinder the transfer of charge carriers from catalysts to reactants. Herein, we describe an in‐situ surface fluorination strategy to enhance the surface hydrophobicity of TiO2 without a barrier layer of organics, thus facilitating the mass transfer of CO2 to catalysts and charge transfer. With less obstruction to charge transfer, a higher CO2, and lower H+ surface concentration, the photocatalytic CRR generation rate of methanol (CH3OH) is greatly enhanced to up to 247.15 μmol g−1 h−1. Furthermore, we investigated the overall defects; enhancing the surface hydrophobicity of catalysts provides a general and reliable method to improve the competitiveness of CRR. [ABSTRACT FROM AUTHOR]

Carbon cloth electrode modified by covalently attaching a manganese organometallic catalyst is used as cathode for the electrochemical reduction of CO2 in methanol solutions. Six different industrial amines are employed as co‐catalyst in millimolar concentrations to deliver a series of new reactive system. While such absorbents were so far believed to provide a CO2 reservoir and act as sacrificial proton source, we herein demonstrate that this role can be played by methanol, and that the adduct formed between CO2 and the amine can act as an effector or inhibitor toward the catalyst, thereby enhancing or reducing the production of formate. Pentamethyldiethylentriamine (PMDETA), identified as the best effector in our series, converts CO2 in wet methanolic solution into bisammonium bicarbonate. Computational studies revealed that this adduct is responsible for a barrierless transformation of CO2 to formate by the reduced form of the Mn catalyst covalently bonded to the electrode surface. As a consequence, selectivity can be switched on demand from CO to formate anion, and in the case of (PMDETA) an impressive TONHCOO− of 2.8×104 can be reached. This new valuable knowledge on an integrated capture and utilization system paves the way toward more efficient transformation of CO2 into liquid fuel. [ABSTRACT FROM AUTHOR]

With the increasing emission of carbon dioxide (CO2), the conversion and utilization of CO2 have become a topic of increasing concern. Electrochemical CO2 reduction reaction (CO2RR) is an attractive and sustainable approach for solving energy and environmental problems. Design of efficient catalysts is crucial for achieving highly efficient CO2RR. Different methods to prepare catalysts have been reported and used. Among them, electrodeposition is one of the common approaches, which has some obvious advantages, such as requiring simple equipment, environmentally benign. Especially, it can direct deposit catalysts on different substrates to prepare electrodes for CO2RR. In this review, we discuss recent advances in design and preparation of the catalysts by electrodeposition and their applications in CO2RR. Furthermore, the perspective of this promising area is also discussed. [ABSTRACT FROM AUTHOR]