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At the core of carbon monoxide dehydrogenase (CODH) active site two metal ions together with hydrogen bonding scheme from amino acids orchestrate the interconversion between CO2 and CO. We have designed a molecular catalyst implementing a bimetallic iron complex with an embarked second coordination sphere with multi‐point hydrogen‐bonding interactions. We found that, when immobilized on carbon paper electrode, the dinuclear catalyst enhances up to four fold the heterogeneous CO2 reduction to CO in water with an improved selectivity and stability compared to the mononuclear analogue. Interestingly, quasi‐identical catalytic performances are obtained when one of the two iron centers was replaced by a redox inactive Zn metal, questioning the cooperative action of the two metals. Snapshots of X‐ray structures indicate that the two metalloporphyrin units tethered by a urea group is a good compromise between rigidity and flexibility to accommodate CO2 capture, activation, and reduction. [ABSTRACT FROM AUTHOR]

Construction of a "net‐zero‐emission" system through CO2 hydrogenation to methanol with solar energy is an eco‐friendly way to mitigate the greenhouse effect. Traditional CO2 hydrogenation demands centralized mass production for cost reduction with mass water electrolysis for hydrogen supply. To achieve continuous reaction with intermittent and fluctuating flow of H2 on a small‐scale for distributed application scenarios, modulating the catalyst interface environment and chemical adsorption capacity to adapt fluctuating reaction conditions is highly desired. This paper describes a distributed clean CO2 utilization system in which the surface structure of catalysts is carefully regulated. The Ni catalyst with unsaturated electrons loaded on In2O3 can reduce the dissociation energy of H2 to overcome the slow response of intermittent H2 supply, exhibiting a faster response (12 min) than bare oxide catalysts (42 min). Moreover, the introduction of Ni enhances the sensitivity of the catalyst to hydrogen, yielding a Ni/In2O3 catalyst with a good performance at lower H2 concentrations with a 15 times adaptability for wider hydrogen fluctuation range than In2O3, greatly reducing the negative impact of unstable H2 supplies derived from renewable energies. [ABSTRACT FROM AUTHOR]

The concept of green carbon science is to promote the goal of achieving carbon neutrality, the importance and urgency of which have been well‐recognized and received worldwide attention. Carbon neutrality has become the focus of research work in many fields, and correspondingly, a growing number of papers and publications have been published over the last few years. However, since carbon neutralization is a real problem that urgently requires technical solutions, the transition from fundamental research to practical applications must be accelerated. A number of research teams are bold in putting things into practice and blazing new trails. This Review summarizes the recent technological developments within the framework of green carbon science, focusing on conducted pilot tests, industrial demonstrations, and commercial applications beyond the laboratory stage. [ABSTRACT FROM AUTHOR]

The controlled electrochemical reduction of carbon dioxide to value added chemicals is an important strategy in terms of renewable energy technologies. Therefore, the development of efficient and stable catalysts in an aqueous environment is of great importance. In this context, we focused on synthesizing and studying a molecular MnIII‐corrole complex, which is modified on the three meso‐positions with polyethylene glycol moieties for direct and selective production of acetic acid from CO2. Electrochemical reduction of MnIII leads to an electroactive MnII species, which binds CO2 and stabilizes the reduced intermediates. This catalyst allows to electrochemically reduce CO2 to acetic acid in a moderate acidic aqueous medium (pH 6) with a selectivity of 63 % and a turn over frequency (TOF) of 8.25 h−1, when immobilized on a carbon paper (CP) electrode. In terms of high selectivity towards acetate, we propose the formation and reduction of an oxalate type intermediate, stabilized at the MnIII‐corrole center. [ABSTRACT FROM AUTHOR]

The electrochemical CO2 reduction (CO2ER) to multi‐carbon chemical feedstocks over Cu‐based catalysts is of considerable attraction but suffers with the ambiguous nature of active sites, which hinder the rational design of catalysts and large‐scale industrialization. This paper describes a large‐scale simulation to obtain realistic CuZn nanoparticle models and the atom‐level structure of active sites for C2+ products on CuZn catalysts in CO2ER, combining neural network based global optimization and density functional theory calculations. Upon analyzing over 2000 surface sites through high throughput tests based on NN potential, two kinds of active sites are identified, balanced Cu−Zn sites and Zn‐heavy Cu−Zn sites, both facilitating C−C coupling, which are verified by subsequent calculational and experimental investigations. This work provides a paradigm for the design of high‐performance Cu‐based catalysts and may offer a general strategy to identify accurately the atomic structures of active sites in complex catalytic systems. [ABSTRACT FROM AUTHOR]

Electrochemical redox‐control is an emerging strategy for the regulation of polymerization process without the addition of external oxidants and reductants, which enables the control over composition, microstructure and properties of the polymer products. In this paper, based on the chemical selectivity of heterometallic Salen‐Co‐Mn complexes of different valences, an electrochemically switchable strategy was developed for the copolymerization of lactide (LA), CO2 and epoxides. The switchable redox reactions endowed this system with the capability to easily synthesize a multi‐block copolymer of polylactide (PLA) and polycarbonate (PC). Moreover, the multi‐block copolymer could be further modified by introducing various monomers with different microstructures and functional groups. [ABSTRACT FROM AUTHOR]

The design of catalysts with high activity, selectivity, and stability is key to the electroreduction of CO2. Herein, we report the synthesis of 3D hierarchical metal/polymer–carbon paper (M/polymer‐CP) electrodes by in situ electrosynthesis. The 3D polymer layer on CP (polymer‐CP) was first prepared by in situ electropolymerization, then a 3D metal layer was decorated on the polymer‐CP to produce the M/polymer‐CP electrode. Electrodes with different metals (e.g. Cu, Pd, Zn, Sn) and various polymers could be prepared by this method. The electrodes could efficiently reduce CO2 to desired products, such as C2H4, CO, and HCOOH, depending on the metal used. For example, C2H4 could be formed with a Faradaic efficiency of 59.4 % and a current density of 30.2 mA cm−2 by using a very stable Cu/PANI‐CP electrode in an H‐type cell. Control experiments and theoretical calculations showed that the 3D hierarchical structure of the metals and in situ formation of the electrodes are critical for the excellent performance. [ABSTRACT FROM AUTHOR]

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Methanol is a very useful platform molecule and liquid fuel. Electrocatalytic reduction of CO2 to methanol is a promising route, which currently suffers from low efficiency and poor selectivity. Herein we report the first work to use a Mo-Bi bimetallic chalcogenide (BMC) as an electrocatalyst for CO2 reduction. By using the Mo-Bi BMC on carbon paper as the electrode and 1-butyl-3-methylimidazolium tetrafluoroborate in MeCN as the electrolyte, the Faradaic efficiency of methanol could reach 71.2 % with a current density of 12.1 mA cm−2, which is much higher than the best result reported to date. The superior performance of the electrode resulted from the excellent synergistic effect of Mo and Bi for producing methanol. The reaction mechanism was proposed and the reason for the synergistic effect of Mo and Bi was discussed on the basis of some control experiments. This work opens a way to produce methanol efficiently by electrochemical reduction of CO2. [ABSTRACT FROM AUTHOR]

Adsorption‐based removal of carbon dioxide (CO2) from gas mixtures has demonstrated great potential for solving energy security and environmental sustainability challenges. However, due to similar physicochemical properties between CO2 and other gases as well as the co‐adsorption behavior, the selectivity of CO2 is severely limited in currently reported CO2‐selective sorbents. To address the challenge, we create a bioinspired design strategy and report a robust, microporous metal–organic framework (MOF) with unprecedented [Mn86] nanocages. Attributed to the existence of unique enzyme‐like confined pockets, strong coordination interactions and dipole‐dipole interactions are generated for CO2 molecules, resulting in only CO2 molecules fitting in the pocket while other gas molecules are prohibited. Thus, this MOF can selectively remove CO2 from various gas mixtures and show record‐high selectivities of CO2/CH4 and CO2/N2 mixtures. Highly efficient CO2/C2H2, CO2/CH4, and CO2/N2 separations are achieved, as verified by experimental breakthrough tests. This work paves a new avenue for the fabrication of adsorbents with high CO2 selectivity and provides important guidance for designing highly effective adsorbents for gas separation. [ABSTRACT FROM AUTHOR]

Photocatalytic CO2 reduction (PCR) expresses great attraction to convert useless greenhouse gas into valuable chemical feedstock. However, the weak interactions between catalytic sites and PCR intermediates constrains the PCR activity and selectivity. Herein, we proposed a new strategy to match the intermediates due to the maximum orbital overlap of catalytic sites and C1 intermediates by establishing dual Jahn–Teller (J–T) sites, in which, the strongly asymmetric J–T sites can break the nonpolar CO2 molecules and self‐adapt the different structure of C1 intermediates. Taking cobalt carbonate hydroxide as an example, the weakly symmetric dual cobalt (Co2) dual J–T sites, weakly asymmetric Fe&Co sites and strongly asymmetric Cu&Co sites were assembled. After illumination, the interaction between dual J–T sites and the CO2 molecules enhances J–T distortion, which further modulates the PCR activity and selectivity. As a result, the Cu&Co sites exhibited CO yield of 8137.9 μmol g−1, about 2.3‐fold and 4.2‐fold higher than that of the Fe&Co and Co2 sites within 5‐hour photoreaction, respectively. In addition, the selectivity achieved as high as 92.62 % than Fe&Co (88.67 %) and Co2 sites (55.33 %). This work provides a novel design concept for the construction of dual J–T sites to regulate the catalytic activity and selectivity. [ABSTRACT FROM AUTHOR]

Here we show that a tridentate bis(aryloxide)anilide‐ligated titanium/potassium scaffold promotes functionalization of coordinated N2 with CO2 and CS2 through formation of N−C bonds. Treatment of a naphthalene complex with N2 gave an end‐on bridging dinitrogen complex featuring a [Ti2K2N2] core. The dinitrogen complex underwent insertion of CO2 into each Ti−NN bond to afford an N,N′‐dicarboxylated hydrazido complex. Stepwise nitrogen‐carbon bond formation at coordinated N2 proceeded to afford an unsymmetric hydrazido complex upon sequentially treating the dinitrogen complex with CS2 and CO2. Addition of Me3SiCl to the dicarboxylated hydrazido complex resulted in partial silylation of the carboxylate groups but did not lead to removal of the functionalized N2 unit from the metal centers. However, reduction of the dicarboxylated hydrazido complex with potassium naphthalenide afforded an oxo‐bridged dinuclear complex along with release of free potassium cyanate. [ABSTRACT FROM AUTHOR]

Mechanistic studies of substrate insertion into dimeric [(NHC)CuH]2 (NHC=N‐heterocyclic carbene) complexes with two bridging hydrides have been shown to require dimer dissociation to generate transient, highly reactive (NHC)Cu−H monomers in solution. Using single‐crystal to single‐crystal (SC‐SC) transformations, we discovered a new pathway of stepwise insertion of CO2 into [(NHC)CuH]2 without complete dissociation of the dimer. The first CO2 insertion into dimeric [(IPr*OMe)CuH]2 (IPr*OMe=N,N′‐bis(2,6‐bis(diphenylmethyl)‐4‐methoxy‐phenyl)imidazole‐2‐ylidene) produced a dicopper formate hydride [(IPr*OMe)Cu]2(μ‐1,3‐O2CH)(μ‐H). A second CO2 insertion produced a dicopper bis(formate), [(IPr*OMe)Cu]2(μ‐1,3‐O2CH)(μ‐1,1‐O2CH), containing two different bonding modes of the bridging formate. These dicopper formate complexes are inaccessible from solution reactions since the dicopper core cleanly ruptures to monomeric complexes when dissolved in a solvent. [ABSTRACT FROM AUTHOR]

Carboxylation of easily available alkenes with CO2 is highly important to afford value‐added carboxylic acids. Although dicarboxylation of activated alkenes, especially 1,3‐dienes, has been widely investigated, the challenging dicarboxylation of unactivated 1,n‐dienes (n>3) with CO2 remains unexplored. Herein, we report the first dicarboxylation of unactivated skipped dienes with CO2 via electrochemistry, affording valuable dicarboxylic acids. Control experiments and DFT calculations support the single electron transfer (SET) reduction of CO2 to its radical anion, which is followed by sluggish radical addition to unactivated alkenes, SET reduction of unstabilized alkyl radicals to carbanions and nucleophilic attack on CO2 to give desired products. This reaction features mild reaction conditions, broad substrate scope, facile derivations of products and promising application in polymer chemistry. [ABSTRACT FROM AUTHOR]

Natural photosynthesis (NP) generates oxygen and carbohydrates from water and CO2 utilizing solar energy to nourish lives and balance CO2 levels. Following nature, artificial photosynthesis (AP), typically, overall water or CO2 splitting, produces fuels and chemicals from renewable energy. However, hydrogen evolution or CO2 reduction is inherently coupled with kinetically sluggish water oxidation, lowering efficiencies and raising safety concerns. Decoupled systems have thus emerged. In this review, we elaborate how decoupled artificial photosynthesis (DAP) evolves from NP and AP and unveil their distinct photoelectrochemical mechanisms in energy capture, transduction and conversion. Advances of AP and DAP are summarized in terms of photochemical (PC), photoelectrochemical (PEC), and photovoltaic‐electrochemical (PV‐EC) catalysis based on material and device design. The energy transduction process of DAP is emphasized. Challenges and perspectives on future researches are also presented. [ABSTRACT FROM AUTHOR]

Abstract: In situ and operando spectroscopic and microscopic methods were used to gain insight into the correlation between the structure, chemical state, and reactivity of size‐ and shape‐controlled ligand‐free Cu nanocubes during CO2 electroreduction (CO2RR). Dynamic changes in the morphology and composition of Cu cubes supported on carbon were monitored under potential control through electrochemical atomic force microscopy, X‐ray absorption fine‐structure spectroscopy and X‐ray photoelectron spectroscopy. Under reaction conditions, the roughening of the nanocube surface, disappearance of the (100) facets, formation of pores, loss of Cu and reduction of CuOx species observed were found to lead to a suppression of the selectivity for multi‐carbon products (i.e. C2H4 and ethanol) versus CH4. A comparison with Cu cubes supported on Cu foils revealed an enhanced morphological stability and persistence of CuI species under CO2RR in the former samples. Both factors are held responsible for the higher C2/C1 product ratio observed for the Cu cubes/Cu as compared to Cu cubes/C. Our findings highlight the importance of the structure of the active nanocatalyst but also its interaction with the underlying substrate in CO2RR selectivity. [ABSTRACT FROM AUTHOR]

The development of efficient electrocatalysts with non‐copper metal sites for electrochemical CO2 reduction reactions (eCO2RR) to hydrocarbons and oxygenates is highly desirable, but still a great challenge. Herein, a stable metal–organic framework (DMA)4[Sn2(THO)2] (Sn‐THO, THO6− = triphenylene‐2,3,6,7,10,11‐hexakis(olate), DMA = dimethylammonium) with isolated and distorted octahedral SnO62− active sites is reported as an electrocatalyst for eCO2RR, showing an exceptional performance for eCO2RR to the CH4 product rather than the common products formate and CO for reported Sn‐based catalysts. The partial current density of CH4 reaches a high value of 34.5 mA cm−2, surpassing most reported copper‐based and all non‐Cu metal‐based catalysts. Our experimental and theoretical results revealed that the isolated SnO62− active site favors the formation of key *OCOH species to produce CH4 and can greatly inhibit the formation of *OCHO and *COOH species to produce *HCOOH and *CO, respectively. [ABSTRACT FROM AUTHOR]

Polyurethanes (PUs) are a class of materials usually synthesized from isocyanates, diols, and water. Water is essential for producing carbon dioxide (CO2) which is used for the self‐blowing of the foams. Due to safety concerns with the production of isocyanates, alternative chemistries have been evaluated and cyclic carbonate systems have shown great promise. In a recent advancement by Bourguignon, Grignard, and Detrembleur, a cyclic carbonate and diamine system is capable of generating CO2 for self‐blowing through hydrolysis of the carbonate‐based monomer. The authors demonstrate that with a simple variation of the diamine monomer a wide range of physical and thermo‐mechanical properties were achievable. This work represents a significant step towards safer and more environmentally friendly PUs. [ABSTRACT FROM AUTHOR]

A series of manganese polypyridine complexes were prepared as CO2 reduction electrocatalysts. Among these catalysts, the intramolecular proton tunneling distance for metal hydride formation (PTD‐MH) vary from 2.400 to 2.696 Å while the structural, energetic, and electronic factors remain essentially similar to each other. The experimental and theoretical results revealed that the selectivity of CO2 reduction reaction (CO2RR) is dominated by the intramolecular PTD‐MH within a difference of ca. 0.3 Å. Specifically, the catalyst functionalized with a pendent phenol group featuring a slightly longer PTD‐MH favors the binding of proton to the [Mn−CO2] adduct rather than the Mn center and results in ca. 100 % selectivity for CO product. In contrast, decreasing the PTD‐MH by attaching a dangling tertiary amine in the same catalyst skeleton facilitates the proton binding on the Mn center and switches the product from CO to HCOOH with a selectivity of 86 %. [ABSTRACT FROM AUTHOR]

Gas‐liquid‐solid triple‐phase interfaces (TPI) are essential for promoting electrochemical CO2 reduction, but it remains challenging to maximize their efficiency while integrating other desirable properties conducive to electrocatalysis. Herein, we report the elaborate design and fabrication of a superhydrophobic, conductive, and hierarchical wire membrane in which core–shell CuO nanospheres, carbon nanotubes (CNT), and polytetrafluoroethylene (PTFE) are integrated into a wire structure (designated as CuO/F/C(w); F, PTFE; C, CNT; w, wire) to maximize their respective functions. The realized architecture allows almost all CuO nanospheres to be exposed with effective TPI and good contact to conductive CNT, thus increasing the local CO2 concentration on the CuO surface and enabling fast electron/mass transfer. As a result, the CuO/F/C(w) membrane attains a Faradaic efficiency of 56.8 % and a partial current density of 68.9 mA cm−2 for multicarbon products at −1.4 V (versus the reversible hydrogen electrode) in the H‐type cell, far exceeding 10.1 % and 13.4 mA cm−2 for bare CuO. [ABSTRACT FROM AUTHOR]

A conceptually novel catalytic domino approach is presented for the synthesis of highly functional 1,4‐dihydro‐2H‐1,3‐benzoxazine‐2‐one derivatives. Key to the chemoselectivity is a proper design of the precursor to override thermodynamically favored parasitic cyclization processes and empower the formation of the desired product through Thorpe–Ingold effects. The synthetic diversity of these CO2‐based heterocycles is further demonstrated, and the isolation of a reaction intermediate supports an unusual ring‐expansion sequence from an α‐alkylidene, five‐membered cyclic carbonate to a six‐membered cyclic carbamate by N‐induced isomerization. [ABSTRACT FROM AUTHOR]

It is highly desired to achieve controllable product selectivity in CO2 hydrogenation. Herein, we report light‐induced switching of reaction pathways of CO2 hydrogenation towards CH3OH production over actomically dispersed Co decorated Pt@UiO‐66‐NH2. CO, being the main product in the reverse water gas shift (RWGS) pathway under thermocatalysis condition, is switched to CH3OH via the formate pathway with the assistance of light irradiation. Impressively, the space‐time yield of CH3OH in photo‐assisted thermocatalysis (1916.3 μmol gcat−1 h−1) is about 7.8 times higher than that without light at 240 °C and 1.5 MPa. Mechanism investigation indicates that upon light irradiation, excited UiO‐66‐NH2 can transfer electrons to Pt nanoparticles and Co sites, which can efficiently catalyze the critical elementary steps (i.e. CO2‐to‐*HCOO conversion), thus suppressing the RWGS pathway to achieve a high CH3OH selectivity. [ABSTRACT FROM AUTHOR]

Immobilization of porphyrin complexes into crystalline metal–organic frameworks (MOFs) enables high exposure of porphyrin active sites for CO2 electroreduction. Herein, well‐dispersed iron‐porphyrin‐based MOF (PCN‐222(Fe)) on carbon‐based electrodes revealed optimal turnover frequencies for CO2 electroreduction to CO at 1 wt.% catalyst loading, beyond which the intrinsic catalyst activity declined due to CO2 mass transport limitations. In situ Raman suggested that PCN‐222(Fe) maintained its structure under electrochemical bias, permitting mechanistic investigations. These revealed a stepwise electron transfer‐proton transfer mechanism for CO2 electroreduction on PCN‐222(Fe) electrodes, which followed a shift from a rate‐limiting electron transfer to CO2 mass transfer as the potential increased from −0.6 V to −1.0 V vs. RHE. Our results demonstrate how intrinsic catalytic investigations and in situ spectroscopy are needed to elucidate CO2 electroreduction mechanisms on PCN‐222(Fe) MOFs. [ABSTRACT FROM AUTHOR]

The development of efficient electrocatalysts to generate key *NH2 and *CO intermediates is crucial for ambient urea electrosynthesis with nitrate (NO3−) and carbon dioxide (CO2). Here we report a liquid‐phase laser irradiation method to fabricate symbiotic graphitic carbon encapsulated amorphous iron and iron oxide nanoparticles on carbon nanotubes (Fe(a)@C‐Fe3O4/CNTs). Fe(a)@C‐Fe3O4/CNTs exhibits superior electrocatalytic activity toward urea synthesis using NO3− and CO2, affording a urea yield of 1341.3±112.6 μg h−1 mgcat−1 and a faradic efficiency of 16.5±6.1 % at ambient conditions. Both experimental and theoretical results indicate that the formed Fe(a)@C and Fe3O4 on CNTs provide dual active sites for the adsorption and activation of NO3− and CO2, thus generating key *NH2 and *CO intermediates with lower energy barriers for urea formation. This work would be helpful for design and development of high‐efficiency dual‐site electrocatalysts for ambient urea synthesis. [ABSTRACT FROM AUTHOR]

Herein, a direct, metal‐free, and site‐selective electrochemical C−H carboxylation of arenes by reductive activation using CO2 as the economic and abundant carboxylic source was reported. The electrocarboxylation was carried out in an operationally simple manner with high chemo‐ and regioselectivity, setting the stage for the challenging site‐selective C−H carboxylation of unactivated (hetero)arenes. The robust nature of the electrochemical strategy was reflected by a broad scope of substrates with excellent atom economy and unique selectivity. Notably, the direct and selective C−H carboxylation of various challenging arenes worked well in this approach, including electron‐deficient naphthalenes, pyridines, simple phenyl derivatives, and substituted quinolines. The method benefits from being externally catalyst‐free, metal‐free and base‐free, which makes it extremely attractive for potential applications. [ABSTRACT FROM AUTHOR]

For 80 years, polyisocyanates and polyols were central building blocks for the industrial fabrication of polyurethane (PU) foams. By their partial hydrolysis, isocyanates release CO2 that expands the PU network. Substituting this toxic isocyanate‐based chemistry by a more sustainable variant—that in situ forms CO2 by hydrolysis of a comonomer—is urgently needed for producing greener cellular materials. Herein, we report a facile, up‐scalable process, potentially compatible to existing infrastructures, to rapidly prepare water‐induced self‐blown non‐isocyanate polyurethane (NIPU) foams. We show that formulations composed of poly(cyclic carbonate)s and polyamines furnish rigid or flexible NIPU foams by partial hydrolysis of cyclic carbonates in the presence of a catalyst. By utilizing readily available low cost starting materials, this simple but robust process gives access to greener PU foams, expectedly responding to the sustainability demands of many sectors. [ABSTRACT FROM AUTHOR]

Fatty acid photodecarboxylase is a newly discovered flavin photoenzyme that converts a carboxylic acid into a hydrocarbon and a carbon dioxide molecule through decarboxylation. The enzymatic reactions are poorly understood. In this study, we carefully characterized its dynamic evolution with femtosecond spectroscopy. We observed initial electron transfer from the substrate to the flavin cofactor in 347 ps with a stretched dynamic behavior and subsequently captured the critical carbonyloxy radical. The dominant process following this step was decarboxylation in 5.8 ns to form an alkyl radical and a carbon dioxide molecule. We further identified the absorption bands of two carbonyloxy and alkyl radical intermediates. The overall enzymatic quantum efficiency determined by our obtained timescales is 0.81, consistent with the steady‐state value. The results are essential to the elucidation of the enzyme mechanism and catalytic photocycle, providing a molecular basis for potential design of flavin‐based artificial photoenzymes. [ABSTRACT FROM AUTHOR]

Catalysis is involved in around 85 % of manufacturing industry and contributes an estimated 25 % to the global domestic product, with the majority of the processes relying on heterogeneous catalysis. Despite the importance in different global segments, the fundamental understanding of heterogeneously catalysed processes lags substantially behind that achieved in other fields. The newly established Max Planck–Cardiff Centre on the Fundamentals of Heterogeneous Catalysis (FUNCAT) targets innovative concepts that could contribute to the scientific developments needed in the research field to achieve net zero greenhouse gas emissions in the chemical industries. This Viewpoint Article presents some of our research activities and visions on the current and future challenges of heterogeneous catalysis regarding green industry and the circular economy by focusing explicitly on critical processes. Namely, hydrogen production, ammonia synthesis, and carbon dioxide reduction, along with new aspects of acetylene chemistry. [ABSTRACT FROM AUTHOR]

Although pure and functionalized solid‐state polyniobates such as layered perovskites and niobate nanosheets are photocatalysts for renewable‐energy processes, analogous reactions by molecular polyoxoniobate cluster‐anions are nearly absent from the literature. We now report that under simulated solar light, hexaniobate cluster‐anion encapsulated 30‐NiII‐ion "fragments" of surface‐protonated cubic‐phase‐like NiO cores activate the hexaniobate ligands towards CO2 reduction by water. Photoexcitation of the NiO cores promotes charge‐transfer reduction of NbV to NbIV, increasing electron density at bridging oxo atoms of Nb‐μ‐O‐Nb linkages that bind and convert CO2 to CO. Photogenerated NiO "holes" simultaneously oxidize water to dioxygen. The findings point to molecular complexation of suitable semiconductor "fragments" as a general method for utilizing electron‐dense polyoxoniobate anions as nucleophilic photocatalysts for solar‐light driven activation and reduction of small molecules. [ABSTRACT FROM AUTHOR]

The carbon dioxide (CO2) capture and utilization has attracted a great attention in organic synthesis. Herein, an unpresented transient stabilization effect (TSE) of CO2 is disclosed and well applied to the electrochemical hydrogenation of azo compounds to hydrazine derivatives. Mechanistic experiments and computational studies imply that CO2 can capture azo radical anion intermediates to protect the hydrogenation from potential degradation reactions, and is finally released through decarboxylation. The promotion effect of CO2 was further demonstrated to work in the preliminary study of electrochemical reductive coupling of α‐ketoesters to vicinal diol derivatives. For the electrochemical reductive reactions mentioned above, CO2 is indispensable. The presented results shed light on a different usage of CO2 and could inspire novel experimental design by using CO2 as a transient protecting group. [ABSTRACT FROM AUTHOR]

Carboxyl group is one of the most widely used groups in organic synthesis. Herein, an efficient copper‐catalyzed carboxylation of aryl thianthrenium salts with carbon dioxide (CO2) at room temperature has been developed. The reaction employs low loading of cuprous chloride catalyst under 1 atm CO2 and exhibits good functional group tolerance. In combination with C−H thianthrenation of aromatic hydrocarbons, this work provides an efficient method for the site‐selective C−H carboxylation of aromatic hydrocarbons. It may serve as a significant late‐stage carboxylation tool for the modification of drug molecules in the future. [ABSTRACT FROM AUTHOR]

Formaldehyde (HCHO) is a crucial C1 building block for daily‐life commodities in a wide range of industrial processes. Industrial production of HCHO today is based on energy‐ and cost‐intensive gas‐phase catalytic oxidation of methanol, which calls for exploring other and more sustainable ways of carrying out this process. Utilization of carbon dioxide (CO2) as precursor presents a promising strategy to simultaneously mitigate the carbon footprint and alleviate environmental issues. This Minireview summarizes recent progress in CO2‐to‐HCHO conversion using hydrogenation, hydroboration/hydrosilylation as well as photochemical, electrochemical, photoelectrochemical, and enzymatic approaches. The active species, reaction intermediates, and mechanistic pathways are discussed to deepen the understanding of HCHO selectivity issues. Finally, shortcomings and prospects of the various strategies for sustainable reduction of CO2 to HCHO are discussed. [ABSTRACT FROM AUTHOR]

The electrocatalytic CO2 reduction reaction (ECO2RR) is one promising method for storing intermittent clean energy in chemical bonds and producing fuels. Among various kinds of catalysts for ECO2RR, molecular metal complexes with well‐defined structures are convenient for studies of their rational design, structure–reactivity relationships, and mechanisms. In this Review, we summarize the molecular engineering of several N‐based metal complexes including Re/Mn bipyridine compounds and metal macrocycles, concluding with general modification strategies to devise novel molecular catalysts with high intrinsic activity. Through physical adsorption, covalent linking, and formation of a periodic backbone, these active molecules can be heterogenized into immobilized catalysts with more practical prospects. Finally, significant challenges and opportunities based on molecular catalysts are discussed. [ABSTRACT FROM AUTHOR]

Bimetallic motifs mediate the selective activation and functionalization of CO2 in metalloenzymes and some recent synthetic systems. In this work, we build on the nascent concept of bimetallic frustrated Lewis pairs (FLPs) to investigate the activation and reduction of CO2. Using the Fe0 fragment [(depe)2Fe] (depe=1,2‐bis(diethylphosphino)ethane) as base, we modify the nature of the partner Lewis acid to accomplish a divergent and highly chemoselective reactivity towards CO2. [Au(PMe2Ar)]+ irreversibly dissociates CO2, Zn(C6F5)2 and B(C6F5)3 yield different CO2 adducts stabilized by push‐pull interactions, while Al(C6F5)3 leads to a rare heterobimetallic C−O bond cleavage, and thus to contrasting reduced products after exposure to dihydrogen. Computational investigations provide a rationale for the divergent reactivity, while Energy Decomposition Analysis‐Natural Orbital for Chemical Valence (EDA‐NOCV) method substantiates the heterobimetallic bonding situation. [ABSTRACT FROM AUTHOR]

Free N‐heterocyclic carbenes (NHCs) are generally prepared by treatment of imidazolium precursors with strong alkali reagents, which usually produces inactive NHC dimers. This treatment would destroy porous supports and thus make supported NHC catalysts difficult to recovery and reuse. Herein, we report the first stable CO2‐masked N‐heterocyclic carbenes (NHCs) grafted on a porous crystalline covalent organic framework (COF). The stable NHC‐CO2 moieties in the COF‐NHC‐CO2 could be transformed in situ into isolated NHCs by heating, which exhibit superior catalytic performances in hydrosilylation and N‐formylation reactions with CO2. The NHC sites can reversibly form NHC‐CO2 and thus can be easily recycled and reused while maintaining excellent catalytic activity. Density functional theory calculations revealed that NHC sites can be fully exposed after removal of CO2‐masks and rapidly react with silanes, which endows COF‐NHC with high catalytic activity. [ABSTRACT FROM AUTHOR]

The engineering and tailoring of porous materials to realize the precise discrimination of CO2 and C2H2, with almost identical kinetic diameters, is a challenging task. We herein report the first example of the kinetic‐sieving of relatively larger molecule of C2H2 from CO2 by a novel sulfonic anion‐pillared hybrid ultramicroporous materials of ZU‐610a. Specifically, ZU‐610 constructed from copper(II), isonicotinic acid and 1,2‐ethanedisulfonic acid is synthesized and shows the preferential affinity for C2H2 over CO2. After the post‐synthetic heat treatment of ZU‐610, ZU‐610a with a contracted aperture is obtained. Interestingly, the C2H2‐selctive ZU‐610 was reversed to the CO2‐selective ZU‐610a. High purity C2H2 (>99.5 %) could be directly obtained from the dynamic breakthrough experiments on an equimolar C2H2/CO2 mixture at 298 K. This study provides guidance for the design of adsorbents aimed at separation systems with similar kinetic diameter. [ABSTRACT FROM AUTHOR]

Rather than just focusing on the catalyst itself in the electrocatalytic CO2 reduction reaction (eCO2RR), as previously reviewed elsewhere, we herein extend the discussion to the special topic of the microenvironment around the electrocatalytic center and present a comprehensive overview of recent research progress. We categorize the microenvironment based on the components relevant to electrocatalytic active sites, i.e. the catalyst surface, substrate, co‐reactants, electrolyte, membrane, and reactor. Supported by most of the reported articles, the relevant factors affecting the catalytic performance of eCO2RR are then discussed in detail, and existing challenges and potential solutions are mentioned. Perspectives for the future research on eCO2RR, including the integration of different microenvironment factors, the extension to industrial application by coupling with carbon capture and conversion, and separation of products, are also discussed. [ABSTRACT FROM AUTHOR]

Diene‐transmissive hetero‐Diels–Alder sequences involving carbonyl dienophiles are reported for the first time. High enantioselectivities are achieved in the reaction of phenylglyoxal with a broad range of dendralene structures, through the optimization of a Pd2+ catalyst system. The initial catalyst‐controlled enantioselective oxa‐Diels–Alder (ODA) cycloaddition to a [3]dendralene generates a dihydropyran carrying a semicyclic diene. This participates in a subsequent catalyst or substrate‐controlled Diels–Alder reaction to generate sp3‐rich fused polycyclic systems containing both heterocycles and carbocycles. Computational investigations reveal a concerted asynchronous mechanism. π‐Complexation of a diene C=C bond to Pd2+ occurs in both the pre‐transition state (TS) complex and in cycloaddition TSs, controlling stereoselectivity. A formal enantioselective [4+2]cycloaddition of a CO2 dienophile is demonstrated. [ABSTRACT FROM AUTHOR]

Electroreduction of CO2 to acetate provides a promising strategy to reduce CO2 emissions and store renewable energy, but acetate is usually a by‐product. Here, we show a stable and conductive two‐dimensional phthalocyanine‐based covalent‐organic framework (COF) as an electrocatalyst for reduction of CO2 to acetate with a single‐product Faradaic efficiency (FE) of 90.3(2)% at −0.8 V (vs. RHE) and a current density of 12.5 mA cm−2 in 0.1 M KHCO3 solution. No obvious degradation was observed over 80 hours of continuous operation. Combined with the comparison of the properties of other catalysts with isolated metal active sites, theoretical calculations and in situ infrared spectroscopy revealed that the isolated copper‐phthalocyanine active site with high electron density is conducive to the key step of C−C coupling of *CH3 with CO2 to produce acetate, and can avoid the coupling of *CO with *CO or *CHO to produce ethylene and ethanol. [ABSTRACT FROM AUTHOR]

Although pyrazine‐linked hybrid ultramicroporous materials (HUMs, pore size <7 Å) are benchmark physisorbents for trace carbon dioxide (CO2) capture under dry conditions, their affinity for water (H2O) mitigates their carbon capture performance in humid conditions. Herein, we report on the co‐adsorption of H2O and CO2 by TIFSIX‐3‐Ni—a high CO2 affinity HUM—and find that slow H2O sorption kinetics can enable CO2 uptake and release using shortened adsorption cycles with retention of ca. 90 % of dry CO2 uptake. Insight into co‐adsorption is provided by in situ infrared spectroscopy and ab initio calculations. The binding sites and sorption mechanisms reveal that both CO2 and H2O molecules occupy the same ultramicropore through favorable interactions between CO2 and H2O at low water loading. An energetically favored water network displaces CO2 molecules at higher loading. Our results offer bottom‐up design principles and insight into co‐adsorption of CO2 and H2O that is likely to be relevant across the full spectrum of carbon capture sorbents to better understand and address the challenge posed by humidity to gas capture. [ABSTRACT FROM AUTHOR]

A new catalytic route has been developed for the coupling of epoxides and CO2 affording polymerizable six‐membered bicyclic carbonates. Cyclic epoxides equipped with a β‐positioned OH group can be transformed into structurally diverse bicyclic cyclic carbonates in good yields and with high selectivity. Key to the chemo‐selectivity is the difference between the reactivity of syn‐ and anti‐configured epoxy alcohols, with the latter leading to six‐membered ring carbonate formation in the presence of a binary AlIII aminotriphenolate complex/DIPEA catalyst. X‐ray analyses show that the conversion of the syn‐configured substrate evolves via a standard double inversion pathway providing a five‐membered carbonate product, whereas the anti‐isomer allows for activation of the oxirane unit of the substrate opposite to the pendent alcohol. The potential use of these bicyclic products is shown in ring‐opening polymerization offering access to rigid polycarbonates with improved thermal resistance. [ABSTRACT FROM AUTHOR]

Electroreduction of CO2 into valuable fuels and feedstocks offers a promising way for CO2 utilization. However, the commercialization is limited by the low productivity. Here, we report a strategy to enhance the productivity of CO2 electroreduction by improving diffusion of CO2 to the surface of catalysts using porous organic cages (POCs) as an additive. It was noted that the Faradaic efficiency (FE) of C2+ products could reach 76.1 % with a current density of 1.7 A cm−2 when Cu‐nanorod(nr)/CC3 (one of the POCs) was used, which were much higher than that using Cu‐nr. Detailed studies demonstrated that the hydrophobic pores of CC3 can adsorb a large amount of CO2 for the reaction, and the diffusion of CO2 in the CC3 to the nanocatalyst surface is easier than that in the liquid electrolyte. Thus, more CO2 molecules make contact with the nanocatalysts in the presence of CC3, enhancing CO2 reduction and inhibiting generation of H2. [ABSTRACT FROM AUTHOR]

Frontispiz: Demonstrating and Unraveling a Controlled Nanometer-Scale Expansion of the Vacancy Defects in Graphene by CO2 CO2 Based Etching, Grain-Boundary Defects, Intrinsic Vacancy Defects, Single-Layer Graphene, Vacancy Defects, Vacancy Expansion, Vacancy Nucleation Keywords: CO2 Based Etching; Grain-Boundary Defects; Intrinsic Vacancy Defects; Single-Layer Graphene; Vacancy Defects; Vacancy Expansion; Vacancy Nucleation EN CO2 Based Etching Grain-Boundary Defects Intrinsic Vacancy Defects Single-Layer Graphene Vacancy Defects Vacancy Expansion Vacancy Nucleation 1 1 1 04/18/22 20220425 NES 220425 B Graphen b In ihrem Forschungsartikel (e202200321) demonstrieren Kumar Varoon Agrawal et al. [Extracted from the article]

The conversion of CO2 into multicarbon (C2+) compounds by reductive homocoupling offers the possibility to transform renewable energy into chemical energy carriers and thereby create "carbon‐neutral" fuels or other valuable products. Most available studies have employed heterogeneous metallic catalysts, but the use of molecular catalysts is still underexplored. However, several studies have already demonstrated the great potential of the molecular approach, namely, the possibility to gain a deep mechanistic understanding and a more precise control of the product selectivity. This Minireview summarizes recent progress in both the thermo‐ and electrochemical reductive homocoupling of CO2 toward C2+ products mediated by molecular catalysts. In addition, reductive CO homocoupling is discussed as a model for the further conversion of intermediates obtained from CO2 reduction, which may serve as a source of inspiration for developing novel molecular catalysts in the future. [ABSTRACT FROM AUTHOR]

A tritopic, Ni‐substituted Keggin cluster, {SiW9Ni4}, assembles with rigid dicarboxylate linkers to give rise to a set of discrete, POM2nL3n‐type structures (POM={SiW9Ni4}) with defined interior voids. The outcome of coordination‐driven self‐assemblies of these polyhedral cages—from fused dimers to trigonal prisms—was found to be sensitive to bend angles of the ditopic ligands, which vary from 122° to 180°. These polyoxotungstate‐based metal–organic polyhedra, when coupled with [Ru(bpy)3]Cl2 as a photosensitizer and triethanolamine as the electron donor, serve as highly effective catalysts for CO2 reduction, with turnover numbers up to 328 and CO selectivity as high as 96.2 %. The inner cavities of such cage structures, if functionalized or of sufficient size to encapsulate targeted guest molecules, could present a new strategy towards functional materials for potential applications. [ABSTRACT FROM AUTHOR]

A controlled manipulation of graphene edges and vacancies is desired for molecular separation, sensing and electronics applications. Unfortunately, available etching methods always lead to vacancy nucleation making it challenging to control etching. Herein, we report CO2‐led controlled etching down to 2–3 Å per minute while completely avoiding vacancy nucleation. This makes CO2 a unique etchant for decoupling pore nucleation and expansion. We show that CO2 expands the steric‐hindrance‐free edges with an activation energy of 2.71 eV, corresponding to the energy barrier for the dissociative chemisorption of CO2. We demonstrate the presence of an additional configurational energy barrier for nanometer‐sized vacancies resulting in a significantly slower rate of expansion. Finally, CO2 etching is applied to map the location of the intrinsic vacancies in the polycrystalline graphene film where we show that the intrinsic vacancy defects manifest mainly as grain boundary defects where intragrain defects from oxidative etching constitute a minor population. [ABSTRACT FROM AUTHOR]

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We report on the reversible uptake of carbon dioxide by dimetallynes featuring ancillary hemi‐labile pincer ligands. Insertion into the Ge−Ge/Sn−Sn bonds yields species containing an E(CO2)E unit, with the mode of ligation of the CO2 fragment determined crystallographically being found to be dependent on the identity of the Group 14 element. The thermodynamics of CO2 uptake/loss can be established through VT NMR (ΔH°=+24.6(2.3) kJ mol−1, ΔS°=+64.9(3.8) J mol−1 K−1, ΔG°298=+5.3(1.9) kJ mol−1 for the loss of CO2 in the Ge case), and the chemical consequences of reversibility demonstrated by thermodynamically‐controlled exchange reactions. [ABSTRACT FROM AUTHOR]

Green carbon science is defined as the "study and optimization of the transformation of carbon‐containing compounds and the relevant processes involved in the entire carbon cycle from carbon resource processing, carbon energy utilization, CO2 fixation, and carbon recycling to utilize carbon resources efficiently and minimize the net CO2 emission."[1] Green carbon science is related closely to carbon neutrality, and relevant fields have developed quickly in the last decade. In this Minireview, we propose the concept of carbon energy index, and the recent progress in petroleum refining, and the production of liquid fuels, chemicals, and materials using coal, methane, CO2, biomass, and waste plastics is highlighted in combination with green carbon science. An outlook for these important fields is provided in the final section. [ABSTRACT FROM AUTHOR]

Carbon dioxide, metal-organic frameworks, methanation, photothermal catalysis, pyrolysis Frontispiz: An Efficient Metal-Organic Framework-Derived Nickel Catalyst for the Light Driven Methanation of CO2 Keywords: carbon dioxide; metal-organic frameworks; methanation; photothermal catalysis; pyrolysis EN carbon dioxide metal-organic frameworks methanation photothermal catalysis pyrolysis 1 1 1 12/09/21 20211213 NES 211213 B Heterogene Katalyse b In der Zuschrift auf S. 26680 berichten Luis Garzón-Tovar, Jorge Gascon et al. über einen aus einer metall-organischen Gerüstverbindung hergestellten Nickelkatalysator für die photochemische Methanierung von CO SB 2 sb . [Extracted from the article]