Synthesis of higher carboxylic acids from ethers, CO2 and H2

Electrochemical Synthesis of Itaconic Acid Derivatives via Chemodivergent Single and Double Carboxylation of Allenes with CO2

Leveraging electrochemistry, a new synthesis of non-natural derivatives of itaconic acid is proposed by utilizing carbon dioxide (CO2) as a valuable C1 synthon. An electrochemical cross-electrophile coupling between allenoates and CO2 was targeted, allowing for the synthesis of both mono- and di-carboxylation products in a catalyst- and additive-free environment (yields up to 87 %, 30 examples). Elaboration of the model mono-carboxylation product, and detailed cyclovoltammetric, as well as mechanistic analyses complete the present investigation.

Synergistic effects of core-shell poly(ionic liquids)@ZIF-8 nanocomposites for enhancing additive-free CO2 conversion

The present study, for the first time, reports the fabrication of core-shell poly(ionic liquids)@ZIF-8 nanocomposites through a facile in-situ polymerization strategy. These composites exhibited exceptional structural characteristics including high specific surface areas and the integration of high-density Lewis acid/base and nucleophilic active sites. The structure-activity relationship, reusability, and versatility of the poly(ionic liquids)@ZIF-8 composites were investigated for the cycloaddition reaction between CO2 and epoxide. By optimizing the composites structures and their catalytic performance, PIL-Br@ZIF-8(2:1) was identified as an exciting catalyst that exhibits high activity and selectivity in the synthesis of various cyclic carbonates under mild or even atmospheric pressure or simulated flue gas conditions. Moreover, the catalyst demonstrated excellent structural stability while maintaining its catalytic activity throughout multiple usage cycles. By combining DFT calculations, we investigated the transition states and intermediate geometries of the cycloaddition reaction in different coordination microenvironments, thereby proposing a synergistic catalytic mechanism involving multiple active sites.

Formic acid stability in different solvents by DFT calculations

CONTEXT

New technologies have been developed toward the use of green energies. The production of formic acid (FA) from carbon dioxide (CO[Formula: see text]) hydrogenation with H[Formula: see text] is a sustainable process for H[Formula: see text] storage. However, the FA adduct stabilization is thermodynamically dependent on the type of solvent and thermodynamic conditions. The results suggest a wide range of dielectric permittivity values between the dimethyl sulfoxide (DMSO) and water solvents to stabilize the FA in the absence of base. The thermodynamics analysis and the infrared and charge density difference results show that the formation of the FA complex with H[Formula: see text]O is temperature dependent and has a major influence on aqueous solvents compared to the FA adduct with amine, in good agreement with the experiment. In these conditions, the stability thermodynamic of the FA molecule may be favorable at non-organic solvents and dielectric permittivity values closer to water. Therefore, a mixture of aqueous solvents with possible ionic composition could be used to increase the thermodynamic stability of H[Formula: see text] storage in CO[Formula: see text] conversion processes.

METHODS

Using the Quantum ESPRESSO package, density functional theory (DFT) calculations were performed with periodic boundary conditions, and the electronic wave functions were expanded in plane waves. For the exchange-correlation functional, we use the vdW-DF functional with the inclusion of van der Waals (vdW) forces. Electron-ion interactions are treated by the projector augmented wave (PAW) method with pseudopotentials available in the PSlibrary repository. The wave functions and the electronic densities were expanded employing accurate cut-off energies of 6.80[Formula: see text]10[Formula: see text] and 5.44[Formula: see text]10[Formula: see text] eV, respectively. The electronic density was computed from the wave functions calculated at the [Formula: see text]-point in the first Brillouin-zone. Each structural optimization was minimized according to the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm, with force and energy convergence criteria of 25 meV[Formula: see text]Å[Formula: see text] and 1.36 meV, respectively. The electrostatic solvation effects were performed by the [Formula: see text] package with the Self-Consistent Continuum Solvation (SCCS) approach.

Promoting nonsymmetric C-C coupling to valuable oxygenates without metal catalysts in alkali aqueous medium

Efficient conversion of C1 molecules into multicarbon oxygenates is a promising avenue for energy storage. Herein, we synthesize adjustable alkanoic acids/alcohols from formate C1 molecules via a hydrothermal reaction without any metal catalyst participation. This is achieved via HCO* and HCOO- nonsymmetric C-C coupling by alkali catalysis in aqueous medium.

Transformation of CO2 and H2 to C2+ chemicals and fuels

This perspective highlights the progress of CO2 hydrogenation to multicarbon (C2+) products, by discussing some typical related works, future opportunities and challenges.

Evaluation of CO2 and H2O Adsorption on a Porous Polymer Using DFT and In Situ DRIFT Spectroscopy

Numerous hyper-cross-linked polymers (HCPs) have been developed as CO₂ adsorbents and photocatalysts. Yet, little is known of the CO₂ and H₂O adsorption mechanisms on amorphous porous polymers. Gaining a better understanding of these mechanisms and determining the adsorption sites are key to the rational design of improved adsorbents and photocatalysts. Herein, we present a unique approach that combines density functional theory (DFT), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and multivariate spectral analysis to investigate CO₂ and H₂O adsorption sites on a triazine-biphenyl HCP. We found that CO₂ and H₂O adsorb on the same HCP sites albeit with different adsorption strengths. The primary amines of the triazines were identified as favoring strong CO₂ binding interactions. Given the potential use of HCPs for CO₂ photoreduction, we also investigated CO₂ and H₂O adsorption under transient light irradiation. Under irradiation, we observed partial CO₂ and H₂O desorption and a redistribution of interactions between the H₂O and CO₂ molecules that remain adsorbed at HCP adsorption sites.

Vertical Conductivity and Topography in Electrostrictive Germanium Sulfide Microribbon via Conductive Atomic Force Microscopy

Layered group IV monochalcogenides are two-dimensional (2D) semiconducting materials with unique crystal structures and novel physical properties. Here, we report the growth of single crystalline GeS microribbons using the chemical vapor transport process. By using conductive atomic force microscopy, we demonstrated that the conductive behavior in the vertical direction was mainly affected by the Schottky barriers between GeS and both electrodes. Furthermore, we found that the topographic and current heterogeneities were significantly different with and without illumination. The topographic deformation and current enhancement were also predicted by our density functional theory (DFT)-based calculations. Their local spatial correlation between the topographic height and current was established. By virtue of 2D fast Fourier transform power spectra, we constructed the holistic spatial correlation between the topographic and current heterogeneity that indicated the diminished correlation with illumination. These findings on layered GeS microribbons provide insights into the conductive and topographic behaviors in 2D materials.

Design and Analysis of Metal Oxides for CO2 Reduction Using Machine Learning, Transfer Learning, and Bayesian Optimization

We aim to achieve resource recycling by capturing and using CO₂ generated in a chemical production and disposal process. We focused on CO₂ conversion to CO by the reverse water gas shift-chemical looping (RWGS-CL) reaction. This reaction proceeds in two steps (H₂ + MO _x ⇆ H₂O + MO _x-1; CO₂ + MO _x-1 ⇆ CO + MO _x ) via a metal oxide that acts as an oxygen carrier. High CO₂ conversion can be achieved owing to a low H₂O concentration in the second step, which causes an unwanted back reaction (H₂ + CO₂ ⇆ CO + H₂O). However, the RWGS-CL process is difficult to control because of repeated thermochemical redox cycling, and the CO₂ and H₂ conversion extents vary depending on the metal oxide composition and experimental conditions. In this study, we developed metal oxides and simultaneously optimized experimental conditions to satisfy target CO₂ and H₂ conversion extents by using machine learning and Bayesian optimization. We used transfer learning to improve the prediction accuracy of the mathematical models by incorporating a data set and knowledge of oxygen vacancy formation energy. Furthermore, we analyzed the RWGS-CL reaction based on the prediction accuracy of each variable and the feature importance of the random forest regression model.

Green Carbon Science: Efficient Carbon Resource Processing, Utilization, and Recycling Towards Carbon Neutrality

Green carbon science is defined as "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, and carbon recycling to use carbon resources efficiently and minimize the net CO2 emission." [1] Green carbon science is related closely to carbon neutrality, and the relevant fields have developed quickly in the last decade. In this Minireview, we proposed the concept of carbon energy index, and the recent progresses in petroleum refining, production of liquid fuels, chemicals, and materials using coal, methane, CO2, biomass, and waste plastics are highlighted in combination with green carbon science, and an outlook for these important fields is provided in the final section.

Synthesis of C2+ Chemicals from CO2 and H2 via C-C Bond Formation

ConspectusThe severity of global warming necessitates urgent CO₂ mitigation strategies. Notably, CO₂ is a cheap, abundant, and renewable carbon resource, and its chemical transformation has attracted great attention from society. Because CO₂ is in the highest oxidation state of the C atom, the hydrogenation of CO₂ is the basic means of converting it to organic chemicals. With the rapid development of H₂ generation by water splitting using electricity from renewable resources, reactions using CO₂ and H₂ have become increasingly important. In the past few decades, the advances of CO₂ hydrogenation have mostly been focused on the synthesis of C1 products, such as CO, formic acid and its derivatives, methanol, and methane. In many cases, the chemicals with two or more carbons (C₂₊) are more important. However, the synthesis of C₂₊ chemicals from CO₂ and H₂ is much more difficult because it involves controlled hydrogenation and simultaneous C-C bond formation. Obviously, investigations on this topic are of great scientific and practical significance. In recent years, we have been targeting this issue and have successfully synthesized the basic C₂₊ chemicals including carboxylic acids, alcohols, and liquid hydrocarbons, during which we discovered several important new reactions and new reaction pathways. In this Account, we systematically present our work and insights in a broad context with other related reports.1.We discovered a reaction of acetic acid production from methanol, CO₂ and H₂, which is different from the well-known methanol carbonylation. We also discovered a reaction of C₃₊ carboxylic acids syntheses using ethers to react with CO₂ and H₂, which proceeds via olefins as intermediates. Following the new reaction, we realized the synthesis of acetamide by introducing various amines, which may inspire the development of further catalytic schemes for preparing a variety of special chemicals using carbon dioxide as a building block.2.We designed a series of homogeneous catalysts to accelerate the production of C₂₊ alcohols via CO₂ hydrogenation. In the heterogeneously catalyzed CO₂ hydrogenation, we discovered the role of water in enhancing the synthesis of C₂₊ alcohols. We also developed a series of routes for ethanol production using CO₂ and H₂ to react with some substrates, such as methanol, dimethyl ether, aryl methyl ether, lignin, or paraformaldehyde.3.We designed a catalyst that can directly hydrogenate CO₂ to C₅₊ hydrocarbons at 200 °C, not via the traditional CO or methanol intermediates. We also designed a route to couple homogeneous and heterogeneous catalysis, where exceptional results are achieved at 180 °C.

Low temperature methanation of CO2 over an amorphous cobalt-based catalyst

CO2 methanation is an important reaction in CO2 valorization. Because of the high kinetic barriers, the reaction usually needs to proceed at higher temperature (>300 °C). High-efficiency CO2 methanation at low temperature (<200 °C) is an interesting topic, and only several noble metal catalysts were reported to achieve this goal. Currently, design of cheap metal catalysts that can effectively accelerate this reaction at low temperature is still a challenge. In this work, we found that the amorphous Co-Zr0.1-B-O catalyst could catalyze the reaction at above 140 °C. The activity of the catalyst at 180 °C reached 10.7 mmolCO2 gcat -1 h-1, which is comparable to or even higher than that of some noble metal catalysts under similar conditions. The Zr promoter in this work had the highest promoting factor to date among the catalysts for CO2 methanation. As far as we know, this is the first report of an amorphous transition metal catalyst that could effectively accelerate CO2 methanation. The outstanding performance of the catalyst could be ascribed to two aspects. The amorphous nature of the catalyst offered abundant surface defects and intrinsic active sites. On the other hand, the Zr promoter could enlarge the surface area of the catalyst, enrich the Co atoms on the catalyst surface, and tune the valence state of the atoms at the catalyst surface. The reaction mechanism was proposed based on the control experiments.

Photocatalytic Reduction of CO2 to CO over Quinacridone/BiVO4 Nanocomposites

Solar energy-driven photoreduction of CO₂ to energy-rich chemicals is of significance for sustainable development but challenging. Herein, quinacridone (QA)/nBiVO₄ (n=0.2-20, in which n stands for the mass ratio of BiVO₄ to QA) nanocomposites were developed for photoreduction of CO₂ . Characterization of the materials with Fourier-transform (FT)IR spectroscopy and X-ray photoelectron spectroscopy (XPS) pointed to QA/nBiVO₄ preparation via hydrogen-bonding-directed self-assembly of QA on BiVO₄ nanosheets. Using triethanolamine (TEOA) as a sacrifice reagent, QA/10BiVO₄ showed the best performance, affording CO with a production rate of 407 μmol g^-1  h^-1 , 24 times higher than those of pure QA. It was indicated that the Z-scheme charge-transfer mechanism of QA/nBiVO₄ could significantly improve the separation and transmission efficiency of photo-generated electrons and holes. This novel approach provides new insight for fabricating the composite photocatalytic materials of small molecule organic semiconductors and inorganic semiconductors with high efficiency for photocatalytic of reduction CO₂ .

Deoxygenative α-alkylation and α-arylation of 1,2-dicarbonyls

Construction of C-C bonds at the α-carbon is a challenging but synthetically indispensable approach to α-branched carbonyl motifs that are widely represented among drugs, natural products, and synthetic intermediates. Here, we describe a simple approach to generation of boron enolates in the absence of strong bases that allows for introduction of both α-alkyl and α-aryl groups in a reaction of readily accessible 1,2-dicarbonyls and organoboranes. Obviation of unselective, strongly basic and nucleophilic reagents permits carrying out the reaction in the presence of electrophiles that intercept the intermediate boron enolates, resulting in two new α-C-C bonds in a tricomponent process.