CO2 Utilization Strategy Research Articles

Heteroatom‐Containing Zeolites as Solid Lewis Acid Catalysts for the Cycloaddition of CO2 to Epoxides

AbstractThe catalytic cycloaddition of CO2 to epoxides to produce valuable cyclic carbonates represents a simple and promising strategy for CO2 utilization, circumventing the ineffective CO2 reduction process. Despite current progresses, there remains an impending demand for highly‐active, cost‐effective and stable catalysts especially the ideal heterogeneous catalytic systems. Herein, we report the preparation of heteroatom‐containing zeolites through a two‐step process comprising of framework dealumination and subsequent heteroatom incorporation, and their catalytic applications in CO2 cycloaddition to epoxides. Characterization results reveal the successful incorporation of heteroatoms into framework to derive Lewis acidic M‐Beta zeolites (M = Ti, Zr or Hf). The as‐prepared M‐Beta Lewis acids show remarkable performance in the model reaction of CO2 cycloaddition to propylene oxide with the assistance of potassium iodide under solvent‐free conditions. The reaction parameters have been optimized employing Ti‐Beta catalyst and the substrate scope has been investigated. Finally, the impact of Lewis acidity on the cycloaddition reaction is discussed and the actual bifunctional Ti‐Beta/KI catalyst system is proposed, which is of important significance for the understanding of CO2 catalytic cycloaddition to epoxides.

Spatially explicit supply chain for nationwide CO2-to-fuel infrastructure: Data-driven optimization with Gaussian mixture model -based region screening and clustering

This study proposes a novel machine learning-based method for designing spatially explicit supply chains for establishing a nationwide CO2 utilization strategy. The proposed method is capable of considering not only technical feature for CO2-to-fuel conversion, but also the geographical features for facility allocation by integrating spatial data and various sociological information. To develop the proposed method, map polygonization and the ray-casting algorithm for precise spatial data generation are implemented, which identifies and screens out geographically and socially unfavorable terrains for facility allocation. The scenario evaluation method, which includes the Gaussian mixture model-based expectation–maximization algorithm and supply chain economics, such as transportation price and facility capital investment, are considered to calculate a large set of supply chain scenarios. As a case study, the proposed method is applied to determine the optimal supply chain configuration to secure economic feasibility in the Korean CO2 capture and utilization project. The results identify the hydrogen price as the most critical factor in the supply chain economy and show the potential profitability in 2043–2045. This study can promote the nationwide CO2 reduction strategy and the development of a sustainable energy supply system.

CO2-Based Stable Porous Metal-Organic Frameworks for CO2 Utilization.

The transformation of carbon dioxide (CO2) into functional materials has garnered considerable worldwide interest. Metal-organic frameworks (MOFs), as a distinctive class of materials, have made great contributions to CO2 capture and conversion. However, facile conversion of CO2 to stable porous MOFs for CO2 utilization remains unexplored. Herein, we present a facile methodology of using CO2 to synthesize stable zirconium-based MOFs. Two zirconium-based MOFs CO2-Zr-DEP and CO2-Zr-DEDP with face-centered cubic topology were obtained via a sequential desilylation-carboxylation-coordination reaction. The MOFs exhibit excellent crystallinity, as verified through powder X-ray diffraction and high-resolution transmission electron microscopy analyses. They also have notable porosity with high surface area (SBET up to 3688 m2 g-1) and good CO2 adsorption capacity (up to 12.5 wt %). The resulting MOFs have abundant alkyne functional moieties, confirmed through 13C cross-polarization/magic angle spinning nuclear magnetic resonance and Fourier transform infrared spectra. Leveraging the catalytic prowess of Ag(I) in diverse CO2-involved reactions, we incorporated Ag(I) into zirconium-based MOFs, capitalizing on their interactions with carbon-carbon π-bonds of alkynes, thereby forming a heterogeneous catalyst. This catalyst demonstrates outstanding efficiency in catalyzing the conversion of CO2 and propargylic alcohols into cyclic carbonates, achieving >99% yield at room temperature and atmospheric pressure conditions. Thus, this work provides a dual CO2 utilization strategy, encompassing the synthesis of CO2-based MOFs (20-24 wt % from CO2) and their subsequent application in CO2 capture and conversion processes. This approach significantly enhances overall CO2 utilization.

High-performance and selective catalyst for the chemical fixation of CO2 into cyclic carbonates based on pyridinium-based deep eutectic solvent

Rising atmospheric CO2 levels have prompted interest in chemical fixation routes to convert CO2 into value-added cyclic carbonates. This study reports a high-performance catalyst based on a pyridinium-based deep eutectic solvent (DES) for CO2 cycloaddition with epoxides under mild conditions. The DES was prepared by mixing 1-(carboxymethyl)pyridinium bromide ([CMPy]Br) as a hydrogen bond acceptor with maleic acid as an inexpensive and eco-friendly hydrogen bond donor [HBD]. The melting point depression enables the DES to act as a homogeneous catalyst without additional solvents. A diverse range of cyclic carbonates were synthesized in high yields from various epoxides and CO2 under atmospheric pressure at 90–110 °C temperatures. Compared to other catalytic systems, the offered DES significantly reduced reaction times of 1–3 h to achieve best quantitative conversions. The DES was recyclable for at least 5 runs without loss of activity. The high performance was attributed to the DES' ability to activate epoxides via hydrogen bonding while stabilizing reaction intermediates. This metal-free and solvent-free approach provides an efficient strategy for CO2 utilization under green conditions using readily available pyridinium-based DES.

An Overview of Metal-organic Framework Based Electrocatalysts: Design and Synthesis for Electrochemical Hydrogen Evolution, Oxygen Evolution, and Carbon Dioxide Reduction Reactions.

Due to the increasing global energy demands, scarce fossil fuel supplies, and environmental issues, the pursued goals of energy technologies are being sustainable, more efficient, accessible, and produce near zero greenhouse gas emissions. Electrochemical water splitting is considered as a highly viable and eco-friendly energy technology. Further, electrochemical carbon dioxide (CO2 ) reduction reaction (CO2 RR) is a cleaner strategy for CO2 utilization and conversion to stable energy (fuels). One of the critical issues in these cleaner technologies is the development of efficient and economical electrocatalyst. Among various materials, metal-organic frameworks (MOFs) are becoming increasingly popular because of their structural tunability, such as pre- and post- synthetic modifications, flexibility in ligand design and its functional groups, and incorporation of different metal nodes, that allows for the design of suitable MOFs with desired quality required for each process. In this review, the design of MOF was discussed for specific process together with different synthetic methods and their effects on the MOF properties. The MOFs as electrocatalysts were highlighted with their performances from the aspects of hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and electrochemical CO2 RR. Finally, the challenges and opportunities in this field are discussed.

Unlocking high carbonation efficiency: Direct CO2 mineralization with fly ash and seawater

Direct CO2 mineralization using fly ash is a promising technology to achieve CO2 sequestration. Seawater's abundance and calcium-rich composition make it an attractive substitute solution for CO2 sequestration. However, there have been limited studies conducted so far, and the mineralization mechanism remains unclear, which has constrained its industrial application potential. Here we utilized low CaO-content fly ash in combination with seawater to perform direct CO2 mineralization under ambient conditions, achieving a remarkable carbonation efficiency of 94.8 %. Upon scrutinizing the carbonate parameter evolution, we identify a crucial pH range (8.2 ∼ 10.4) that enhances calcium elution efficiency, leading to heightened carbonation efficiency. The involvement of Mg(OH)2 within this pH range influences CaCO3 precipitation kinetics and crystalline phase. This innovative approach holds promise for carbon sequestration and presents a valuable contribution to sustainable CO2 utilization strategies.

Ni12P5 Confined in Mesoporous SiO2 with Near-Unity CO Selectivity and Enhanced Catalytic Activity for CO2 Hydrogenation.

CO2 hydrogenation via the reverse water gas shift (RWGS) reaction is a promising strategy for CO2 utilization while constructing Ni-based catalysts with high catalytic activity and perfect CO selectivity remains a great challenging. Here, we demonstrate that the product selectivity for CO2 hydrogenation can be significantly tuned from CH4 to CO by phosphating of SiO2-supported Ni catalysts due to the geometric effect. Interestingly, nickel phosphide catalysts with different crystalline phases (Ni12P5 and Ni2P) differ sharply in CO2 conversion, and Ni12P5 is remarkably more active. Furthermore, we developed a facile strategy to confine small Ni12P5 nanoparticles in mesoporous SiO2 channels (Ni12P5@SBA-15). Enhanced activity is exhibited on Ni12P5@SBA-15, ascribed to the highly effective confinement effect. The in situ diffuse reflectance infrared Fourier transform spectroscopy and density functional theory calculations unveil that catalytic CO2 hydrogenation follows a direct CO2 dissociation route with adsorbed CO as the key intermediate. Notably, strong multibonded CO (threefold and bridge-bonded CO) is feasibly formed on the Ni catalyst accounting for CH4 as the dominant product whereas only weak linearly bonded CO exists on nickel phosphide catalysts resulting in almost 100% CO selectivity. The present results indicate that Ni12P5@SBA-15 combining the geometric effect and the confinement effect can achieve near-unity CO selectivity and enhanced activity for CO2 hydrogenation.

Correlating Metal Redox Potentials to Co(III)K(I) Catalyst Performances in Carbon Dioxide and Propene Oxide Ring Opening Copolymerization

AbstractCarbon dioxide copolymerization is a front‐runner CO2 utilization strategy but its viability depends on improving the catalysis. So far, catalyst structure‐performance correlations have not been straightforward, limiting the ability to predict how to improve both catalytic activity and selectivity. Here, a simple measure of a catalyst ground‐state parameter, metal reduction potential, directly correlates with both polymerization activity and selectivity. It is applied to compare performances of 6 new heterodinuclear Co(III)K(I) catalysts for propene oxide (PO)/CO2 ring opening copolymerization (ROCOP) producing poly(propene carbonate) (PPC). The best catalyst shows an excellent turnover frequency of 389 h−1 and high PPC selectivity of >99 % (50 °C, 20 bar, 0.025 mol% catalyst). As demonstration of its utility, neither DFT calculations nor ligand Hammett parameter analyses are viable predictors. It is proposed that the cobalt redox potential informs upon the active site electron density with a more electron rich cobalt centre showing better performances. The method may be widely applicable and is recommended to guide future catalyst discovery for other (co)polymerizations and carbon dioxide utilizations.

Correlating Metal Redox Potentials to Co(III)K(I) Catalyst Performances in Carbon Dioxide and Propene Oxide Ring Opening Copolymerization.

Carbon dioxide copolymerization is a front-runner CO2 utilization strategy but its viability depends on improving the catalysis. So far, catalyst structure-performance correlations have not been straightforward, limiting the ability to predict how to improve both catalytic activity and selectivity. Here, a simple measure of a catalyst ground-state parameter, metal reduction potential, directly correlates with both polymerization activity and selectivity. It is applied to compare performances of 6 new heterodinuclear Co(III)K(I) catalysts for propene oxide (PO)/CO2 ring opening copolymerization (ROCOP) producing poly(propene carbonate) (PPC). The best catalyst shows an excellent turnover frequency of 389 h-1 and high PPC selectivity of >99 % (50 °C, 20 bar, 0.025 mol% catalyst). As demonstration of its utility, neither DFT calculations nor ligand Hammett parameter analyses are viable predictors. It is proposed that the cobalt redox potential informs upon the active site electron density with a more electron rich cobalt centre showing better performances. The method may be widely applicable and is recommended to guide future catalyst discovery for other (co)polymerizations and carbon dioxide utilizations.

Facilitating electroreduction CO2-to-C2H4 over doped CuO nanospheres assisted by nitrogen species and oxygen vacancies

Electrocatalytic reduction is a promising strategy for CO2 utilization, while the conversion of CO2 to C2 products usually suffers from the low selectivity. Herein, we report several high-performance Cu-OCN catalysts for electroreduction CO2-to-C2H4, which are prepared through the in-situ calcination of nanocube Cu2O and urea. The highest C2H4 faradaic efficiency from Cu-OCN-10 reaches 55.97%, much higher than that from the pristine CuO counterpart (38.31%), with a partial current density of −12.83 mA cm−2. Catalyst characterizations and first-principles density functional theory calculations reveal that the superior performance of CuO-OCN is attributed to the introduced nitrogen (N) species and oxygen (O)-vacancies. With the assistance of N species and O-vacancies, the adsorption of CO2 on Cu-OCN-10 is thermodynamically favorable with the absorption energy of −0.69 eV. Meanwhile, the activation of CO2 is promoted and the generated *CO intermediate on Cu-OCN-10 is stable, whose release needs to overcome an energy of 2.26 eV, thereby enhancing the CC coupling to produce C2H4. In general, the synergistic effects of N species and O-vacancies in Cu-OCN catalysts facilitate CO2 electroreduction to C2H4.

Potential reversible reactions over PdNix alloy catalysts: Hydrogen evolution from formic acid and formic acid formation by CO2 reduction reaction

A novel approach is required to achieve effective CO2 utilization. This study demonstrates a new approach for the reversible reaction in the CO2-HCOOH cycle, that is, FA decomposition and CO2 reduction, under ambient pressure using Pd-based alloy catalysts. First, Pd-based alloys (Pd-M; M = Co, Ni, and Zn) were screened for FA decomposition; the PdNi alloy showed superior catalytic activity compared to Pd and the other alloys. Second, Pd3Ni, PdNi, and PdNi3 were prepared to understand the composition-dependent activity of the PdNix series. DFT calculations provided insight into why the PdNix alloys show higher catalytic activities for FA decomposition than Pd. Finally, the electrochemical CO2 reduction reaction was investigated, and the PdNix alloy catalysts showed superior selectivity for FA formation compared to Pd catalysts. Thus, this study provides a novel strategy for CO2 utilization using bimetallic Pd-Ni heterogeneous catalysts.

A Review on the Progress in Chemo-Enzymatic Processes for CO2 Conversion and Upcycling

The increasing concentration of atmospheric CO2 due to human activities has resulted in serious environmental issues such as global warming and calls for efficient ways to reduce CO2 from the environment. The conversion of CO2 into value-added compounds such as methane, formic acid, and methanol has emerged as a promising strategy for CO2 utilization. Among the different techniques, the enzymatic approach based on the CO2 metabolic process in cells presents a powerful and eco-friendly method for effective CO2 conversion and upcycling. This review discusses the catalytic conversion of CO2 using single and multienzyme systems, followed by various chemo-enzymatic processes to produce bicarbonates, bulk chemicals, synthetic organic fuel and synthetic polymer. We also highlight the challenges and prospects for future progress in CO2 conversion via chemo-enzymatic processes for a sustainable solution to reduce the global carbon footprint.

Optimized manufacturing of gas diffusion electrodes for CO2 electroreduction with automatic spray pyrolysis

Despite being one of the most promising CO2 utilization strategies some aspects still hinder the scaling up of CO2 electroreduction processes. One of them is the fabrication of the electrodes, which is currently rudimentary and depends fundamentally on the human factor. Here, we report an automated spray pyrolysis technique coupled with a plasma surface treatment to fabricate Bi-based gas diffusion electrodes for a enhanced CO2 electroreduction to formate. Three fabrication parameters, namely i) spraying nozzle height, ii) step distance, and iii) ink flow rate, are evaluated to determine the optimal fabrication conditions. The results confirm the reproducibility of the fabrication method, improving the overall performance of the electrodes fabricated with a manual airbrushing method, and leading to formate rates of up to 10.1 mmol m−2 s−1 at 200 mA cm−2. Besides, plasma treatment can improve formate concentration by up to 12 % in comparison with the untreated electrode. As a result, this work provides novel insights into the development of more efficient methods to manufacture electrodes for CO2 electroreduction, which will eventually bring this technology closer to an industrial scale.

Metal-Free Amine-Anchored Triazine-Based Covalent Organic Polymers for Selective CO2 Adsorption and Conversion to Cyclic Carbonates Under Mild Conditions

Attaining both large uptake and high conversion of CO2 under mild reaction conditions within a metal-free covalent organic polymer (COP) is an attractive and challenging strategy for CO2 utilization because CO2 is an abundant and renewable C1 source and a main greenhouse gas. In this study, novel amine-anchored covalent triazine aromatic polymers (CTP-1-NH2 and CTP-2-NH2) were synthesized from 2-amino-4,6-dichloro-1,3,5-triazine, biphenyl, and 1,3,5-triphenylbenzene via facile Friedel–Crafts arylation for CO2 adsorption and conversion reaction. At 273 K and 1 bar, CTP-1-NH2 and CTP-2-NH2 exhibited CO2 uptakes of 187.4 and 224.41 mg/g and CO2/N2 selectivity of 69.45 and 61.38, respectively, outperforming many previously reported COP materials. Moreover, metal-free CTP-1-NH2 with tetrabutylammonium bromide (n-Bu4NBr) exhibited high epoxide conversion and product selectivity under mild (40 °C and 1 bar) and solvent-free conditions within 36 h of reaction time, which were very much comparable to the performances of many metal-coordinated COP catalysts. The spent catalyst was also highly reusable with no active species leaching. A plausible mechanism for CO2 cycloaddition over the CTP-1-NH2 catalyst is proposed. Incorporating amine functionalities into a nitrogen-rich structure could be a promising strategy for developing materials with simultaneous CO2 capture and conversion.

Superstructure optimization model for design and analysis of CO2-to-fuels strategies

CO2 utilization to fuel production, wherein captured CO2 is used as raw materials and partially replaces the use of fossil fuels, is an effective solution for energy security and global warming. In this study, an optimization-based framework was developed for CO2-to-fuel superstructure to determine the optimal strategies for desired fuels (i.e., methanol (MeOH), Fischer–Tropsch synthesis (FT) fuels, dimethyl ether (DME), and gasoline). The aim of the framework is to address specific problems of minimizing energy consumption, unit production cost, and net CO2 equivalent emission. Thus, we first generated a superstructure of alternative CO2-to-fuel pathways, and each pathway contains a set of carbon conversion and separation technologies toward the final fuel from CO2 feedstock. Subsequently, a process simulation and energy–economic–environmental parameters of possible pathways were generated and further embedded into the optimization model. The optimization results indicate that, among CO2 utilization technologies, direct catalytic hydrogenation is recognized as the most economical and environmentally friendly pathway for MeOH at 3.6 $/GGE (reduced 1.01 kg CO2/GGE), gasoline at 3.71 $/GGE (reduced 1.86 kg CO2/GGE), and DME at 4.46 $/GGE and near-zero-emission. However, FT fuels are not suggested since they consume more energy for a higher production cost and emit 3.22 kg CO2/GGE. Using various process system engineering-centric techniques, this study also determined that H2 feedstock cost, associated with CO2 utilization strategies, is the major economic–environmental factor and investigated the CO2-to-fuel application potential in various market conditions based on regions or time.

Efficiency in CO2-utilization strategies: The case of styrene carbonate synthesis in microdroplets conditions

The styrene oxide to styrene carbonate conversion performed in CO2 atmosphere, herein selected as a case study, was implemented in microdroplets (aerosol) reactions at the preparative scale (3.5 mmol of the starting material) and mild conditions (1 atm CO2 pressure), within a custom-made ultrasonic nebulization reactor. Upon optimization of the promoter stoichiometry (1 eq of 4.3 TEG/KI ratio) and methanol (MeOH) dilution (7.5 mL of 2.5 v/v MeOH/TEG), performances under mass transfer-limited conditions of this novel methodological paradigm have been compared at 25 °C and 50 °C with those implemented as: a) no-stirred, b) stirred, and c) sonicated bulk reactions. Complete selectivity and an apparent acceleration factor (AAF) of 1.9 was registered at both temperature for microdroplets reactions in respect with the sonicated counterparts, these latter performing better than the other bulk reactions. These significative efficiency improvements, candidate aerosol reactions as a preferred process intensification approach in the realm of effective CO2-utilization strategies and, in general, in the development and exploitation of gas-liquid two-phase reactions.

Design of Full-Temperature-Range RWGS Catalysts: Impact of Alkali Promoters on Ni/CeO2.

Reverse water gas shift (RWGS) competes with methanation as a direct pathway in the CO2 recycling route, with methanation being a dominant process in the low-temperature window and RWGS at higher temperatures. This work showcases the design of multi-component catalysts for a full-temperature-range RWGS behavior by suppressing the methanation reaction at low temperatures. The addition of alkali promoters (Na, K, and Cs) to the reference Ni/CeO2 catalyst allows identifying a clear trend in RWGS activation promotion in both low- and high-temperature ranges. Our characterization data evidence changes in the electronic, structural, and textural properties of the reference catalyst when promoted with selected dopants. Such modifications are crucial to displaying an advanced RWGS performance. Among the studied promoters, Cs leads to a more substantial impact on the catalytic activity. Beyond the improved CO selectivity, our best performing catalyst maintains high conversion levels for long-term runs in cyclable temperature ranges, showcasing the versatility of this catalyst for different operating conditions. All in all, this work provides an illustrative example of the impact of promoters on fine-tuning the selectivity of a CO2 conversion process, opening new opportunities for CO2 utilization strategies enabled by multi-component catalysts.

Densely packed ultrafine SnO2 nanoparticles grown on carbon cloth for selective CO2 reduction to formate

Electrochemical reduction of CO2 to fuels and chemicals is a viable strategy for CO2 utilization and renewable energy storage. Developing free-standing electrodes from robust and scalable electrocatalysts becomes highly desirable. Here, dense SnO2 nanoparticles are uniformly grown on three-dimensional (3D) fiber network of carbon cloth (CC) by a facile dip-coating and calcination method. Importantly, Zn modification strategy is employed to restrain the growth of long-range order of SnO2 lattices and to produce rich grain boundaries. The hybrid architecture can act as a flexible electrode for CO2-to-formate conversion, which delivers a high partial current of 18.8 mA cm−2 with a formate selectivity of 80% at a moderate cathodic potential of −0.947 V vs. RHE. The electrode exhibits remarkable stability over a 16 h continuous operation. The superior performance is attributed to the synergistic effect of ultrafine SnO2 nanoparticles with abundant active sites and 3D fiber network of the electrode for efficient mass transport and electron transfer. The sizeable electrodes hold promise for industrial applications.

Newly explored formate dehydrogenases from Clostridium species catalyze carbon dioxide to formate

With concerns over global warming and climate change, many efforts have been devoted to mitigate atmospheric CO2 level. As a CO2 utilization strategy, formate dehydrogenase (FDH) from Clostridium species were explored to discover O2-tolerant and efficient FDHs that can catalyze CO2 to formate (i.e. CO2 reductase). With FDH from Clostridium ljungdahlii (ClFDH) that plays as a CO2 reductase previously reported as the reference, FDH from C.autoethanogenum (CaFDH), C. coskatii (CcFDH), and C. ragsdalei (CrFDH) were newly discovered via genome-mining. The FDHs were expressed in Escherichia coli and the recombinant FDHs successfully catalyzed CO2 reduction with a specific activity of 15 U g−1-CaFDH, 17 U g−1-CcFDH, and 8.7 U g−1-CrFDH. Interestingly, all FDHs newly discovered retain their catalytic activity under aerobic condition, although Clostridium species are strict anaerobe. The results discussed herein can contribute to biocatalytic CO2 utilization.

Recombinant expression and characterization of formate dehydrogenase from Clostridium ljungdahlii (ClFDH) as CO2 reductase for converting CO2 to formate

Recent concerns over climate change have triggered many efforts to mitigate atmospheric CO2 levels. Among the CO2 utilization strategies, we, herein, aimed to biochemically characterize formate dehydrogenase from Clostridium ljungdahlii (ClFDH) for bioconversion of CO2 to versatile formate. ClFDH was functionally expressed in Escherichia coli without any accessory proteins and recombinant ClFDH were successfully characterized as CO2 reductase with a specific activity of 9.1 mU mg−1 for CO2 reduction. Additionally, the optimum pH was determined at pH 7.0 and 9.0 for CO2 reduction and formate oxidation, respectively. In particular, ClFDH retain its catalytic activity under aerobic conditions, even if C. ljungdahlii is a representative strict anaerobic microorganism. The results discussed herein would not only contribute to broaden biological routes for CO2 utilization but also provide significant insight into the valorization of CO2-containing industrial waste gases to value-added chemicals.