CO2 Affinity Research Articles

Investigation of effective CO2 capture by ternary deep eutectic solvents based on superbase

The absorption and separation of CO2 is one of the main strategies to reduce carbon emissions and mitigate global climate change. In this context, a series of ternary superbase/betaine-based deep eutectic solvents (DESs) were synthesized to capture CO2, and their density, viscosity and thermal stability were investigated. The effects of temperature, pressure, different hydrogen bond donors (HBDs) and alkalinity of the superbase on their CO2 affinity were evaluated by the isovolumetric saturation method. The uptake of CO2 by the DES synthesized from betaine, 1,2-propanediol and 1,8-diazabicyclo(5.4.0)undec-7-ene reached a maximum of 1.5071 mol·kg−1 at 303.15 K and a pressure of 0.187 MPa. The simultaneous chemical and physical adsorption of CO2 by the ternary DESs was verified by FTIR spectroscopy, and the absorption mechanism was also proposed. The reaction equilibrium thermodynamic model (RETM) was improved to obtain the “Active DES” model, which was correlated with the experimentally determined CO2 solubility. The reaction equilibrium constants and Henry's law constants were obtained for each ternary system. The ternary superbase/betaine DESs proposed in this paper are green, economical and high-performance absorbers for capturing CO2.

CO2 methanation over low-loaded Ni-M, Ru-M (M = Co, Mn) catalysts supported on CeO2 and SiC

The concentration of the major greenhouse gas CO2 is rapidly increasing in the atmosphere, leading to global warming and a range of environmental issues. An efficient circulation and utilization of CO2 is critical in the current environmental context. Methanation, an exothermic process, emerges as a critical strategy for effective CO2 utilization. On this front, there is a significant demand for rational design of catalysts that maintain high activity and methane selectivity over a wide temperature range (250–550 °C). The catalyst that can promise a consistent reaction even at 500 °C under an atmospheric pressure is thus obliged. The present study investigated bimetallic catalysts with SiC, which is known for its exceptional thermal conductivity, and CeO2, which is characterized by its CO₂ affinity, as base materials. We incorporated Ni-M and Ru-M (M = Co and Mn) as the active metals, each loaded at 2 %. Impressively, with merely 20 mg, the Ni-Co/SiC catalyst achieved a CO2 conversion rate of 77 % and CH₄ selectivity of 88 % at 500 °C, in a fixed-bed tubular reactor system with conditions of H2/CO2 = 4, a total flow rate of 70 ml min−1, and a steady GHSV of 12,000 h−1. Moreover, 2Ni-2Co/CeO2 catalyst demonstrated exceptional performance with a 76 % conversion of CO2 and a 83 % selectivity for CH4, all under identical conditions. The catalyst's durability was confirmed by a subsequent 40-hour stability test, which showed only a 3–5 % degradation. The developed catalysts were comprehensively characterized by BET/BJH, CO pulse chemisorption, H2-TPR, HAADF-STEM-EDS, SEM-EDS and XRD etc. to unveil their physicochemical and surface traits. It was found that Co and Mn, when integrated, effectively restrained the agglomeration of Ni and Ru particles, ensuring optimal metal dispersion on the support. In conclusion, our synthesized bimetallic catalysts shown a sustained catalytic capability, even in the high-temperature environment.

Enhancement of carbon dioxide adsorption performance on mesoporous alumina modified with alkaline earth metals

The mesoporous alumina-supported alkaline earth metal 5 M/MA (MA= mesoporous alumina, M=Mg, Ca, Sr, and Ba) and xMg/MA (x=1, 3, 5, and 7 wt%) adsorbents were synthesized via evaporation-induced self-assembly (EISA) and impregnation method. The adsorption properties of CO2 were evaluated by thermal gravimetric analyzer to focus on exploring the dynamic adsorption process of the prepared adsorbents. Loading alkaline earth metals mainly enhanced the basic sites of these adsorbents, and the alkaline sites played an extremely critical role in determining the amount of CO2 adsorbed. Of all the adsorbents prepared, 5Mg/MA exhibited the highest adsorption uptake (1.08 mmol/g), a 2.16-fold enhancement compared to MA (0.50 mmol/g). In-situ DRIFTS indicated that CO2 primarily existed in the form of carbonate species, and the analysis of adsorption kinetics elucidated that the adsorption process was predominantly chemisorbed, with external diffusion being the main process of adsorption. Simultaneously, based on DFT calculations, it has been found that Mg-loaded MA has a higher affinity for CO2 compared to MA, which providing a good explanation for the experimental results. Furthermore, the 5 Mg/MA adsorbent not only exhibited excellent adsorption capacity, but also maintained excellent cyclic stability after 10 adsorption and desorption cycle runs, making it a highly favorable option for capturing CO2.

The synthesis of amide bond by a simple one-step method to connect ionic liquid and MIL-101-NH2 firmly for efficient CO2 cycloaddition

Finding robust combination modes between ionic liquids and MOFs is still a challenge. In this work, using a simple one step-synthesis method, the ionic liquid was grafted onto MOF without any additives, and the binding mode of the two was characterized by means of XPS, FT-IR, TGA, SEM etc. It was found that the carboxyl group in the ionic liquid bonded with the amino group in MOF to form an amide bond. Thus, a novel stable composite material MIL-101-NH2-1-carboxypropyl-3-methylimidazolium bromine (1-C-3-M@MIL-101-NH2) was synthesized. This composite employed as a catalyst for CO2 cycloaddition demonstrated excellent catalytic activity, achieving a target product PC (Propylene carbonate) yield of 91.7 % under the conditions of 80 °C, 1.0 MPa, and a reaction time of 4 h, without the addition of any co-catalysts or solvents. The good catalytic activity was benefit from the synergistic effect of Lewis acidic Cr centers and nucleophilic Br-, as well as the high specific surface area and good CO2 affinity of 1-C-3-M@MIL-101-NH2. In addition, owing to this robust bonding configuration, the catalyst can be recycled up to five times without losing activity. It is a potential catalyst for CO2 capture and conversion.

Permeance of Condensable Gases in Rubbery Polymer Membranes at High Pressure.

The gas transport properties of thin film composite membranes (TFCMs) with selective layers of PolyActive™, polydimethylsiloxane (PDMS), and polyoctylmethylsiloxane (POMS) were investigated over a range of temperatures (10-34 °C; temperature increments of 2 °C) and pressures (1-65 bar abs; 38 pressure increments). The variation in the feed pressure of condensable gases CO2 and C2H6 enabled the observation of peaks of permeance in dependence on the feed pressure and temperature. For PDMS and POMS, the permeance peak was reproduced at the same feed gas activity as when the feed temperature was changed. PolyActive™ TFCM showed a more complex behaviour, most probably due to a higher CO2 affinity towards the poly(ethylene glycol) domains of this block copolymer. A significant decrease in the permeate temperature associated with the Joule-Thomson effect was observed for all TFCMs. The stepwise permeance drop was observed at a feed gas activity of p/po ≥ 1, clearly indicating that a penetrant transfer through the selective layer occurs only according to the conditions on the feed side of the membrane. The permeate side gas temperature has no influence on the state of the selective layer or penetrant diffusing through it. The most likely cause of the observed TFCM behaviour is capillary condensation of the penetrant in the swollen selective layer material, which can be provoked by the clustering of penetrant molecules.

Merging polymers of intrinsic microporosity and porous carbon-based zinc oxide composites in novel mixed matrix membranes for efficient gas separation

Mixed matrix membranes (MMMs) have demonstrated significant promise in energy-intensive gas separations by amalgamating the unique properties of fillers with the facile processability of polymers. However, achieving a simultaneous enhancement of permeability and selectivity remains a formidable challenge, due to the difficulty of achieving an optimal match between polymers and fillers. In this study, we incorporate a porous carbon-based zinc oxide composite (C@ZnO) into high-permeability polymers of intrinsic microporosity (PIMs) to fabricate MMMs. The dipole–dipole interaction between C@ZnO and PIMs ensures their exceptional compatibility, mitigating the formation of non-selective voids in the resulting MMMs. Concurrently, C@ZnO with abundant interconnected pores can provide additional low-resistance pathways for gas transport in MMMs. As a result, the CO2 permeability of the optimized C@ZnO/PIM-1 MMMs is elevated to 13,215 barrer, while the CO2/N2 and CO2/CH4 selectivity reached 21.5 and 14.4, respectively, substantially surpassing the 2008 Robeson upper bound. Additionally, molecular simulation results further corroborate that the augmented membrane gas selectivity is attributed to the superior CO2 affinity of C@ZnO. In summary, we believe that this work not only expands the application of MMMs for gas separation but also heralds a paradigm shift in the application of porous carbon materials.

Fabrication of Bamboo-Based Activated Carbon for Low-Level CO2 Adsorption toward Sustainable Indoor Air

This study fabricated a low-cost activated carbon (AC) adsorbent from readily available bamboo trees to control indoor CO2 levels and reduce energy costs associated with sustaining clean indoor air. Bamboo is naturally high in potassium content and has narrow fibrous channels that could enhance selective CO2 adsorption. The prepared bamboo-based activated carbon (BAC) exhibits predominantly micropores with an average pore size of 0.17 nm and a specific surface area of 984 m2/g. Upon amination, amine functionalities, such as pyridine, pyrrole, and quaternary N, were formed on its surface, enhancing its CO2 adsorption capacity of 0.98 and 1.80 mmol/g for low-level (3000 ppm) and pure CO2 flows at the ambient condition, respectively. In addition, the 0.3% CO2/N2 selectivity (αs,g) of the prepared sorbents revealed a superior affinity of CO2 by BAC (8.60) over coconut shell-based adsorbents (1.16–1.38). Furthermore, amination enhanced BAC’s CO2αs,g to 13.4. These results exhibit this sustainable approach’s potential capabilities to ensure the control of indoor CO2 levels, thereby reducing the cost associated with mechanical ventilation systems. Further research should test the new sorbent’s adsorption properties (isotherm, kinetics, and thermodynamics) for real-life applicability.

Highly Efficient Transformation of Tar Model Compounds into Hydrogen by a Ni-Co Alloy Nanocatalyst During Tar Steam Reforming.

Hydrogen (H2) production from coal and biomass gasification was considered a long-term and viable way to solve energy crises and global warming. Tar, generated as a hazardous byproduct, limited its large-scale applications by clogging and corroding gasification equipment. Although catalytic steam reforming technology was used to convert tar into H2, catalyst deactivation restricted its applicability. A novel nanocatalyst was first synthesized by the modified sol-gel method using activated biochar as the support, nickel (Ni) as the active component, and cobalt (Co) as the promoter for converting tar into H2. The results indicated that a high H2 yield of 263.84 g H2/kg TMCs (Tar Model Compounds) and TMC conversion of almost 100% were obtained over 6% Ni-4% Co/char, with more than 30% increase in hydrogen yield compared to traditional catalysts. Moreover, 6% Ni-4% Co/char exhibited excellent resistance to carbon deposition by removing the nucleation sites for graphite formation, forming stable Ni-Co alloy, and promoting the char gasification reaction; resistance to oxidation deactivation due to the high oxygen affinity of Co and reduction of the oxidized nickel by H2 and CO; resistance to sintering deactivation by strengthened interaction between Ni and Co, high specific surface area (920.61 m2/g), and high dispersion (7.3%) of Ni nanoparticles. This work provided a novel nanocatalyst with significant potential for long-term practical applications in the in situ conversion of tar into H2 during steam reforming.

Promising agent for the efficient extraction of Co(II) ions from aqueous medium and its metal complexes: Synthesis, theoretical calculations and solvent extraction

A novel ligand 2,2′-((ethane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(4-((3-(4-methyl-1H-imidazol-1-yl)-5-(trifluoromethyl)phenyl)diazenyl)phenol) and its Co(II), Ni(II) and Cu(II), complexes were synthesized. These compounds were identified using elemental analysis, ICP-OES, FT-IR, thermal analysis, magnetic susceptibility, and molar conductivity techniques. 1H-, 13C-, and 19F-NMR spectra were used to describe the ligand further. 2,2′-((ethane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(4-((3-(4-methyl-1H-imidazol-1-yl)-5-(trifluoromethyl)phenyl)diazenyl)phenol) behaved as a bidentate, and the metal:ligand ratio of the complexes was 1:1, according to elemental analysis, stoichiometric analysis, and spectroscopic data on the synthesized molecules. Using DFT/B3LYP method and the 6-311G(d,p) basis set, the optimized molecular geometries, chemical shifts, vibrational frequencies, HOMO(SOMO)-LUMO energies, and molecular electrostatic potential diagrams of the synthesized compounds in the ground state were determined. In the calculations, the LANL2DZ basis set, which is the effective core potentials for Co(II), Ni(II) and Cu(II) ions, was used. When all of the theoretical data produced by quantum chemical calculations were compared to the experimental data, it was found that there was a good agreement between the two. Additionally, utilizing several transition metal picrates, including Mn(II), Pb(II), Cd(II), Zn(II), Ni(II), Co(II), Cu(II), Hg(II) and Fe(II) cations, the extraction capacity of the ligand was examined. The ligand demonstrated a significant rate of Co(II) cation removal from the aqueous medium in solvent extraction investigations, which also showed a great affinity for Co(II) ions.

Kraft Lignin-Derived Microporous Nitrogen-Doped Carbon Adsorbent for Air and Water Purification.

The study presents a streamlined one-step process for producing highly porous, metal-free, N-doped activated carbon (N-AC) for CO2 capture and herbicide removal from simulated industrially polluted and real environmental systems. N-AC was prepared from kraft lignin─a carbon-rich and abundant byproduct of the pulp industry, using nitric acid as the activator and urea as the N-dopant. The reported carbonization process under a nitrogen atmosphere renders a product with a high yield of 30% even at high temperatures up to 800 °C. N-AC exhibited a substantial high N content (4-5%), the presence of aliphatic and phenolic OH groups, and a notable absence of carboxylic groups, as confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Boehm's titration. Porosity analysis indicated that micropores constituted the majority of the pore structure, with 86% of pores having diameters less than 0.6 nm. According to BET adsorption analysis, the developed porous structure of N-AC boasted a substantial specific surface area of 1000 m2 g-1. N-AC proved to be a promising adsorbent for air and water purification. Specifically, N-AC exhibited a strong affinity for CO2, with an adsorption capacity of 1.4 mmol g-1 at 0.15 bar and 20 °C, and it demonstrated the highest selectivity over N2 from the simulated flue gas system (27.3 mmol g-1 for 15:85 v/v CO2/N2 at 20 °C) among all previously reported nitrogen-doped AC materials from kraft lignin. Moreover, N-AC displayed excellent reusability and efficient CO2 release, maintaining an adsorption capacity of 3.1 mmol g-1 (at 1 bar and 25 °C) over 10 consecutive adsorption-desorption cycles, confirming N-AC as a useful material for CO2 storage and utilization. The unique cationic nature of N-AC enhanced the adsorption of herbicides in neutral and weakly basic environments, which is relevant for real waters. It exhibited an impressive adsorption capacity for the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) at 96 ± 6 mg g-1 under pH 6 and 25 °C according to the Langmuir-Freundlich model. Notably, N-AC preserves its high adsorption capacity toward 2,4-D from simulated groundwater and runoff from tomato greenhouse, while performance in real samples from Fyris river in Uppsala, Sweden, causes a decrease of only 4-5%. Owing to the one-step process, high yield, annual abundance of kraft lignin, and use of environmentally friendly activating agents, N-AC has substantial potential for large-scale industrial applications.

A prediction model for CO2/CO adsorption performance on binary alloys based on machine learning.

Despite the rapid development of computational methods, including density functional theory (DFT), predicting the performance of a catalytic material merely based on its atomic arrangements remains challenging. Although quantum mechanics-based methods can model 'real' materials with dopants, grain boundaries, and interfaces with acceptable accuracy, the high demand for computational resources no longer meets the needs of modern scientific research. On the other hand, Machine Learning (ML) method can accelerate the screening of alloy-based catalytic materials. In this study, an ML model was developed to predict the CO2 and CO adsorption affinity on single-atom doped binary alloys based on the thermochemical properties of component metals. By using a greedy algorithm, the best combination of features was determined, and the ML model was trained and verified based on a data set containing 78 alloys on which the adsorption energy values of CO2 and CO were calculated from DFT. Comparison between predicted and DFT calculated adsorption energy values suggests that the extreme gradient boosting (XGBoost) algorithm has excellent generalization performance, and the R-squared (R2) for CO2 and CO adsorption energy prediction are 0.96 and 0.91, respectively. The errors of predicted adsorption energy are 0.138 eV and 0.075 eV for CO2 and CO, respectively. This model can be expected to advance our understanding of structure-property relationships at the fundamental level and be used in large-scale screening of alloy-based catalysts.

Development of Mixed Matrix Membranes by Using NH2‐Functionalized UiO‐66 and [APTMS][AC] Ionic Liquid for the Separation of CO2

The ever‐escalating CO2 concentration in the atmosphere calls for accelerated development and deployment of carbon capture processes to reduce emissions. Mixed matrix membranes (MMMs), which are fabricated by incorporating the beneficial properties of highly selective inorganic fillers into a polymer matrix, have exhibited significant progress and the ability to enhance the performance of a membrane for gas separation. In this research, an amine‐based ionic liquid (IL) [APTMS][AC] was prepared, which has greater CO2 affinity and greater solubility due to its amine moiety. The metal–organic framework (MOF) UiO‐66 with a multidimensional crystalline structure was used as a filler due to its appropriate porosity and tunable properties, and it was functionalized with NH2. MOFs were further modified with an IL to prepare UiO‐66@IL and UiO‐66‐NH2@IL, and MMMs incorporating each MOF were fabricated with the polymer Pebax‐1657. All the prepared membranes and MOFs were characterized to predict their separation efficiency. Several characterization techniques, namely, FTIR spectroscopy, XRD, and SEM, were used to successfully synthesize UiO‐66@IL and UiO‐66‐NH2@IL composites and confirmed proper dispersion and excellent polymer‒filler compatibility at filler loadings ranging from 0 to 30 wt.%. The separation performances were investigated, and the results showed that the incorporation of RTIL with the highly crystalline structure and large surface area of UiO‐66 enhanced the separation efficiency of the membrane. The permeability of CO2 for all fabricated membranes continuously increased with increasing filler concentration, wherein the permeability was comparatively high for the UiO‐66‐NH2 MMMs. The CO2/CH4 selectivity improved by 35%, 54%, and 60%, respectively, for UiO‐66@IL, UiO‐66‐NH2, and UiO‐66‐NH2@IL MMMs compared to simple UiO‐66 for CO2/CH4 and by 28%, 36%, and 63%, respectively, for CO2/N2, with an increase in filler loading in the MMMs.

Hydrogenation of CO2 to formate catalyzed by a Ru catalyst supported on a copolymerized porous organic polymer.

The catalytic hydrogenation of carbon dioxide to formate is of great interest due to its significant role in CO2 utilization. In this study, a novel heterogeneous Ru(III) catalyst was prepared by immobilizing RuCl3 on a porous organic polymer (POP) obtained from 1,4-phthalaldehyde (PTA) and 4,4'-biphenyldicarboxaldehyde (BPDA) with melamine. A copolymerization strategy utilizing monomers of varying lengths was employed to prepare the POP-supported Ru catalyst with adjustable porosity. The optimization of the framework porosity resulted in enhanced CO2 affinity, accelerated mass transfer, and a remarkable enhancement in catalytic activity. A high turnover number (TON) of 2458 was achieved for the CO2 hydrogenation to formate in 2 h with catalyst Cat-3 under 3 MPa (CO2/H2 = 1 : 1) at 120 °C in 1 M Et3N aqueous solution. Moreover, the Cat-3 demonstrated good recyclability and was able to be reused for five consecutive runs, resulting in a high total TON of 9971.

Spatial tuning of adsorption enthalpies by exploiting spectator group effects in organosilica carbon capture materials

Organosilica materials containing spectator groups next to amines display quasi-solvent behavior that controls CO2 affinity. When the spectator groups are assembled as a density gradient, one obtains a spatial pattern of adsorption enthalpies.

Acyl and CO Ligands in the [Fe]‐Hydrogenase Cofactor Scramble upon Photolysis

Abstract[Fe]‐hydrogenase harbors the iron‐guanylylpyridinol (FeGP) cofactor, in which the Fe(II) complex contains acyl‐carbon, pyridinol‐nitrogen, cysteine‐thiolate and two CO as ligands. Irradiation with UV‐A/blue light decomposes the FeGP cofactor to a 6‐carboxymethyl‐4‐guanylyl‐2‐pyridone (GP) and other components. Previous in vitro biosynthesis experiments indicated that the acyl‐ and CO‐ligands in the FeGP cofactor can scramble, but whether scrambling occurred during biosynthesis or photolysis was unclear. Here, we demonstrate that the [18O1‐carboxy]‐group of GP is incorporated into the FeGP cofactor by in vitro biosynthesis. MS/MS analysis of the 18O‐labeled FeGP cofactor revealed that the produced [18O1]‐acyl group is not exchanged with a CO ligand of the cofactor, indicating that the acyl and CO ligands are scrambled during photolysis rather than biosynthesis, which ruled out any biosynthesis mechanisms allowing acyl/CO ligands scrambling. Time‐resolved infrared spectroscopy indicated that an acyl‐Fe(CO)3 intermediate is formed during photolysis, in which scrambling of the CO and acyl ligands can occur. This finding also suggests that the light‐excited FeGP cofactor has a higher affinity for external CO. These results contribute to our understanding of the biosynthesis and photosensitive properties of this unique H2‐activating natural complex.

Acyl and CO Ligands in the [Fe]-Hydrogenase Cofactor Scramble upon Photolysis.

[Fe]-hydrogenase harbors the iron-guanylylpyridinol (FeGP) cofactor, in which the Fe(II) complex contains acyl-carbon, pyridinol-nitrogen, cysteine-thiolate and two CO as ligands. Irradiation with UV-A/blue light decomposes the FeGP cofactor to a 6-carboxymethyl-4-guanylyl-2-pyridone (GP) and other components. Previous in vitro biosynthesis experiments indicated that the acyl- and CO-ligands in the FeGP cofactor can scramble, but whether scrambling occurred during biosynthesis or photolysis was unclear. Here, we demonstrate that the [18 O1 -carboxy]-group of GP is incorporated into the FeGP cofactor by in vitro biosynthesis. MS/MS analysis of the 18 O-labeled FeGP cofactor revealed that the produced [18 O1 ]-acyl group is not exchanged with a CO ligand of the cofactor, indicating that the acyl and CO ligands are scrambled during photolysis rather than biosynthesis, which ruled out any biosynthesis mechanisms allowing acyl/CO ligands scrambling. Time-resolved infrared spectroscopy indicated that an acyl-Fe(CO)3 intermediate is formed during photolysis, in which scrambling of the CO and acyl ligands can occur. This finding also suggests that the light-excited FeGP cofactor has a higher affinity for external CO. These results contribute to our understanding of the biosynthesis and photosensitive properties of this unique H2 -activating natural complex.

Isoreticularity in a gallate-based metal–organic framework: Impact of the extension of the ligand on the porosity, stability and adsorption of CO2

Isoreticularity is one of the key aspects in the design of new Metal-Organic Frameworks (MOFs), but has been up to now scarcely applied to gallate (1,2-3-trioxobenzene) ligands. With the aim of building new materials isoreticular to the M(Hngal) (H4gal = gallic acid) small pore MOF series, we here designed the new elongated mixed gallate-carboxylate ligand 4-(3,4,5-trihydroxyphenyl)benzoic acid (H4bpgal). A thorough investigation of its reactivity with MgCl2 has led to the successful isolation of the targeted material Mg(H2bpgal)·n(solv) (solv = water, methanol, ethanol). A combination of experimental tools, including single-crystal X-ray diffraction (XRD), powder XRD, and 1H and 13C solid-state NMR studies confirmed the close structural relationship with the smaller analogue, including the presence of acidic OH sites arising from phenol groups bound to Mg cations. Contrary to the small pore analogue, Mg(H2bpgal) is of limited interest for gas capture, because of its moderate stability upon exposure to dioxygen and low affinity for CO2, both resulting from the intrinsic characteristics of the ligand (redox activity and flexibility, respectively). Nevertheless, it presents among the highest surface area and pore volume reported to date for a gallate MOF (1475 m2 g−1 and 0.59 cm3 g−1, respectively); these characteristics might be of interest in other fields of applications, including electrochemical energy storage or combined controlled drug release.

Long‐Range Confinement‐Driven Enrichment of Surface Oxygen‐Relevant Species Promotes C−C Electrocoupling in CO2Reduction

AbstractCO2reduction is a highly attractive route to transform CO2into useful feedstocks, of which C2products are more desired than C1, yet face high kinetic barriers of C−C electrocoupling. Here, the engineering of pore‐enabled local confinement reaction environments is reported for tuning the enrichment of surface‐adsorbed oxygen‐relevant species and the establishment of their pronounced benefits in promoting C−C coupling over oxide‐derived Cu‐based catalysts. A new approach of utilizing the microphase separation of a block copolymer is developed to fabricate bicontinuous mesoporous CuO nanofibers (CuO‐BPNF). The enhanced confinement from long‐range mesochannels enables the adsorption of OHad/Oadon the Cu surface at a wide negative potential range of −0.7 – −1.3 V in CO2reduction, which cannot be achieved over conventional deficient and short‐range pores. Constant‐potential DFT calculations reveal that the surface‐bound oxygen species weakens *CO affinity with the Cu (111) surface and lowers the kinetic barriers for both *CO−CO dimerization and *CO hydrogenation to enable *CO−CHO coupling. Accordingly, a CO2‐to‐C2Faradaic efficiency of 74.7% over CuO‐BPNF is shown, significantly larger than counterparts with conventional pores. This work offers a general design principle of confinement engineering to manage the adsorption of reactive species for steering reaction pathways in interfacial catalysis.

Strategies for Enhancing the Photocatalytic and Electrocatalytic Efficiency of Covalent Triazine Frameworks for CO2 Reduction.

Converting carbon dioxide (CO2) into fuel and high-value-added chemicals is considered a green and effective way to solve global energy and environmental problems. Covalent triazine frameworks (CTFs) are extensively utilized as an emerging catalyst for photo/electrocatalytic CO2 reduction reaction (CO2RR) recently recognized for their distinctive qualities, including excellent thermal and chemical stability, π-conjugated structure, rich nitrogen content, and a strong affinity for CO2, etc. Nevertheless, single-component CTFs have the problems of accelerated recombination of photoexcited electron-hole pairs and restricted conductivity, which limit their application for photo/electrocatalytic CO2RR. Therefore, emphasis will then summarize the strategies for enhancing the photocatalytic and electrocatalytic efficiency of CTFs for CO2RR in this paper, including atom doping, constructing a heterojunction structure, etc. This review first illustrates the synthesis strategies of CTFs and the advantages of CTFs in the field of photo/electrocatalytic CO2RR. Subsequently, the mechanism of CTF-based materials in photo/electrocatalytic CO2RR is described. Lastly, the challenges and future prospects of CTFs in photo/electrocatalytic CO2RR are addressed, which offers a fresh perspective for the future development of CTFs in photo/electrocatalytic CO2RR.

Equisetum praealtum and E. hyemale have abundant Rubisco with a high catalytic turnover rate and low CO2 affinity.

The kinetic properties of Rubisco, a key enzyme for photosynthesis, have been examined in numerous plant species. However, this information on some plant groups, such as ferns, is scarce. This study examined Rubisco carboxylase activity and leaf Rubisco levels in seven ferns, including four Equisetum plants (E. arvense, E. hyemale, E. praealtum, and E. variegatum), considered living fossils. The turnover rates of Rubisco carboxylation (kcatc) in E. praealtum and E. hyemale were comparable to those in the C4 plants maize (Zea mays) and sorghum (Sorghum bicolor), whose kcatc values are high. Rubisco CO2 affinity, estimated from the percentage of Rubisco carboxylase activity under CO2 unsaturated conditions in kcatc in these Equisetum plants, was low and also comparable to that in maize and sorghum. In contrast, kcatc and CO2 affinities of Rubisco in other ferns, including E. arvense and E. variegatum were comparable with those in C3 plants. The N allocation to Rubisco in the ferns examined was comparable to that in the C3 plants. These results indicate that E. praealtum and E. hyemale have abundant Rubisco with high kcatc and low CO2 affinity, whereas the carboxylase activity and abundance of Rubisco in other ferns were similar to those in C3 plants. Herein, the Rubisco properties of E. praealtum and E. hyemale were discussed regarding their evolution and physiological implications.