High CO2 Selectivity Research Articles

Tailoring grain boundaries and doping on Cu-based electrocatalyst for efficient CO2 reduction reaction

Electrochemical conversion of CO2 on Cu-based catalysts offers an auspicious strategy for addressing the increasingly serious environmental issues. However, there is still a challenge in the regulation of selectivity for an efficient CO2 conversion process on Cu-based catalysts due to the complexity of the internal structure of catalysts. Herein, we step wisely control the intrinsic grain boundaries (GBs) and Sn doping in Cu substrate to optimize the CO2 reduction reaction (CO2RR) performance of catalyst, which also clearly clarify the contribution of above two factors towards CO2RR performance. As a result, the as-synthesized R-SnCu catalyst with both GBs and Sn doing exhibits the highest CO selectivity of 99 % at −0.8 V versus hydrogen electrode (vs. RHE). In-situ Raman spectroscopy was further used to provide critical evidence of the key intermediates during CO2RR. We find that compared to the catalysts containing only GBs or Sn doping, the R-SnCu catalyst controlled by both GBs and Sn doping exhibits a more pronounced adsorption preference for C-bound *COOH intermediate peaks related to CO generation. These findings provide new ideas for the effective design of high-performance Cu-based CO2RR catalysts.

Upcycling plastic waste into syngas by staged chemical looping gasification with modified Fe-based oxygen carriers

A novel staged approach, termed staged chemical looping gasification (SCLG) was proposed in this work, for the efficient upcycling of plastic waste into H2-rich syngas with exceptional carbon conversion reaching up to 99%. In such staged system, plastic was firstly pyrolyzed to generate hydrocarbon volatiles, followed by chemical looping reforming in the presence of oxygen carriers, and steam and air was also feed in sequence for carbon removal, syngas regulation and lattice oxygen recovery. A series of Fe-M-Al oxygen carriers (OCs, where M represents Mg, Ca, Mn, Mo, La, Ce) were synthesized and employed for SCLG of waste disposable masks. The performance and stability of these OCs were thoroughly investigated and compared in terms of H2 content and syngas production, while the physicochemical properties characterized by various techniques such as N2 isothermal adsorption-desorption, FESEM, XRD, TPO, and H2-TPR. Results showed that compared with the controlled FeAl sample, all the six modified OCs exhibited higher activity towards syngas production, due to the simultaneously enhanced both partial oxidation reactions and thermal decomposition reactions during the proposed SCLG process. However, the modifiers displayed different role for promoting gasification. Specifically, the addition of Ca significantly promoted the thermal cracking of plastic pyrolysis volatiles and lead to the deep extraction of carbon and H2, whereas the deposited carbon was further gasified into syngas in steam stage. As a result, Fe-Ca-Al showed the highest syngas yield and carbon conversion of 177.89 mmol/gOC and 99.03%, respectively. Fe-Mg-Al possessed relatively high CO selectivity, with the CO/(CO + CO2) ratio of 90.40%. The presence of MoO3 made the Fe-Mo-Al equipped with strong oxygen supply ability, leading to high content of oxygen-containing gases. Furthermore, the cycle stability of OCs was also conducted. The slight decrease in activity of Fe-Ca-Al was due to the metal sintering, whereas Fe-Mo-Al presented relatively stable syngas yield. The proposed staged chemical looping gasification with modified FeAl was demonstrated as a promising upcycling utilization of disposal plastic waste.

Postsynthetic amine modification of porous organic polymers for CO2 capture and separation

AbstractPorous organic polymers (POPs) constitute an important class of sorbents studied in various adsorption and separation processes. Their unique properties, including high surface areas, adjustable pore sizes, and surface chemistries make them ideal candidates for CO2 capture. To achieve a high CO2 adsorption capacity and selectivity, particularly at the low partition pressures required for post‐combustion CO2 capture or direct capture of CO2 from the atmosphere, incorporating amines onto the polymer frameworks or within the pores has shown much promise. This review provides a comprehensive summary of recent studies on the synthesis and CO2 capture performance of amine‐functionalized POPs. The review also provides a detailed discussion of structure‐performance relationships, focusing on how the loading amount and amine type influence CO2 capture capacity, CO2/N2 selectivity, heat of adsorption, sorption kinetics, and recyclability of POPs. Additionally, the authors offer their perspective on the challenges associated with the practical implementation of amine‐modified POPs for CO2 capture.

Constructing asymmetric double-atomic sites for synergistic catalysis of electrochemical CO2 reduction

Elucidating the synergistic catalytic mechanism between multiple active centers is of great significance for heterogeneous catalysis; however, finding the corresponding experimental evidence remains challenging owing to the complexity of catalyst structures and interface environment. Here we construct an asymmetric TeN2–CuN3 double-atomic site catalyst, which is analyzed via full-range synchrotron pair distribution function. In electrochemical CO2 reduction, the catalyst features a synergistic mechanism with the double-atomic site activating two key molecules: operando spectroscopy confirms that the Te center activates CO2, and the Cu center helps to dissociate H2O. The experimental and theoretical results reveal that the TeN2–CuN3 could cooperatively lower the energy barriers for the rate-determining step, promoting proton transfer kinetics. Therefore, the TeN2–CuN3 displays a broad potential range with high CO selectivity, improved kinetics and good stability. This work presents synthesis and characterization strategies for double-atomic site catalysts, and experimentally unveils the underpinning mechanism of synergistic catalysis.

Metallic Honeycomb Catalysts for Methane Steam Reforming: Effect of the Bimetallic Surface Coating on Catalytic Properties

Metallic honeycomb catalysts are promising candidates for fuel cell and small-scale onsite hydrogen production applications. In this study, high-cell-density Ni honeycomb catalysts coated with a series of bimetallic surface layers were synthesized. Their catalytic performance for CH4 steam reforming was investigated under a low steam-to-carbon ratio of 1.36 and a gas hourly space velocity of 6400 h-1 in the temperature range of 400–700°C. The catalysts coated with Ni-Mg and Ni-Zr showed excellent catalytic performance, reaching a high CH4 conversion and CO selectivity close to the equilibrium values within the test temperature range. The enhanced catalytic performance of the Ni-Mg and Ni-Zr coatings was attributed to the formation of oxide-supported fine Ni particles. In contrast, the catalysts coated with Ni-Fe and Ni-Sn exhibited an extremely low activity, which was lower than that of the catalyst coated with only Ni. The low activity of the Ni-Fe and Ni-Sn coatings is supposed to be due to the formation of aggregated Ni3Fe, Ni3Sn, and Ni3Sn2 phases.

Porphyrin Supramolecular Nanoassembly/C3N4 Nanosheet S-Scheme Heterojunctions for Selective Photocatalytic CO2 Reduction toward CO.

The photocatalytic reduction of CO2 with H2O into valuable chemicals is a sustainable carbon-neutral technology for renewable energy; however, the photocatalytic activity and product selectivity remain challenging. Herein, an S-scheme heterojunction photocatalyst with superior CO2 photoreduction performance─porous C3N4 (CN) nanosheets anchored with zinc(II) tetra(4-cyanophenyl)porphyrin (ZnTP) nanoassemblies (denoted as ZnTP/CN)─was designed and prepared via a simple self-assembly process. The constructed ZnTP/CN heterojunction had rich accessible active sites, improved CO2 absorption capacity, and high charge carrier separation efficiency caused by the S-scheme heterojunction. As a result, the obtained ZnTP/CN catalyst exhibited considerable activity for photocatalytic CO2 reduction, yielding CO with a generation rate of 19.4 μmol g-1·h-1 and a high selectivity of 95.8%, which is much higher than that of pristine CN nanosheets (4.53 μmol g-1·h-1, 57.4%). In addition, theoretical calculations and in situ Fourier transform infrared spectra demonstrated that the Zn sites in the porphyrin unit favor CO2 activation and *COOH formation as well as CO desorption, thereby affording a high CO selectivity. This work provides insight into the design and fabrication of efficient S-scheme heterostructure photocatalysts for solar energy storage.

Contributions of CO2, O2, and H2O to the Oxidative Stability of Solid Amine Direct Air Capture Sorbents at Intermediate Temperature.

Aminopolymer-based sorbents are preferred materials for extraction of CO2 from ambient air [direct air capture (DAC) of CO2] owing to their high CO2 adsorption capacity and selectivity at ultra-dilute conditions. While those adsorptive properties are important, the stability of a sorbent is a key element in developing high-performing, cost-effective, and long-lasting sorbents that can be deployed at scale. Along with process upsets, environmental components such as CO2, O2, and H2O may contribute to long-term sorbent instability. As such, unraveling the complex effects of such atmospheric components on the sorbent lifetime as they appear in the environment is a critical step to understanding sorbent deactivation mechanisms and designing more effective sorbents and processes. Here, a poly(ethylenimine) (PEI)/Al2O3 sorbent is assessed over continuous and cyclic dry and humid conditions to determine the effect of the copresence of CO2 and O2 on stability at an intermediate temperature of 70 °C. Thermogravimetric and elemental analyses in combination with in situ horizontal attenuated total reflection infrared (HATR-IR) spectroscopy are performed to measure the extent of deactivation, elemental content, and molecular level changes in the sorbent due to deactivation. The thermal/thermogravimetric analysis results reveal that incorporating CO2 with O2 accelerates sorbent deactivation using these sorbents in dry and humid conditions compared to that using CO2-free air in similar conditions. The in situ HATR-IR spectroscopy results of PEI/Al2O3 sorbent deactivation under a CO2-air environment show the formation of primary amine species in higher quantity (compared to that in conditions without O2 or CO2), which arises due to the C-N bond cleavage at secondary amines due to oxidative degradation. We hypothesize that the formation of bound CO2 species such as carbamic acids catalyzes C-N cleavage reactions in the oxidative degradation pathway by shuttling protons, resulting in a low activation energy barrier for degradation, as probed by metadynamics simulations. In the cyclic experiment after 30 cycles, results show a gradual loss in stability (dry: 29%, humid: 52%) under CO2-containing air (0.04% CO2/21% O2 balance N2). However, the loss in capacity during cyclic studies is significantly less than that during continuous deactivation, as expected.

ZnFexAl2-xO4 spinel supported PdZnβ bifunctional catalyst for methanol steam reforming

PdZnβ alloy catalysts, long regarded as a very promising copper replacement, not only possess copper-like reactivity, but also have superior thermal and chemical stability as well as non-pyrophoric nature that copper catalysts lack. In this contribution, we successfully synthesized the ZnFexAl2-xO4 (x = 0.05–0.2) spinel support, i.e., by replacing Al with a small amount of Fe in ZnAl2O4 spinel. The synthesized support, featuring a high surface area and superior stability, enabled the PdZnβ alloy formation at extremely low Pd loadings (e.g., 1000 ppm Pd), which shows high reactivity and CO2 selectivity toward methanol steam reforming (MSR) reaction. Moreover, it has the unique advantage of constructing bi-functional sites with a specific interfacial structure like PdZn/Fe2O3, the latter of which can effectively enhance water dissociation. Thanks to the synergetic effect, the 0.1 wt% Pd/ZnFe0.1Al1.9O4 catalyst exhibits a much higher ATOF value during the MSR reaction than the 0.1 wt% Pd/ZnAl2O4 counterpart, demonstrating excellent atomic utilization efficiency of noble metal and great potential in the practical application.

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.

Methanation of CO2 on Cu in a tubular co-ionic SOEC

This work aims contributing to develop a cathode for CO2 methanation in tubular co-ionic (H+/O2− conducting) SOECs and to cell operation optimization to decrease energy input and costs for advancing process application. It studies the effect of temperature (325-550 °C) and potential (from −2 to +2 V at 450 °C) on CO2 conversion and selectivity to CH4 and CO, at bench scale, at atmospheric pressure and using high flowrates (42 NL/h) and realistic compositions (4H2/CO2 binary mix), over a Cu film (<2 μm) coated by electroless on an anode (Ni-BZCY)-supported solid electrolyte (BZCY) candle. CH4 preferentially forms over CO. CH4 selectivity increases with temperature up to 97.3% at 400 °C, from which, CH4 and CO selectivity decreases and increases, respectively. The optimum potential is −0.5V, as maximizes CH4 selectivity (94.2%) and minimizes energy cost (0.002 kWh/kg CH4) with high CO2 conversion (32.5%) and low CO selectivity (5.8%), resulting in higher CH4 yield and lower CH4 purification cost.

PEI@MOFs thin film nanocomposite (TFN) membrane for efficient CO2 separation

Polyetherimide (PEI) membrane exhibits high CO2 selectivity while suffer from low permeance thus limiting the further application in CO2 separation. Thin film nanocomposite (TFN) membrane which contains a thin selective functional layer with nanomaterials porous fillers is a new class of high-performance membranes. In this work, a series of novel PEI@MOFs TFN membranes were prepared for efficient CO2 separation. The sub-micro scale PEI layers (about 400 nm) with four kinds of MOFs fillers including 3-dimensional MOFs nanoparticles (UiO-66 and MIL-101 (Cr)) and MOFs nanosheets (2-D CuBDC and Zn2(bim)4) were prepared by a simple spin-coating strategy. The properties and CO2 separation performance of the TFN membranes were further studied. The MOFs in PEI increased the diffusion coefficient and selectivity for CO2, at the same time, the ultra-thin functional layer maximized reducing the CO2 transport resistance. As a result, the PEI@MOFs TFN membranes exhibited high CO2 permeance as well as enhanced CO2 separation performance which close to the Robeson upper bound. The PEI@CuBDC TFN membrane exhibited CO2 permeance of 15.6 GPU (3.3 times higher than the neat PEI membrane), and the selectivity of CO2/CH4 reached 39.8 (2.2 times higher than the neat PEI membrane). In addition, the PEI@MOFs TFN membranes showed good thermal and operation stability.

Structure Sensitivity of CO2 Hydrogenation on Ni Revisited.

Despite the large number of studies on the catalytic hydrogenation of CO2 to CO and hydrocarbons by metal nanoparticles, the nature of the active sites and the reaction mechanism have remained unresolved. This hampers the development of effective catalysts relevant to energy storage. By investigating the structure sensitivity of CO2 hydrogenation on a set of silica-supported Ni nanoparticle catalysts (2-12 nm), we found that the active sites responsible for the conversion of CO2 to CO are different from those for the subsequent hydrogenation of CO to CH4. While the former reaction step is weakly dependent on the nanoparticle size, the latter is strongly structure sensitive with particles below 5 nm losing their methanation activity. Operando X-ray diffraction and X-ray absorption spectroscopy results showed that significant oxidation or restructuring, which could be responsible for the observed differences in CO2 hydrogenation rates, was absent. Instead, the decreased methanation activity and the related higher CO selectivity on small nanoparticles was linked to a lower availability of step edges that are active for CO dissociation. Operando infrared spectroscopy coupled with (isotopic) transient experiments revealed the dynamics of surface species on the Ni surface during CO2 hydrogenation and demonstrated that direct dissociation of CO2 to CO is followed by the conversion of strongly bonded carbonyls to CH4. These findings provide essential insights into the much debated structure sensitivity of CO2 hydrogenation reactions and are key for the knowledge-driven design of highly active and selective catalysts.

Integrating calcium-looping and reverse-water–gas-shift reaction for CO2 capture and conversion: Screening of optimum catalyst

Integrating calcium-looping cycle (CaL) with reverse-water–gas-shift (RWGS) reaction represents an effective path to realizing integrated CO2 capture and utilization (ICCU). Screening a suitable catalyst to construct highly efficient CaO-based dual function materials (DFMs) is essential for CaL-RWGS. In the current work, M@CaO (M = Ni, Co, Mn, and Fe) DFMs are prepared for CaL-RWGS, and the influence of catalyst component on the structure, CO2 capture and RWGS performance, and kinetic behaviors of the CaO-based DFMs is investigated. Results show that the interaction between CaO and catalyst affects the average grain size and dispersion of metallic catalyst, oxygen vacancy concentration, surface basicity, and reducibility of CaO-based DFMs. The desired Mn@CaO DFMs exhibit outstanding CaL-RWGS performance at 650 °C, 15%CO2 and 50%H2, with a great CO2 uptake (12.30 mmol CO2/g), a favorable CO yield (5.92 mmol CO/g), and an impressive CO2 conversion (53.53%), as well as a high CO selectivity (89.98%). Furthermore, Mn@CaO exhibits excellent carbonation and regeneration kinetics but inferior working stability for CO2 capture and CO production in multiple CaL-RWGS cycles. Overall, Mn could be a competitive and cost-effective catalyst candidate for high-performance CaO-based DFMs for CaL-RWGS applications, while further work is needed to improve cyclic stability.

Linking Multicomponent Interactions of Catalyst Ink and Catalyst Layer Fabrication with Electrochemical CO2 Reduction Performance

The controllable fabrication of catalyst layers (CL) by tuning the multiscale structure formation is complex but vital to achieving optimum CO2 reduction (CO2R) performance. The CL formation is deeply influenced by catalyst ink. An in-depth understanding on the role of each catalyst ink component and how multicomponent interactions affect ink status, catalyst layer structure, and CO2R performance is crucial.In this work, the roles of various ingredients of catalyst ink were systematically investigated from simple binary inks to complete catalyst inks. Our results showed Ag agglomerates can be broken down more efficiently in water than in alcohols due to stronger inter-particle repulsive forces induced by water disassociation. Ag particles-Nafion networks were found to play a decisive role in stabilizing catalyst ink, mitigating agglomeration and particle sintering. The catalyst ink was comprehensively characterized and reported by static multiple light scattering (SMLS) for the first time in this study. The evolution of catalyst ink was identified in three stages: stable, flocculation and sedimentation. Isopropanol (IPA)-rich solvents were demonstrated to be more effective in stabilizing catalyst ink due to better dispersed Nafion aggregates and further enhanced Ag particle-Nafion interactions.Subsequently, catalyst layer structure and CO2R performance were correlated with multi-component interactions in catalyst ink. Strong Ag particle-Nafion interactions were proven to promote not only ink stability, but also catalyst layer homogeneity and reaction site distribution. Water-rich inks helped improve the porosity and durability of GDEs. The cathodic potential of GDEs made by 70%-water inks (-0.75 V vs. NHE) was 30% lower than zero-water inks (-1.1 V vs. NHE), and the highest CO selectivity was boosted to 97% at an industrial meaningful current density of 200 mA/cm2 by enhancing Ag particle-Nafion interactions through rational design of ink formulation, dispersing and fabrication processes.Simultaneously, a scalable manufacturing methodology of robust GDE was developed and validated to achieve optimal CO2R performance. It will not only provide a meaningful reference for lab applications (fast and reproducible GDE fabrication aiming at new catalysts, ionomers, membranes or operation conditions development), but also provide a steppingstone to industrial applications (GDE fabrication aiming at large scale, good durability and quality of conformance). Figure 1

Activated three-dimensionally ordered micromesoporous carbons for CO2 capture

Three-dimensionally ordered micromesoporous carbon (3DOmm) has been studied recently as a potential sorbent for CO2 capture at higher pressures. However, the as-synthesized material usually has a low microporous fraction, which could significantly limit CO2 uptake. Herein, we showed that microporosity in 3DOmm carbon can be increased by physical activation, substantially improving its CO2 capture performance in the wide pressure range. The highly porous activated 3DOmm carbons, having amorphous structure, were prepared with ordered spherical mesopores of diameter 22.7–24.7 nm and ultramicropores in the walls of diameter 0.41–0.55 nm. Physical activation was performed by exposing the post-synthesized 3DOmm carbon to high temperatures of 973–1173 K under a CO2 flow for 30 min. The activation procedure did not show any visible destruction of the ordered mesoporous structure in the 3DOmm carbon. However, it had a significant impact on micropore and mesopore volumes and the specific surface area, which in turn affected the CO2 adsorption capacity of the carbons. Accordingly, after activation at 973 K, the micropore volume of 0.23 cm3/g, the mesopore volume of 3.70 cm3/g and the specific surface area of 1058 m2/g in the 3DOmm carbon increased to 0.27 cm3/g, 3.94 cm3/g and 1462 m2/g, respectively. Further increase in activation temperature led to decreasing pore values due to widening and shrinking of the thin carbon walls in the 3DOmm carbon. The 3DOmm carbon activated at 973 K had the highest micropore and mesopore volumes and the highest CO2 adsorption performance over the whole pressure range (3.19 mmol/g at 273 K and 100 kPa; 11.18 mmol/g at 298 K and 2 MPa and 0.38 mmol/g under flue 15% CO2/85% N2 gas conditions at 298 K). All 3DOmm carbons showed fast kinetics, high selectivity for CO2 over N2 (33.2–51.5), the excellent regenerative ability and isosteric heats (18.9–29.2 kJ/mol), indicating physical adsorption.

Carbon dioxide conversion via reverse water-gas shift reaction: Reactor design

The reverse water gas shift (RWGS) reaction converts carbon dioxide (CO2) and hydrogen (H2) to syngas, which is used to produce various high-added-value chemicals. This process has attracted great interest from researchers as a way of mitigating the potential environmental impacts of this greenhouse gas, with emphasis on global warming. This work aims to model and simulate an industrial catalytic reactor using kinetic data for the RWGS reaction. The simulation was carried out in Aspen Plus® v10. The thermodynamic analysis showed that the appropriate conditions for the reaction are feed molar ratio (H2/CO2) of 0.8:1, 750 °C, and 20 bar. The RWGS process proceeds in a multi-tubular fixed bed reactor with 36.26% CO2 conversion and 96.41% CO selectivity, at residence times in the order of 2.7 s. These results are at near-equilibrium CO2 conversion with higher CO selectivity.

Carbon cycle using the CO2 conversion to methane as environmental feasibility on Ni/TiO2-Na nanotubes catalysts

xNi/TiO2-Na nanotubes catalysts were evaluated in CO2-methanation. The catalysts were characterized by FE-SEM, TEM, XRD, MS, CO2-TPD, DRIFTS and TPR. 50Ni/TiO2-Na catalyst showed better CO2 conversion and high CH4 selectivity while, the 5Ni/TiO2-Na catalyst that showed high CO selectivity, low CO2 methanation and Ni species in intimate contact with the support. In this latter, the difficulty of CO2 hydrogenation can be associated with the strength of the catalyst basic sites, which is influenced by the Ni species in intimate contact with the support, promoting the SMSI effect. According with TPD results, the CO2 is retained on the surface of the catalysts with 5 and 20 wt% Ni, and needs higher temperature than in the 50Ni/TiO2-Na nanotube sample to desorb it and liberate the active sites blocked for the reaction to proceed. Although, a high amount of the Ti0.75Ni0.23O cubic phase was observed on the 50Ni/TiO2-Na sample, a large number of metallic Ni particles remained supported on the TiO2-Na which could reduce the SMSI effect on this catalyst. DRIFTs studies showed that Ni impregnation to TiO2-Na nanotubes generated new sites for CO2 adsorption and H2 is necessary to produce carbonates, bicarbonates, formate and carboxilates as intermediaries of the reaction during CO2-hydrogenation.

Nitrogen-rich, click-based porous organic polymers featuring flexible amine cores for catalytic CO2/epoxide cycloaddition

CO2 utilization to produce value-added products such as cyclic carbonates, especially under mild catalytic conditions, is a promising strategy to reduce CO2 emissions to the environment. In this work, nitrogen-rich, click-based porous polymers (CPPs) were prepared from coupling of tripropargylamine and rigid diazido aromatic substrates, featuring 1,4-phenylene (TB), 1,5-naphthalene (TN), and 4,4′-benzanilide (TBA) linkers, in moderate to good yields (48–83%) using Cu-catalyzed azide–alkyne cycloaddition (CuAAC; TB-C, TN-C, TBA-C) and Huisgen cycloaddition (TB-H, TN-H, and TBA-H). The presence of the chelate tris(triazolylmethyl)amine ligands within the polymer's structure led to strong copper binding and consequently high copper loading ability of the CPPs. In addition, high contents of Lewis basic N donors (21–27 wt% N) of TB-C, TN-C, TBA-C are most likely attributed to strong interactions between CO2 and CPPs and exceptionally high CO2 selectivity over N2 at 273 K, based on gas sorption studies. The catalyst system TB-C/TBAB (TBAB = tetrabutylammonium bromide) promoted complete conversion of epoxides to cyclic carbonates under an atmospheric CO2 pressure, after 24 h or 48 h at 100 °C, with the exception of the epichlorohydrin substrate where 42% selectivity was observed by 1H NMR spectroscopy. The TB-C/TBAB catalyst system could be reused for five catalytic runs without a loss in catalytic activities and any pre-activation processes.

Tailoring Zeolite L-Supported-Cu Catalysts for CO2 Hydrogenation: Insights into the Mechanism of CH3OH and CO Formation.

The utilization of Cu-based catalysts in CO2 conversion into valuable chemicals is of significant interest due to their potential in mitigating greenhouse gas emissions. However, the controllable design of Cu-based catalysts and the regulation of their mechanism remain challenging. In this study, a series of efficient Cu/L catalysts were prepared for this process, and the intrinsic influencing factors on the reaction routes were systematically revealed. Various techniques revealed that Cu particles in L-supported catalysts exhibited higher dispersion and formed Cu-O(OH)-K interfacial sites. However, with increasing Cu loading, the dispersion of Cu particles and the percentage of Cu-O(OH)-K interfaces decreased. Kinetic investigations revealed that the adsorption configuration and electronic structure of Cu species codetermined the reaction pathways and resulting selectivity. Cu/L catalysts possessing Cu-O(OH)-K interfaces and small particles demonstrated the preferential formation of formate species, promoting methanol formation. However, larger Cu particles generated carboxylate intermediates, resulting in higher CO selectivity..

Molecular Engineering of Cation Solvation Structure for Highly Selective Carbon Dioxide Electroreduction.

Balancing the activation of H2O is crucial for highly selective CO2 electroreduction (CO2RR), as the protonation steps of CO2RR require fast H2O dissociation kinetics, while suppressing hydrogen evolution (HER) demands slow H2O reduction. We herein proposed one molecular engineering strategy to regulate the H2O activation using aprotic organic small molecules with high Gutmann donor number as a solvation shell regulator. These organic molecules occupy the first solvation shell of K+ and accumulates in the electrical double layer, decreasing the H2O density at the interface and the relative content of proton suppliers (free and coordinated H2O), suppressing the HER. The adsorbed H2O was stabilized via second sphere effect and its dissociation was promoted by weakening the O-H bond, which accelerates the subsequent *CO2 protonation kinetics and reduces the energy barrier from 0.93 to 0.42 eV. In the model electrolyte containing 5 M dimethyl sulfoxide (DMSO) as an additive (KCl-DMSO-5), the highest CO selectivity over Ag foil increased to 99.2%, with FECO higher than 90.0% within -0.75 to -1.15 V (vs. RHE). This molecular engineering strategy for cation solvation shell can be extended to other metal electrodes, such as Zn and Sn, and organic molecule like N,N-dimethylformamide.