High CO2 Selectivity Research Articles

Heterogeneous Cobalt Phthalocyanine/Sulfur‐Modified Hollow Carbon Sphere for Boosting CO2 Electroreduction and Zn–CO2 Batteries

AbstractTuning coordination environment of single‐atom catalysts (SACs) is widely applied for the electrochemical CO2 reduction reaction (CO2RR). However, the influence of the interaction between SACs and support on the catalytic performance are not comprehensive. Herein, taking cobalt phthalocyanine (CoPc) as a conceptual example, a hetero S‐atom doping strategy of hollow carbon sphere (S‐NHC) is put forward as a carrier, revealing the intrinsic relationship between microenvironment regulation and catalytic activity of single Co‐atom. The additional S doping may induce more carbon defect and increases the content of pyrrolic N in the S‐NHC sample, leading to stronger electronic interaction of heterogeneous CoPc/S‐NHC for boosting CO2RR performance. Remarkably, the catalyst achieves a highest CO selectivity of nearly 100% at −0.6 V, and the FECO are over 90% in a wide potential range from −0.4 to −0.8 V in a flow cell. The maximum power density is high as 2.68 mW cm−2 at 4.7 mA cm−2 for the Zn–CO2 battery with CoPc/S‐NHC cathode. In situ attenuated total reflection infrared (ATR‐IR) spectroscopy reveals the formation of key *COOH and *CO intermediates, while the calculation result confirm the optimized Gibbs free energy of these intermediates on CoPc/S‐NHC, suggesting the feasibility of the regulation strategy.

Synergy tetraethylenepentamine and diethanolamine impregnated within silica nanotubes derived from natural halloysite for efficient CO2 capture

Amine-impregnated porous solid adsorbents are promising commercial CO2 capture adsorbents for CO2 mitigation due to relatively large CO2 capacity and high CO2 selectivity. However, the intrinsic viscosity and aggregation of the polyamine leads to low amine efficiency and greatly limits its further development. In this work, a facile and efficient approach was carried out to manipulate the porosity of natural halloysite (HNTs) support with hollow tubular structure and impregnate mixed-polyamines, i.e., both tetraethylenepentamine (TEPA) and diethanolamine (DEA) to synergistically enhance CO2 adsorption capacity, fast adsorption kinetics and thermal/chemical stability compared to the individual supported TEPA and DEA. The effects of the blend amount for TEPA and DEA, adsorption temperature and CO2 partial pressure on CO2 adsorption capacity and adsorption kinetics were specifically discussed. Due to the auxiliary effect of DEA, the chemical reaction between non-hydroxylated TEPA and CO2 was altered thus improving amine efficiency and the agglomeration layer between protonated TEPA molecules and carbamate, which existed due to electrostatic interaction when TEPA was loaded alone, was loosened thus improving amine efficiency and adsorption kinetics. Therefore, the maximum CO2 adsorption capacity of MHNTs loaded with 20 wt% TEPA and 20 wt% DEA was 3.25 mmol/g at 75 °C in the flow of 40 vol% N2/60 vol% CO2. Compared with loading individual TEPA with multiple amino groups on MHNTs, individual DEA with hydroxyl groups could increase the utilization efficiency of the amino groups of TEPA and ultimately obtain excellent CO2 capture capacity and adsorption kinetics. The experimental results show that the adsorbents obtained in this study using mixed amine impregnated silica nanotubes derived from natural minerals have a promising application in practical CO2 capture and separation processes.

FePc/MXene as an efficient catalyst for the selective electroreduction of CO2 into CO in a flow cell

Recently, the exploration of MXene-based catalysts has become a hot topic in the electrocatalytic field. Herein, an electrocatalyst of decorating FePc on MXene (called FePc/MXene) was prepared and applied to CO2 reduction reactions (CO2RR) in a flow cell. The results show that CO is the main product of CO2RR on the as-prepared FePc/MXene electrocatalyst, and H2 is the only by-product (small part). Notably, the optimal of FePc/MXene (1:3) (mass ratio) has a high selectivity for CO with a CO Faraday efficiency (FECO) of 98.23%. After 24 h of continuous electrolysis, the FECO remained at a high level of 96.31%. This study would provide a promising catalyst for CO2RR, giving a good reference to developing the MXene-based electrocatalyst.

In Situ Transmission Electron Microscopy and Soft X-Ray Spectro-Microscopy to Understand Electrochemical Processes

Electrochemical CO2 conversion offers a route to use renewable sources of electricity to convert CO2 into valuable carbon-based fuels and chemicals, including carbon monoxide, ethanol and ethylene. For electrochemical CO2 conversion technologies to become a viable component of future sustainable energy infrastructures, improved performance materials (catalysts, electrodes, membrane electrode assemblies) are needed to achieve high conversion rates, selectivity and single-pass utilization of CO2. This talk will focus on the development of techniques to characterize the properties of electrochemical CO2 conversion materials under reaction conditions. These in-situ methods are producing results which will guide the design of next generation materials and reactors. The talk will focus primarily on in situ transmission electron microscopy (TEM) and related spectroscopic techniques (energy dispersive X-ray analysis and selected area electron diffraction), along with synchrotron-based methods including in-situ soft X-ray scanning transmission X-ray microscopy (STXM).

Porous Calcium-Silicate-Hydrate as a Low-Cost Nano-Platform for Ultra-High CO2 Capture and Storage.

CO2 capture and storage have been regarded as promising concepts to reduce anthropogenic CO2 emissions. However, the high cost, inferior adsorption capacity, and higher effective activation temperature of traditional sorbents limit their practical application in efficient CO2 capture. Here, a C-S-H@ZIF-8 (C-S-Z) sorbent is fabricated by in situ growth of the ZIF-8 shell on the C-S-H (calcium-silicate-hydrate) surface for ultra-high CO2 adsorption and storage. Among the C-S-Z, the outer ZIF-8 shell acts as a transport channel that promotes CO2 absorption toward the underlying C-S-H substrate for accelerated carbonation while preventing nitrogen and water from reaching the interior C-S-H. As a consequence, C-S-Z possesses the merits of ample pyrrolic nitrogen, porous structure, and ultra-high surface area (577.18m2g-1), that contribute to an ultra-high CO2 capture capacity, reaching 293.6mgg-1. DFT calculations show a high CO2 adsorption energy and the mineral carbonation is dominant by the adsorption process. In particular, the advantages of the outstanding adsorption capacity, low cost, and high CO2 selectivity make this C-S-H-based sorbent hold great potential in the practical application for direct air CO2 capture and storage.

Decomposition mechanism of Cl-VOCs on Cu- and Fe-modified activated carbon in an O2-free atmosphere: The oxidation pathway and product distribution

Activated carbon exhibits a high adsorption capacity for chlorinated volatile organic compounds (Cl-VOCs), while the desorption of Cl-VOCs is not desirable in the thermal regeneration progress of activated carbon. Chlorobenzene was selected as the model substance to explore whether Cl-VOCs can be oxidized as expected in the regeneration atmosphere of O2-free at the temperature range of 150–450 °C. The modification of activated carbon by Cu or Fe has been shown to considerably improve the decomposition activities. According to the breakthrough curves and detection results from XPS and in situ DRIFTS, the decomposition mechanism of C6H5Cl on Cu and Fe active sites is illustrated. The adsorbed C6H5Cl is firstly dechlorinated to form C6H6 and *Cl, and then it was found there are two pathways for the C6H6 oxidation. C6H6 is indirectly oxidized to form C6H5OH and benzoquinone species, or directly ring-opened to generate ethylene and 1,3-butadiene, and further oxidized to produce CO2, CO and H2O. The C6H6 oxidation is determined by the decomposition of acetate on Cu/AC, but the decomposition of benzoquinone and maleate on Fe/AC. The Fe3O4 and Fe2O3 active sites have a higher dechlorination activity but accelerate the deposition of FeCl2, FeCl3 and organic Cl-containing components. The CuO active center has a higher oxidation performance with a higher CO2 selectivity. About 83.0–83.5% of adsorbed chlorobenzene has been oxidized, and the main Cl-containing product is HCl accounting for approximately 77.8–81.0%, a small amount of Cl forms polychlorinated organic compounds or metal chlorides occupying 2.0–5.7%. As the regeneration temperature decreases, the total amount of Cl-containing species is reduced due the lower oxidation and dechlorination activity of catalysts. The decomposition products of Cl-VOCs in the thermal regeneration process of activated carbon were clarified and quantified, which provides a theoretical basis to control Cl-VOCs in regeneration gas.

Synergistic effect between Ni single atoms and Ni nanoparticles for effectively boosting sustainable co-electrolysis of CO2 and hydrazine

The intrinsic performance of single atom catalysts (SACs) to electrochemical CO2 reduction reaction (ECRR) is limited due to the absence of synergistic active sites. Herein, Ni single atom (NiSAs) and Ni nanoparticles (NiNPs) are co-loaded on nitrogen-doped hollow carbon spheres (N-HCSs) by a one-step calcination method, which exhibits high CO selectivity in H-type cell with aqueous solution or an ionic liquid as electrolyte. Particularly, NiSAs-NPs-N-HCSs demonstrate a CO selectivity of 98.98%, yielding an industrial level CO current density of 152.7 mA cm−2 in flow cell. In situ Raman spectroscopy and in situ infrared characterization technology confirm that *COOH and *CO are important intermediates in the ECRR process. Theoretical computations suggest that coexisting NiNPs can reduce the energy barrier of *COOH, thereby improving the ECRR performance, indicating the synergistic effect between NiSAs and NiNPs in the ECRR process. Moreover, NiSAs-NPs-N-HCSs is applied to the membrane electrode assembly system coupling the hydrazine oxidation reaction (HzOR), which can significantly reduce the voltage about 836 mV at 100 mA cm−2.

Stabilizing Undercoordinated Zn Active Sites through Confinement in CeO2 Nanotubes for Efficient Electrochemical CO2 Reduction.

Zn-based catalysts hold great potential to replace the noble metal-based ones for CO2 reduction reaction (CO2 RR). Undercoordinated Zn (Znδ+ ) sites may serve as the active sites for enhanced CO production by optimizing the binding energy of *COOH intermediates. However, there is relatively less exploration into the dynamic evolution and stability of Znδ+ sites during CO2 reduction process. Herein, we present ZnO, Znδ+ /ZnO and Zn as catalysts by varying the applied reduction potential. Theoretical studies reveal that Znδ+ sites could suppress HER and HCOOH production to induce CO generation. And Znδ+ /ZnO presents the highest CO selectivity (FECO 70.9 % at -1.48 V vs. RHE) compared to Zn and ZnO. Furthermore, we propose a CeO2 nanotube with confinement effect and Ce3+ /Ce4+ redox to stabilize Znδ+ species. The hollow core-shell structure of the Znδ+ /ZnO/CeO2 catalyst enables to extremely expose electrochemically active area while maintaining the Znδ+ sites with long-time stability. Certainly, the target catalyst affords a FECO of 76.9 % at -1.08 V vs. RHE and no significant decay of CO selectivity in excess of 18 h.

Stabilizing Undercoordinated Zn Active Sites through Confinement in CeO2 Nanotubes for Efficient Electrochemical CO2 Reduction

AbstractZn‐based catalysts hold great potential to replace the noble metal‐based ones for CO2 reduction reaction (CO2RR). Undercoordinated Zn (Znδ+) sites may serve as the active sites for enhanced CO production by optimizing the binding energy of *COOH intermediates. However, there is relatively less exploration into the dynamic evolution and stability of Znδ+ sites during CO2 reduction process. Herein, we present ZnO, Znδ+/ZnO and Zn as catalysts by varying the applied reduction potential. Theoretical studies reveal that Znδ+ sites could suppress HER and HCOOH production to induce CO generation. And Znδ+/ZnO presents the highest CO selectivity (FECO 70.9 % at −1.48 V vs. RHE) compared to Zn and ZnO. Furthermore, we propose a CeO2 nanotube with confinement effect and Ce3+/Ce4+ redox to stabilize Znδ+ species. The hollow core–shell structure of the Znδ+/ZnO/CeO2 catalyst enables to extremely expose electrochemically active area while maintaining the Znδ+ sites with long‐time stability. Certainly, the target catalyst affords a FECO of 76.9 % at −1.08 V vs. RHE and no significant decay of CO selectivity in excess of 18 h.

Mixed-valence bimetallic Ce/Zr-NH2-UiO-66 modified with CdIn2S4 to form S-scheme heterojunction for boosting photocatalytic CO2 reduction

A bimetallic Ce/Zr-UiO-66-NH2/CdIn2S4 (Ce-NU66/CIS) heterojunction close interfacial contact has been designed by in-situ hydrothermal co-synthesis of Ce/Zr-NH2-UiO-66 and CdIn2S4. The one-pot-synthesized heterojunction was employed for CO2 reduction without any sacrificial agent. The Ce-NU66/CIS exhibits visible-light-active characteristics accompanied by improved excited charge separation, along with high surface area and well-dispersed heterojunction structure compared to the pristine MOF and CdIn2S4. Doping Ce ions can produce some oxygen vacancies (OVs) and enhance the electron density surrounding Zr4+ ions, which ultimately resulted in an increase in the photocatalytic effect. In the absence of any sacrificial reagents, the optimized 8 wt% Ce0.2NU66/CIS sample exhibited significantly improved photocatalytic CO2 reduction activity, with CO production rate of 6.01 μmol‧g−1‧h−1 and a high CO selectivity of 54.98 %, which were 3.72 and 1.96 times contrasting to the original CdIn2S4, and 17.83 and 2.47 times in comparison of NU66, respectively. Consequently, the bimetallic Ce/Zr-UiO-66-NH2/CdIn2S4 could have the potential to be used as a photocatalyst with improved properties for studying CO2 reduction. It may provide a rational design for constructing mixed-valent bimetallic for soler-driven CO2 conversion.

Tuning the selectivity of CO2 electroreduction on Cu/In2O3 heterogeneous interface

The electrochemical reduction of CO2 is an effective approach to reduce and utilize CO2 for carbon neutral under mild conditions, meanwhile, the development of efficient and stable catalysts with large area and low cost is more conducive to the industrialization of CO2 electroreduction. The metal-oxide heterogeneous interface can promote the activation and conversion of CO2 due to the synergy effect between the metal and the oxide. Therefore, Cu/In2O3 electrodes are fabricated by magnetron sputtering in one step to achieve high selectivity of CO or CH3OH at different potentials. The highest Faradaic efficiency of CO is 78% at − 0.75 V, and unexpectedly, the Faradaic efficiency of CH3OH at − 0.55 V can reach 56%. The abundance of heterogeneous interfaces in Cu/In2O3 provides more active sites, reduces the work function and shifts the d‐band center upward. The catalytic performance was improved by electron transfer promotion and enhanced CO adsorption. Such advantages are responsible for the unique catalytic properties of the metal-oxide electrodes and provide a novel insight to develop large area metal-oxide electrodes for CH3OH preparation.

Facile synthesis of Cu-Zn bimetallic metal-organic framework for effective catalyst toward electrochemical reduction of CO2

Bimetallic metal-organic framework (BM) and high temperature BM (HTBM) based catalysts have several advantages, including uniformly distributed bimetallic ions, less tendency towards aggregation, and more stable interfacial sites. In this study, CuZn-MOF were synthesized using ZIF-8 as a template, and then calcination at a high temperature in the nitrogen atmosphere. The electrochemical reduction CO2 (ERC) was taking place on an H-type cell in 0.1 M KHCO3 aqueous solution. The HTBM calcination at 700 °C exhibited excellent electrochemical CO2 reduction properties, including high CO selectivity (∼ 90%) and low overpotential (< −1.5 V)

Tuning selectivity of CO2 hydrogenation over Co catalysts by surface decoration of Sn

Hydrogenation of CO2 to valuable chemicals is in great attention while modulating the selectivity of catalyst is still a challenging issue. Herein, the selectivity tuning from CH4 to CO was achieved over the Co-based catalysts through Sn decoration. The pristine Sn-doped Co3O4 was prepared by a hydrothermal method, and was found to convert as an exposed metal Co phase along with the segregation and accumulation of Sn on the surface after the reduction pretreatment. Through a combination of experimental and density functional theory calculations, the role of Sn was illustrated to modify the Co sites chemically instead of directly participating into catalysis, leading to a weaken dissociation activity of CO and H2 occurring preferably on the pure Co sites. As a result, it promotes the desorption of intermediate CO from catalyst surface as a main product, thereby achieving high CO selectivity (∼100 %) over the Sn-Co catalyst, in sharply contrast to the predominant CH4 selectivity (>90 %) over the un-modified Co site. This work provides an understanding of chemical modulation of the metal sites through a bimetallic architecture, especially in tailoring catalytic selectivity of CO2 hydrogenation.

Efficient photothermal catalytic CO2 reduction over in situ construction ZnIn2S4@Ni(OH)2/NiO Z-scheme heterojunction

Photocatalytic reduction of CO2 into valuable chemicals has been considered as a sustainable and environmentally friendly technology, which can simultaneously alleviate the energy crisis and environmental problems that have puzzled people for a long time. Herein, we successfully synthesize defective ZnIn2S4@Ni(OH)2/NiO (ZIS@NOH/NiO) Z-scheme heterojunction photocatalysts through solvothermal and low-temperature calcination strategies. The loading of Ni(OH)2 nanosheets can increase the specific surface area of photocatalyst, and form Z-scheme heterojunction with ZIS to improve the utilization of photogenerated electrons. It is worth noting that during the low-temperature calcination process, Ni(OH)2 is partially converted into NiO, and a large number of metal defects are formed, which reduces the bandgap of Ni(OH)2 and shows visible light response. In addition, the generated black defective NiO with full spectrum response and good photothermal effects can accelerate the migration of photogenerated carriers and reduce the catalytic reaction barrier of CO2. Consequently, the prepared ZIS@NOH/NiO exhibits a high yield (133.74 μmol g−1) and selectivity (86.2 %) for CO2 to CH4, which almost is 3.2 and 11.1 times than those of ZnIn2S4@Ni(OH)2 and ZnIn2S4, respectively. Furthermore, in-situ Fourier transform infrared spectroscopy (FTIR) analysis reveal the effective adsorption of CO2 on the ZnIn2S4@Ni(OH)2/NiO surface and the high selectivity of CH4. This work will provide meaningful prospects for designing a carbon dioxide reduction photocatalyst with high conversion and selective.

Piperazine-loaded electrospun fiber mats with MIL-101(Cr, Mg) metal organic framework for CO2 capture

MIL-101(Cr, Mg) is a promising metal organic framework (MOF) considering its moisture, thermal, and chemical stabilities. Piperazine-loaded polyacrylonitrile (PAN)/MIL-101(Cr, Mg) fiber mats were fabricated with different percentages of piperazine (10%, 20%, and 30%) in the polymer solution using an electrospinning technique. The PAN/MIL-101 fiber mats exhibited improved adsorption capacity and selectivity when combined with piperazine because of the improved affinity of CO2 molecules for the basic amine sites of piperazine. PAN/MIL-101–20% was selected as an optimum fiber mat owing to its high CO2 adsorption capacity (2.48 mmol/g) and selectivity (38), which are 2.4 and 2.9 times higher than those of the fiber mat without piperazine, respectively. The stability of the PAN/MOF fiber mat in humid air and NO2 gas and the results of ten adsorption-desorption experiments showed consistent CO2 capture performance.

Adsorption equilibria and kinetics of CO2, CH4, CO, N2, O2, and H2 on silica-based adsorbents for H2 enhancement processes from steel off-gas for the direct reduced iron process

The direct reduced iron (DRI) process is highly advantageous for reducing carbon emissions in the steel mill industry. A well-designed adsorption technology can provide H2 mixtures from H2-containing off-gases for the DRI process and concentrate CO2 for a carbon capture process simultaneously. The adsorption behaviors of steel off-gas components, CO2, CH4, CO, N2, O2, and H2, were studied at 293, 308, and 323 K and at pressures of up to 1000 kPa on two different silica-based pellets. Their weak adsorption affinity and high CO2 selectivity enables relatively easy desorption without vacuum energy. The CO2 and CH4 isotherms were correlated with the dual-site Langmuir model, whereas the single-site Langmuir model adequately predicted the other isotherms. The order of adsorption capacities of both adsorbents was CO2≫CH4>CO>N2≈O2≫H2, and the heat of adsorption of CO2 was notably higher than those of the others. The silica gel with the higher Al content and lower surface area (SG1) showed slightly higher CO2 isotherms up to 100 kPa, whereas the other (SG2) exhibited a greater adsorption capacity at higher pressures. For the other adsorbates, higher isotherms were observed for SG2 at all pressures. In the adsorption kinetic analysis using a non-isothermal adsorption model, the diffusional time constants and kinetic parameters showed a consistent dependence on pressure and temperature. The adsorption rate followed the order of N2>CH4≥CO≫CO2. The isotherm and uptake curves for CO2 between the silica gel pellets and particles revealed that macropore diffusion affected the overall adsorption kinetics of CO2 owing to adsorption heat resistance.

Al Promotion of In2O3 for CO2 Hydrogenation to Methanol.

In2O3 is a promising catalyst for the hydrogenation of CO2 to methanol, relevant to renewable energy storage in chemicals. Herein, we investigated the promoting role of Al on In2O3 using flame spray pyrolysis to prepare a series of In2O3-Al2O3 samples in a single step (0-20 mol % Al). Al promoted the methanol yield, with an optimum being observed at an Al content of 5 mol %. Extensive characterization showed that Al can dope into the In2O3 lattice (maximum ∼ 1.2 mol %), leading to the formation of more oxygen vacancies involved in CO2 adsorption and methanol formation. The rest of Al is present as small Al2O3 domains at the In2O3 surface, blocking the active sites for CO2 hydrogenation and contributing to higher CO selectivity. At higher Al content (≥10 mol % Al), the particle size of In2O3 decreases due to the stabilizing effect of Al2O3. Nevertheless, these smaller particles are prone to sintering during CO2 hydrogenation since they appear to be more easily reduced. These findings show subtle effects of a structural promoter such as Al on the reducibility and texture of In2O3 as a CO2 hydrogenation catalyst.

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.