Low CO2 Concentrations Research Articles

Advanced Solid Amine Adsorbents with Exceptional Oxidative Stability for Efficient Capture of Low-concentration CO2.

Solid amine adsorbents designed for capturing trace amounts of carbon dioxide (CO2) offer a promising approach. However, developing solid amine adsorbents that concurrently exhibit high oxidative stability and superior CO2 adsorption capacity remains a significant challenge. Here, ED-PEI/PEG@FS-TBP, an innovative and highly stable CO2 adsorbent is introduced. This material involves the functionalization of polyethyleneimine (PEI) with 1,2-epoxydodecane (ED), effectively transforming primary amines into secondary amines, thereby mitigating urea formation. Furthermore, the chelator embedded within the fumed silica (FS) supports sequestering metallic impurities that would otherwise catalyze oxidation reactions. The integration of polyethylene glycol (PEG) forms hydrogen bonds with PEI, effectively barricading oxygen access and safeguarding against PEI oxidation. ED-PEI/PEG@FS-TBP achieves an outstanding CO2 adsorption capacity of 1.49mmolg-1 at 298 K and 0.0004bar. Notably, after 20 days of oxidative aging in an environment with 75% relative humidity and 383 K, ED-PEI/PEG@FS-TBP exhibits remarkable oxidative stability, with a deactivation rate constant (kdeact) 93% lower than that of PEI@FS. Its excellent oxidative stability, cycling stability, and high thermal stability, underscore its unparalleled potential for the capture of low-concentration CO2.

Unveiling the incorporation of dual hydrogen-bond-donating squaramide moieties into covalent triazine frameworks for promoting low-concentration CO2 fixation

The development of multi-functional materials for low-concentration CO2 fixation into organic carbonates remains a significant challenge. Herein, we constructed several covalent triazine frameworks modified with squaramide moieties (SCTF-R; R = H, F, CF3) using a facile ZnCl2-mediated trimerization approach. The as-prepared SCTFs possess high surface areas (605–833 m2/g) and incorporate high-density hydrogen bond donors as well as CO2-affinity sites. They demonstrate good CO2 adsorption capacity of up to 2.5 mmol/g at 273 K and 1.0 bar CO2 pressure. Notably, the SCTF-CF3 combined with KI exhibits excellent performance in converting low-concentration CO2 into bromopropene carbonate with a yield of 96 % and selectivity of 99 % under mild and metal-/solvent-free conditions. Furthermore, the SCTF-CF3/KI system demonstrates outstanding reusability and versatility. By combining in-situ FT-IR monitoring with DFT calculations, we elucidate the significant contribution of squaramide moieties and reaction mechanism. This work provides an innovative approach for clean and efficient utilization of low-concentration CO2.

Hydrogen-rich gas generation from enhanced catalytic cracking of biomass tar and related model compounds on Ni-Fe/ASA@HZSM-5 catalyst: Pathways and mechanisms

This study focused on the design of complex tar model compounds (CTMC) and synthesized a highly efficient aluminum dross (ASA) combined with HZSM-5 molecular sieve co-loaded bimetallic Ni-Fe catalyst (Ni-Fe/ASA@HZSM-5), comprehensively evaluated the catalytic cracking of real tar and its model compound by adjusting the injection amount and injection state of tar, and catalyst types to obtain hydrogen-rich gas with high H2 and low CO2 content. The results showed under the conditions of the injection amount of 0.6 mL/min, pyrolysis temperature of 600 °C, reforming temperature of 800 °C in the liquid phase, Ni-Fe/ASA@HZSM-5 displays excellent catalytic cracking performance with CTMC conversion efficiency of 87.80 % (79.46 % of gas yield and 34.20 vol% of H2 yield). The possible cracking paths between different components of CTMC in the Ni-Fe catalytic system were summarized by the experimental data and product distribution, the catalytic mechanism of Ni–Fe based catalysts can be attributed to the formation of a Ni-Fe alloy and the synergistic effect of ASA and HZSM-5 co-carrier. Further, the catalytic cracking pathway of CTMC was enhanced in the gas phase, the higher CTMC conversion efficiency of 93.68 %, gas yield (a mass fraction of 82.51 %) and H2 (a volume fraction of 33.59 %) were obtained from catalytic cracking of CTMC, the liquid yield decreased by 12.39 %, significantly improved the cracking degree and gas production capacity of CTMC. The real tar showed the same catalytic pyrolysis path and product distribution. Under the same cracking conditions, the yields of gas, liquid and char were 84.85 %, 12.00 % and 3.15 % respectively, and obtained the hydrogen yield of 55.29 mL/g. The CTMC simplifies the cracking process and reduces polymerization, provides insights into the cracking mechanisms of heavy components in biomass tar. Furthermore, the synergy of Ni and Fe contributed to greater activity for CTMC and real tar cracking, ASA combined with HZSM-5 molecular sieve co-loaded bimetallic Ni-Fe catalysts have a promising application potential as highly efficient catalysts for tar removal and reutilization.

A convolutional neural network to control sound level for air conditioning units in four different classroom conditions

Air conditioning units (ACUs) are widely used in educational areas like classrooms in order to ensure the occupant’s well-being and to control CO2 concentration (by ventilating using fresh outdoor air). However, the noise level of these ACUs can disrupt the learning environment. Consequently, we propose an approach based on machine learning that is able to distinguish between the different acoustic situations in a classroom, and to dynamically adjust the air volume flow accordingly. To this end, the present algorithm was trained with sound recordings in four different scenarios in a classroom. Both Mel spectrogram and Cochleagram are considered and applied for the task of training the convolutional neural networks (CNN) model, thus enhancing published works in the literature, which only considered the Mel spectrogram. Results show how the Cochleagram is pre-eminent to handle the CNN model training over the Mel spectrogram. Accordingly, we use the Cochleagram for the CNN model training, which is subsequently used for detecting the current situation in the room and adapting the ACU operation to this situation. The results show that running ACUs in high mode provides a learning environment with low CO2 concentration and high noise. Instead, controlling ACU based scenario predictions made by the CNN model provides a good learning environment with adequate CO2 concentration and acceptable noise level. Our results demonstrate the effectiveness of using sound classification as a trigger for ventilation control, with the CNN model achieving a good accuracy rate in sound recognition. This underscores the potential of integrating advanced machine learning techniques into building management systems to foster environments that adapt to the needs of their inhabitants automatically. The results of the present work are useful for improving the comfort of the occupants through dynamic ACUs adjustments based on acoustical situations.

Zr-MOF/MXene composite for enhanced photothermal catalytic CO2 reduction in atmospheric and industrial flue gas streams

In this study, a novel composite was engineered by integrating Zr-MOF (NH2-UIO-66) with MXene layers through electrostatic self-assembly. Under simulated sunlight and at 80 °C, this composite material achieved nearly complete conversion of low-concentration atmospheric CO2 to CO and CH4 without additional sacrificial agents or alkaline absorption liquids, marking one of the few reports demonstrating near-complete reduction of low-concentration CO2 directly from the air. For high-concentration CO2 in industrial flue gas, the composite utilized residual heat at 80 °C without additional energy input, exhibiting excellent CO2 reduction efficiency with CO and CH4 production rates of 127 μmol·g-1·h-1 and 330 μmol·g-1·h-1, respectively, resulting in a total production rate 4.76 times higher than that in the air. Compared to most reports on thermocatalytic CO2 reduction (>300 °C), this material shows significant advantages below 100 °C. The performance improvement is attributed to the introduction of Zr-MOF, which provides additional active sites and reduces activation energy. Additionally, the localized surface plasmon resonance (LSPR) effect of MXene facilitates the migration of thermal charge carriers to Zr4+ sites within the MOF. Density Functional Theory (DFT) calculations validate these findings. Overall, Zr-MOF/MXene composite holds potential for reducing CO2 in air and industrial settings, advancing energy conversion and environmental management.

System design of a novel open-air brayton cycle integrating direct air capture

The Direct Air Capture (DAC) technology is essential for achieving carbon neutrality, as it enables processes with net-negative CO2 emissions. However, its widespread commercialization faces significant challenges due to high energy requirements. Numerous attempts have been made to address this issue through thermal integration, yet the fundamental challenge of the high cost associated with extracting large volumes of low-concentration CO2 from ambient air remains unresolved. In this study, the integration of Open-Air Brayton Cycle (OABC) as a solution to enhance overall system utilization by simultaneously utilizing large volumes of ambient air is introduced. Various OABC coupled temperature swing adsorption based DAC system layouts are analyzed while considering different regeneration temperatures, and the results revealed the optimal configurations that significantly reduce energy cost per captured unit of CO2 with high purity and recovery. By combining an equilibrium short-cut model for temperature swing adsorption with process simulation methodologies, this research proposes the concept of “energy cost”—a metric that represents the amount of CO2 captured against the energy penalty incurred by integrating DAC with OABC systems. The findings demonstrate that combining DAC and OABC systems could yield high purity and recovery rates of CO2 through strategic thermal management and advanced adsorbent usage, offering a synergistic approach to carbon capture from an energy consumption perspective.

Direct low concentration CO2 electroreduction to multicarbon products via rate-determining step tuning

Direct converting low concentration CO2 in industrial exhaust gases to high-value multi-carbon products via renewable-energy-powered electrochemical catalysis provides a sustainable strategy for CO2 utilization with minimized CO2 separation and purification capital and energy cost. Nonetheless, the electrocatalytic conversion of dilute CO2 into value-added chemicals (C2+ products, e.g., ethylene) is frequently impeded by low CO2 conversion rate and weak carbon intermediates’ surface adsorption strength. Here, we fabricate a range of Cu catalysts comprising fine-tuned Cu(111)/Cu2O(111) interface boundary density crystal structures aimed at optimizing rate-determining step and decreasing the thermodynamic barriers of intermediates’ adsorption. Utilizing interface boundary engineering, we attain a Faradaic efficiency of (51.9 ± 2.8) % and a partial current density of (34.5 ± 6.4) mA·cm−2 for C2+ products at a dilute CO2 feed condition (5% CO2 v/v), comparing to the state-of-art low concentration CO2 electrolysis. In contrast to the prevailing belief that the CO2 activation step (CO2+e−+*→CO2−*\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{CO}}_{2}+{e}^{-}+\\, * \\,\ o {}^{ * }{CO}_{2}^{-}$$\\end{document}) governs the reaction rate, we discover that, under dilute CO2 feed conditions, the rate-determining step shifts to the generation of *COOH (CO2−*+H2O→C*OOH+OH−(aq)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${}^{ * } {{CO}}_{2}^{-}+{H}_{2}O\ o {}^{ * } {COOH}+{{OH}}^{-}({aq})$$\\end{document}) at the Cu0/Cu1+ interface boundary, resulting in a better C2+ production performance.

High-temperature carbon dioxide capture in a porous material with terminal zinc hydride sites.

Carbon capture can mitigate point-source carbon dioxide (CO2) emissions, but hurdles remain that impede the widespread adoption of amine-based technologies. Capturing CO2 at temperatures closer to those of many industrial exhaust streams (>200°C) is of interest, although metal oxide absorbents that operate at these temperatures typically exhibit sluggish CO2 absorption kinetics and instability to cycling. Here, we report a porous metal-organic framework featuring terminal zinc hydride sites that reversibly bind CO2 at temperatures above 200°C-conditions that are unprecedented for intrinsically porous materials. Gas adsorption, structural, spectroscopic, and computational analyses elucidate the rapid, reversible nature of this transformation. Extended cycling and breakthrough analyses reveal that the material is capable of deep carbon capture at low CO2 concentrations and high temperatures relevant to postcombustion capture.

Engineering Dual-Defective 0D/2D VN-CNQDs/VBi-Bi4O5Br2 S-Scheme Heterostructure for Boosting CO2 Photoreduction in Air.

The direct photocatalytic reduction of CO2 in air is the future trend of photocatalyst application. Herein, the 0D carbon nitride quantum dots with nitrogen vacancies (VN-CNQDs) and 2D bismuth-deficient Bi4O5Br2 (VBi-Bi4O5Br2) are integrated by hydrothermal method. The S-scheme heterostructure of VN-CNQDs/VBi-Bi4O5Br2 composite promotes the separation rate of photogenerated carriers and enhances the redox capacity. The dual defects provide a large number of adsorption and catalytic sites that enhance the ability to capture and reduce CO2. The synergistic effect of S-scheme heterostructure and defect engineering enables the efficiency of CO2 photoreduction to CO with VN-CNQDs/VBi-Bi4O5Br2 to reach 16.89µmolg-1h-1 in air and 55.69µmolg-1h-1 in VCO2: VAir = 3:1 condition, which is 17 and 21 times higher than that of Bi4O5Br2, respectively. The dual-defective VN-CNQDs/VBi-Bi4O5Br2 exhibits more lower energy barrier for forming *CO2, *COOH, and *CO and is easier to release CO gas. And it exhibits excellent cycling stability for photocatalytic CO2 reduction to CO. The photocatalytic reduction mechanism of CO2 to CO in the VN-CNQDs/VBi-Bi4O5Br2 S-scheme heterostructure is further analyzed. This work provides new perspectives for the design of the photocatalysts with defect engineering for efficient photoconversion at low CO2 concentrations.

Effects of Al doping on structural, optical, morphological, and low-concentration CO2 gas sensing properties of ZnO nanoparticles synthesized by sol-gel method

Abstract This work examines the morphological, structural, optical, and gas-sensing characteristics of ZnO thin films doped with Al that were created by the sol-gel spin coating technique. The thin films, doped with varying aluminum concentrations (0%, 2%, and 5%), were characterized using XRD, UV-visible spectroscopy, and FE-SEM to assess their crystallinity, band gap, and surface morphology. XRD analysis confirmed the incorporation of Al into the ZnO lattice without forming secondary phases, while UV-visible spectroscopy revealed an increase in transmittance and band gap with higher Al doping. FE-SEM images showed a transition from agglomerated grains to smoother surfaces with increased Al content. Gas sensing performance was evaluated using low-concentration CO2 as the target gas. The results demonstrated that Al doping significantly enhances the CO2 sensing response, with the 5% Al-doped ZnO exhibiting the optimal sensitivity due to increased carrier concentration and improved surface interaction. These findings suggest that Al-doped ZnO thin films are promising candidates for efficient CO2 gas sensors, combining enhanced structural and optical properties with superior gas sensing capabilities.

The Influence of Tobacco Smoking Intensity on Hemodynamic Parameters: A Functional Transcranial Doppler Study on Vascular Reserve in Chronic Smokers.

Tobacco smoking is an independent risk factor for stroke. In acute and chronic settings, it affects cerebral blood flow, mean systolic velocities, changes of velocities in response to metabolic challenges, pulsatility, and resistance indices in otherwise healthy smokers. The objective of the study was to determine the influence of smoking intensity on hemodynamic parameters in nonsmokers and smokers. This prospective study enrolled 34 healthy volunteers, 19 smokers and 15 nonsmokers. Epidemiological data were taken from all patients, and exhaled carbon monoxide concentration was measured in smokers. To obtain hemodynamic parameters, we performed functional transcranial Doppler (fTCD) recordings on the posterior cerebral artery for six minutes, consisting of three cycles with closed and opened eyes. We investigated mean systolic velocities, neurovascular responses, and pulsatility indices. Smokers had significantly lower blood flow velocities than nonsmokers (28.36±5.87 and 30.19±6.41, respectively). Neurovascular response as a marker of vasodilatory potential was significantly lower in smokers (14.27%±0.08%) than in the nonsmoker group (17.33%±0.06%). Smokers with higher exhaled carbon monoxide concentrations had lower blood flow velocities than those with lower CO concentrations. Smokers had higher levels of pulsatility indices compared to nonsmokers. The vasodilatory mechanism of cerebral blood vessels is impaired in chronic, otherwise healthy smokers.

Efficient integration of calcium looping with methane bi-reforming using Pd-enhanced Ni-CaO dual functional nanomaterials

Integration technology of methane bi-reforming (BRM; a combination of methane steam and dry reforming) with calcium looping (CaL-BRM) offered a novel solution to reduce CO2 emission, enabling direct capture and conversion of low-concentration CO2 from sources into value-added products (H2, syngas) within the same reactor. In this study, Ni-CaO-based dual-functional material (DFM), with a small quantity of palladium in the nanostructure, was developed via a continuous two-stage aerosol process and employed in the CaL-BRM. Experimental results demonstrate that Pd-Ni-CaO exhibited high activity and cyclic stability over multiple cycles, maintaining effective CO2 capture (12.0 mmolCO2/gCaO) and BRM performance (>98 % CO2 conversion; H2/CO = 2) at a relatively low temperature (600 °C). Density functional theory calculations reveal that the presence of Pd lowered the activation energy of CH* dissociation, the rate-determining step, from 1.14 to 0.67 eV. The higher adsorption energy (−0.87 eV) of H2O on the Ni-Pd surface and the lower energy barrier (0.62 eV) for subsequent dissociation contributed to the promising catalytic performance in the presence of steam. These findings underscore the significance of utilizing appropriate DFM and demonstrate the potential of CaL-BRM for efficient integrated carbon capture and utilization.

Capture and in-situ conversion of low-concentration CO2 over robust poly(ionic liquid)@porous carbon nanocomposites under green, co-catalyst- and solvent-free conditions

The development of advanced materials with dual functionalities for the capture of low-concentration CO2 and its in-situ conversion into value-added chemicals under mild and green conditions holds significant practical importance. In this study, we present a facile pyrolysis of fluid precursors followed by an in-situ polymerization strategy for preparing poly(ionic liquid)@porous carbon nanocomposites (PIL-Brx@Zn-CTM), which possess multiple active sites including Lewis acidic Zn2+, Lewis basic N, and nucleophilic Br– groups. Subsequently, we investigate their potential application in the efficient capture and conversion of low-concentration CO2 into cyclic carbonates. The influence of PIL-Brx@Zn-CTM structures and technological conditions on the cycloaddition reaction between low-concentration CO2 (15 % CO2 and 85 % N2) and epichlorohydrin was examined. The PIL-Br1.0@Zn-CTM nanocomposite was determined to be the most suitable catalyst, resulting in a 94 % yield of chloropropene carbonate with 99 % selectivity under mild, co-catalyst-, and solvent-free conditions. Furthermore, the reusability of PIL-Br1.0@Zn-CTM and its substrate scope were investigated. The PIL-Br1.0@Zn-CTM exhibited sustained high activity without a significant decrease after seven cycles of reuse, and it also demonstrated excellent catalytic activity for cycloaddition reactions involving low-concentration CO2 with various substituted epoxides. Finally, a mechanism for the cycloaddition reaction catalyzed by the PIL-Brx@Zn-CTM nanocomposite was proposed.

Harnessing Visible Light for CO2 Conversion: The Role of Highly Reduced Phosphomolybdate Crystals as Powerful Photocatalysts.

Heterogeneous photocatalysts, characterized by well-defined atomic structures and the capacity for rapid, directional electron transfer, are pivotal in the exploration and development of highly efficient systems for visible-light-driven diluted CO2 reduction. Herein, we constructed highly reduced phosphomolybdates crystalline materials 1-3 to help this process, with the formula of [Co2(C8N3H7)4][Co2(C8N3H7)4(H2O)2][Co(H7P4Mo6O31)2]·8H2O (1), [Ni2(C8N3H7)4(H2O)2][Ni2(C8N3H7)4][Ni(H2O)4][Ni(H6P4Mo6O31)2]·3H2O·2C2H5OH (2), and [Zn2(C8N3H7)2][Zn2(C8N3H7)4][Zn2(C8N3H7)2(H2O)2][Zn(H5P4Mo6O31)2] (3) [C8N3H7 = 2-(1H-pyrazol-3-yl)pyridine]. Specifically, catalyst 1 demonstrated a CO production rate of 3276.4 μmol g-1 h-1 in an environment with 20% CO2 concentration, and an impressively elevated rate of 10740.3 μmol g-1 h-1 in a pure CO2 atmosphere. Steady-state photoluminescence spectroscopy revealed that the directional migration of photoelectrons from the Ru complexes to the catalyst was instrumental in enhancing the catalytic activity. This study provides valuable insights into the rational operation of low-concentration CO2 conversion treatment and the design and synthesis of photocatalysts.

P-Block Aluminum Single-Atom Catalyst for Electrocatalytic CO2 Reduction with High Intrinsic Activity.

Atomically dispersed transition metal sites on nitrogen-doped carbon catalysts hold great potential for the electrochemical CO2 reduction reaction (CO2RR) to CO due to their encouraging selectivity. However, their intrinsic activity is restricted by the hurdle of the high energy barrier of either *COOH formation or *CO desorption due to the scaling relationship. Herein, we discover a p-block aluminum single-atom catalyst (Al-NC) featuring an Al-N4 site that enables disentangling this hurdle, which endows a moderate reaction kinetic barrier for *COOH formation and *CO desorption, as validated by in situ attenuated total reflection infrared spectroscopy and theoretical simulations. As a result, the developed Al-NC shows a CO Faradaic efficiency (FECO) of up to 98.76% at -0.65 V vs RHE and an intrinsic catalytic turnover frequency of 3.60 s-1 at -0.99 V vs RHE, exceeding those of the state-of-the-art Ni-NC and Fe-NC counterparts. Moreover, it also delivers a partial CO current of 309 mA·cm-2 at 93.65% FECO and 605 mA at >85% FECO in a flow cell and membrane electrode assembly (MEA), respectively. Strikingly, when using low-concentration CO2 (30%) as the feedstock, this catalyst can still deliver a partial CO current of 240 mA at >80% FECO in the MEA. Considering the earth-abundant character of the Al element and the high intrinsic activity of the Al-NC catalyst, it is a promising alternative to today's transition metal-based single-atom catalysts.

Dual Metallosalen-Based Covalent Organic Frameworks for Artificial Photosynthetic Diluted CO2 Reduction.

Directly converting CO2 in flue gas using artificial photosynthetic technology represents a promising green approach for CO2 resource utilization. However, it remains a great challenge to achieve efficient reduction of CO2 from flue gas due to the decreased activity of photocatalysts in diluted CO2 atmosphere. Herein, we designed and synthesized a series of dual metallosalen-based covalent organic frameworks (MM-Salen-COFs, M: Zn, Ni, Cu) for artificial photosynthetic diluted CO2 reduction and confirmed their advantage in comparison to that of single metal M-Salen-COFs. As a results, the ZnZn-Salen-COF with dual Zn sites exhibits a prominent visible-light-driven CO2-to-CO conversion rate of 150.9 μmol g-1 h-1 under pure CO2 atmosphere, which is ~6 times higher than that of single metal Zn-Salen-COF. Notably, the dual metal ZnZn-Salen-COF still displays efficient CO2 conversion activity of 102.1 μmol g-1 h-1 under diluted CO2 atmosphere from simulated flue gas conditions (15 % CO2), which is a record high activity among COFs- and MOFs-based photocatalysts under the same reaction conditions. Further investigations and theoretical calculations suggest that the synergistic effect between the neighboring dual metal sites in the ZnZn-Salen-COF facilitates low concentration CO2 adsorption and activation, thereby lowering the energy barrier of the rate-determining step.

Dual Metallosalen‐based Covalent Organic Frameworks for Artificial Photosynthetic Diluted CO2 Reduction

Directly converting CO2 in flue gas using artificial photosynthetic technology represents a promising green approach for CO2 resource utilization. However, it remains a great challenge to achieve efficient reduction of CO2 from flue gas due to the decreased activity of photocatalysts in diluted CO2 atmosphere. Herein, we designed and synthesized a series of dual metallosalen‐based covalent organic frameworks (MM‐Salen‐COFs, M: Zn, Ni, Cu) for artificial photosynthetic diluted CO2 reduction and confirmed their advantage in comparison to that of single metal M‐Salen‐COFs. As a results, the ZnZn‐Salen‐COF with dual Zn sites exhibits a prominent visible‐light‐driven CO2‐to‐CO conversion rate of 150.9 μmol g−1 h−1 under pure CO2 atmosphere, which is ~6 times higher than that of single metal Zn‐Salen‐COF. Notably, the dual metal ZnZn‐Salen‐COF still displays efficient CO2 conversion activity of 102.1 μmol g−1 h−1 under diluted CO2 atmosphere from simulated flue gas conditions (15% CO2), which is a record high activity among COFs‐ and MOFs‐based photocatalysts under the same reaction conditions. Further investigations and theoretical calculations suggest that the synergistic effect between the neighboring dual metal sites in the ZnZn‐Salen‐COF facilitates low concentration CO2 adsorption and activation, thereby lowering the energy barrier of the rate‐determining step.

On-orbit spectral characteristics analysis of the greenhouse gases monitoring instrument: Spectral wavelength stability and instrumental line shape stability

The Greenhouse Gases Monitoring Instrument (GMI) is a carbon satellite payload developed based on the principle of spatial heterodyne spectroscopy technology, which is specifically designed for the global analysis of greenhouse gases (CO2 and CH4) “sources” and “sinks”. Due to the low concentration and minimal gradient variations of CO2 and CH4 in the atmosphere, higher precision is required for their retrieval. Vibrations during satellite launch and harsh space environments during on-orbit operation may cause changes in the performance of various payload components, resulting in decreased quality of spectrum products and retrieval precision. This paper proposes a set of on-orbit spectral characteristic evaluation methods tailored for the GMI to monitor the quality of its spectrum. It also develops an adaptive blind pixel detection and correction algorithm specifically for the GMI and optimizes the interferogram processing flow algorithm. On-orbit spectral calibration is performed, and methods to evaluate spectral characteristic parameters have been established. The analysis focuses on the variations of the spectral characteristics in the CO2-1 bands (1.575 μm) of the GMI during one-year of on-orbit calibration spectrum. The initial spectral wavenumber offset is 0.133 cm−1 after entering orbit, and the average spectral wavenumber offset is 0.0313 cm−1 during stable operation. During the one-year period, the maximum variation in the instrumental line shape function of the GMI is 0.006 cm−1. The observed spectrum obtained in nadir observation mode, underwent to accuracy verification. The results demonstrate consistency between the spectral peak wavenumbers and the relative trend changes of the observed and theoretical spectrum, with an average relative residual of 0.987%.

Molecular Engineering of Poly(Ionic Liquid) for Direct and Continuous Production of Pure Formic Acid from Flue Gas.

Electrochemical CO2 reduction reaction (CO2RR) offers a promising approach to close the carbon cycle and reduce reliance on fossil fuels. However, traditional decoupled CO2RR processes involve energy-intensive CO2 capture, conversion, and product separation, which increases operational costs. Here, we report the development of a bismuth-poly(ionic liquid) (Bi-PIL) hybrid catalyst that exhibits exceptional electrocatalytic performance for CO2 conversion to formate. The Bi-PIL catalyst achieves over 90% Faradaic efficiency for formate over a wide potential range, even at low 15% v/v CO2 concentrations typical of industrial flue gas. The biphenyl in PIL backbone affords hydrophobicity while maintaining high ionic conductivity, effectively mitigating the flooding issues. The PIL layer plays a crucial role as a CO2 concentrator and co-catalyst that accelerates the CO2RR kinetics. Furthermore, we demonstrate the potential of Bi-PIL catalysts in a solid-state electrolyte (SSE) electrolyzer for the continuous and direct production of pure formic acid solutions from flue gas. Techno-economic analysis suggests that this integrated process can produce formic acid at a significantly reduced cost compared to the traditional decoupled approaches. This work presents a promising strategy to overcome the challenges associated with low-concentration CO2 utilization and streamline the production of valuable liquid fuels and chemicals from CO2.

Preparation of pistachio shell-based porous carbon and its adsorption performance for low concentration CO2

In this study, high-performance porous carbon for CO2 adsorption was synthesized from pistachio shells and modified with urea to enrich nitrogen content in the porous structure. The effects of activation temperature, KOH-to-carbon ratio, and urea addition on the pore structure and CO2 adsorption capacity of the porous carbon were investigated. Characterization was conducted using N2 adsorption-desorption isotherms, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FT-IR). Results showed that under preparation conditions of 700 °C, KOH-to-carbon ratio of 2, and 15 wt% urea concentration, the synthesized GAC-15-2-700 porous carbon exhibited a maximum specific surface area of 1395 m2/g, micropore volume of 0.505 cm3/g, and N-5 peak area ratio of 65.57%. It achieved a CO2 adsorption capacity of 3.56 mmol/g. Nitrogen functional groups on the porous carbon primarily existed as pyridinic N (N-6), pyrrolic/pyridinic N (N-5), and quaternary N (N-Q), with the enriched micropores and high N-5 content being crucial for CO2 adsorption.