Low CO2 Concentrations Research Articles

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.

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.

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.

Preparation of thorny pear residue-based microporous carbon and its adsorption performance for low concentration CO2

Preparation of thorny pear residue-based microporous carbon and its adsorption performance for low concentration CO2

A novel framework for the economic and sustainability assessment of carbon capture and utilization technologies

This study presents a novel framework for assessing early-stage carbon capture and utilization (CCU) reactions. The introduced greenhouse gas abatement, sustainability, and economics framework (GASEF) assesses commercial viability by simultaneously analyzing a CCU technology's CO2 fixation potential with its economic potential. The developed framework combines a previously published CO2Fix parameter and the metric for inspecting reactants and sales (MISR) to estimate CO2 fixation and economic potentials. Both metrics can be estimated using limited information such as temperature, pressure, conversion, molecular weights, the heat of reaction, and the prices of the reactants and products of the CCU reaction. Results from this novel framework are demonstrated via case studies of notable CCU technologies, such as Dry Reforming of Methane and CO2 hydrogenation to methanol processes. Furthermore, the possible implications of providing CO2 subsidies for CCU processes for the gross CO2 input into these processes versus providing CO2 subsidies for the net CO2 fixation of the process is evaluated. In particular, the GASEF assessment on the DRM process showcased a potential for commercial viability even when the technology implementation requires additional investment of 0.1 $/kgCO2 (pertaining to low-concentration CO2 streams) due to carbon capture and sequestration efforts to achieve net-zero emissions. In the case of CO2 hydrogenation to methanol process, the GASEF assessment showcased the potential for commercial viability only at low CO2 credit (0.05 $/kgCO2); however, at values higher than this, the process becomes tenuous. These case studies provide a comprehensive demonstration of the use of the GASEF as a versatile tool to support rapid economics and sustainability evaluation of the new CCU technologies.

Study on the arrangement of CO2 sorbent and catalyst for integrated CO2 capture and methanation

Integrated CO2 capture and utilization (ICCU) is an emerging technology to reduce CO2 emissions by greatly simplifying the processes of conventional CO2 capture and utilization. In particular, ICCU-methanation could directly convert the low-concentration CO2 into CH4 using hydrogen from new energy electricity, representing an efficient Power-to-Gas route. CO2 adsorption/catalytic materials play a crucial role for the operation of ICCU-methanation, and it is more feasible to scale up material production and avoid components interference by directly combining the sorbent and catalyst. However, it is necessary to reveal the effect of different arrangements of sorbent and catalyst on reaction characteristics of ICCU-methanation. In the work, the matching of K2CO3-doped Li4SiO4 sorbent with various supported Ni-based catalyst was tested and four arrangements of sorbent and catalyst particles in a fixed-bed were investigated to understand the influences on ICCU-methanation. Results show that the presence of catalyst accelerates CO2 supply by sorbent and achieves quicker methanation, and the promotion effect becomes more obvious with a closer contact between the sorbent and catalyst. Under optimized conditions, ICCU-methanation of uniformly mixed K-Li4SiO4 and Ni/Al2O3 shows an excellent performance with very stable CO2 conversion of 95.58% and CH4 selectivity of 93.29% during cyclic reactions.

In Situ Fourier Transform Infrared Investigation on the Low-Level Carbon Dioxide Conversion over a Nickel/Titanium Dioxide Catalyst.

Efficiently converting atmospheric carbon dioxide (CO2) is crucial for sustainable human development. In this study, we conducted systematic in situ Fourier transform infrared tests to examine how hydrogen (H2) partial pressure affects the conversion of low-level CO2 (around 400 ppm) using nickel/titanium dioxide (Ni/TiO2). Results show that increasing H2 partial pressure significantly increases surface monodentate formate species, leading to enhanced methane (CH4) production at both 250 and 400 °C. Conversely, on Ni's surface, the key species are formyls and bidentate formate at 250 °C, but these decrease significantly at 400 °C. These findings indicate that low-level CO2 is more easily converted to CH4 over Ni/TiO2 than Ni, regardless of temperature. Additionally, the strong Ni-TiO2 interaction gives Ni/TiO2 an advantage in converting low CO2 concentrations, with excellent durability even at 400 °C. This study enhances our understanding of direct CO2 conversion and aids in the development of advanced CO2 emission reduction technologies.

Electroreduction of CO2 to HCOOH on 3D-Ag nanosheet array supported on carbon membrane

Regulating local CO2 concentration and pH near the catalytic active sites could induce effective reaction pathways for electroreduction of CO2 to chemicals. Here, a membrane nanofluid reactor for efficient electroreduction of CO2 to formic acid was prepared by constructing high-density active sites of 3D-Ag nanosheet array on the surface and within the pores of carbon membrane (3D-Ag NA/CM). The local microenvironment of CO2 and H+ concentration was controlled by adjusting the pore size, CO2 flow rate, and mass transfer mode. In the flow-through mode, the CO2 was electro-reduced to formic acid with Faraday efficiency of 94% and the partial current density of 35.8 mA/cm2. Both the selectivity and activity were higher than those in flow-by mode. The low local concentration of CO2 in the channel was the key to the high selectivity of formic acid. When CO2 flowed through the membrane nanopores, the high collision frequency of CO2 with catalyst on the pore walls facilitated the electroreduction of CO2. It found that the presence of OV promoted the adsorption of CO2 and reduced the energy barrier for its activation into ∗CHOO. It lays a foundation for the research on optimizing the performance of CO2 electroreduction with nanofluid reactors.

Carbon-based materials for low concentration CO2 capture and electrocatalytic reduction

The gradual increase in carbon dioxide (CO2) concentration in the atmosphere has been recognized as a significant problem for humankind. CO2 flue gas is one of the most apparent contributing sources of emissions. CO2 capture and conversion are environmental-friendly and efficient ways to reduce atmospheric carbon dioxide emissions from flue gases. Considering the traditional expensive gas purification process of low-concentration CO2, the low-cost capturing and electrocatalytic CO2 reduction (ECR) at low concentration by newly-developed carbon-based materials provide an attractive approach to convert low-concentration CO2 in flue gas into high-value fuels and chemicals. Developing and integrating carbon-based capturing and catalytic materials with an understanding of the mechanism has a promising future and will promote this technology toward practical application. This review describes recent progress in the design, preparation, and structural characterization of existing carbon-based materials for the capture and catalysis of low-concentration CO2. The crucial factors of capturing and catalysis performance of all the carbon-based materials are also summarized. Furthermore, the review identifies existing research problems and challenges, and outlines future research directions. We also discuss the prospects for the industrialization of low-concentration CO2 capture and ECR. The remaining technological challenges and future directions for enhancing and applying of carbon-based materials for CO2 capture and electrocatalytic reduction are highlighted.

CoCorrole-Functionalized PCN-222 for Carbon Monoxide Selective Adsorption.

The high risk of CO poisoning justifies the need for indoor air quality control and warning systems based on the detection of low concentrations (ppm-ppb) of CO. Cobalt corrole complexes selectively bind CO vs. O2, CO2, N2, opening new fields of applications. By combining the CO chemisorption properties of cobalt corroles with the known sorption capacity of MOFs, we hope to obtain high performance sensing materials for CO detection. In addition, the exposed metal sites of MOFs lead to CO2 physisorption, allowing the co-detection of CO and CO2. In this work, PCN-222, a stable Zr-based MOF made from Ni(TCPP) with natural vacancies, has been used as a porous matrix for the grafting of electron-poor metallocorroles. The materials were characterized by powder XRD, SEM and optical microscopy, BET analyses and gas adsorption measurements at 298 K. No degradation of the crystalline structure of PCN-222 was observed. At 1 atm, the adsorbed CO(g) volumes measured for the best materials were 12.15 cm3 g-1 and 14.01 cm3 g-1 for CoCorr2@PCN-222 and CoCorr3@PCN-222 respectively, and both materials exhibited high CO chemisorption and selectivity against O2, N2, and CO2 at low pressure due to the highest energy of the chemisorption process vs physisorption.

Early age accelerated carbonation of cementitious materials surface in low CO2 concentration condition

Accelerated carbonation curing contributes to the carbon sequestration effect of cementitious materials and enhances surface density. However, in large-scale applications, traditional high CO2 concentration conditions (>5 % CO2) are constrained by economic costs. This study traces the early-stage accelerated carbonation process of cement mortar under low CO2 concentration (3 % CO2) condition from the perspectives of the evolution of CaCO3 crystal types, phase transformations, and microstructural changes, and compares the results with those under the 20 % CO2 condition. The results show that the carbonation depth of mortar specimens cured under the 3 % CO2 condition is shallower, but the cumulative concentration of CaCO3 within the surface 3 mm is not significantly lower than that under the 20 % CO2 condition; The carbonation zone generates more low-crystalline forms of CaCO3; The accelerated carbonation process does not affect the formation of CH and ettringite. Microscopic results indicate that under the 3 % CO2 condition, the synergistic effects of hydration and carbonation are better, and appropriately extending the curing time helps to refine the pore structure of the carbonation zone and improve the density of the substrate surface.

Assessing ventilation through ambient carbon dioxide concentrations across multiple healthcare levels in Ghana.

Infection prevention and control (IPC) measures safeguard primary healthcare systems, especially as the infectious disease landscape evolves due to climate and environmental change, increased global mobility, and vaccine hesitancy and inequity, which can introduce unexpected pathogens. This study explores the importance of an "always-on," low-cost IPC approach, focusing on the role of natural ventilation in health facilities, particularly in low-resource settings. Ambient carbon dioxide (CO2) levels are increasingly used as a measure of ventilation effectiveness allowing for spot checks and targeted ventilation improvements. Data were collected through purposive sampling in Northern Ghana over a three-month period. Levels of CO2 ppm (parts per million) were measured by a handheld device in various healthcare settings, including Community-Based Health Planning and Services (CHPS) facilities, municipal and teaching hospitals, and community settings to assess ventilation effectiveness. Analyses compared CO2 readings in community and hospital settings as well as in those settings with and without natural ventilation. A total of 40 facilities were evaluated in this study; 90% were healthcare facilities and 75% had natural ventilation (with an open window, door or wall). Facilities that relied on natural ventilation were mostly community health centers (60% vs 0%) and more commonly had patients present (83% vs 40%) compared with facilities without natural ventilation. Facilities with natural ventilation had significantly lower CO2 concentrations (CO2 ppm: 663 vs 1378, p = 0.0043) and were more likely to meet international thresholds of CO2 < 800 ppm (87% vs 10%, p = <0.0001) and CO2 < 1000 ppm (97% vs 20%, p = <0.0001). The adjusted odds ratio of low CO2 in the natural facilities compared with non-natural were: odds ratios, OR (95% CI): 21.7 (1.89, 247) for CO2 < 800 ppm, and 16.8 (1.55, 183) for CO2 < 1000 ppm. Natural ventilation in these facilities was consistently significantly associated with higher likelihood of low CO2 concentrations. Improved ventilation represents one cost-effective layer of IPC. This study highlights the continuing role natural ventilation can play in health facility design in community health care clinics. Most health facilities met standard CO2 thresholds, particularly in community health facilities. Further research is needed to optimize the use of natural ventilation. The use of a handheld devices to track a simple metric, CO2 levels, could improve appreciation of ventilation among healthcare workers and public health professionals and allow for them to target improvements. This study highlights potential lessons in the built environment of community primary health facilities as a blueprint for low-cost, integrated multi-layer IPC measures to mitigate respiratory illness and anticipate future outbreaks.

Zinc-cluster-based MOF with super selective separation adsorption catalyzes direct chemical conversion of CO2 from quasi-polluted air

The CO2 in the atmosphere has a serious impact on the human living environment. Direct utilization of the discharged CO2 to produce useful chemicals is challenging due to the practical presence of mixed compositions and low concentrations for CO2. Metal-organic frameworks (MOFs) with high internal surface areas, porosity and open metal site potentially possess superior adsorption separation capacity for CO2 gas, and on this basis, it can be used as a catalyst to achieve efficient chemical conversion of CO2. We demonstrate the synthesis and characterization of MOF ([Zn4O(ntba)2]n, MOF 1, H3ntba=4,4',4''-nitrilotribenzoic acid) with excellent selective adsorption properties from quasi- polluted air (O2, N2, CO2, CH4) and as heterogeneous catalysts for direct efficient CO2 chemical conversion. Detailed structural analysis reveals show that zinc ions behave multiple open metal sites and two coordination modes in the polyhedral zinc clusters building unit forming a 3D porous network by polyhedral zinc clusters building unit. Thanks to its structural features, at the 273 K and 100kPa, due to the ideal specific surface area and porosity, MOF 1 have ideal adsorption-separation performance for CO2, its values of adsorption and separation ratio are 75.7 cm3g−1, 373(CO2/N2), 79(CO2/O2), 13(CO2/CH4), respectively. The cycloaddition catalytic reaction investigations show that MOF 1 can be employed as a highly efficient catalyst for converting CO2 with a yield of 78 %. The result of this experiment offers the potential to directly utilize low-concentration and mixed CO2 while avoiding the economic and environmental costs of obtaining purified CO2 feeds tocks.