CO2 Pressure Research Articles

Experimental study on transient characteristics and thermal stratification of high−pressure CO2 leakage under different initial density

Accidental leakage is one of the major safety issues in the carbon capture and storage project (CCS), which may pose a significant danger to pipelines, containers and surrounding crowd. It is necessary to study the leakage behavior of high−pressure CO2, providing data support for the risk assessment of CO2 leakage. In this paper, the accidental leakage of high−pressure CO2 is simulated by releasing CO2 from a storage tank, aiming to understand the transient characteristics and thermal stratification inside the tank of CO2 leakage process. The initial CO2 is at different initial density of 600∼1000 kg/m3 and at almost the same initial pressure of 10.8±0.4 MPa. Firstly, the outlet transient characteristics and temperature evolution inside the tank are presented. Then, the variation of P−T curves and phase evolution are analyzed in detail. Finally, the leakage behavior under different initial density is described. The results show that the leakage process can be clearly divided into three stages based on the outlet pressure. The outlet pressure evolution, phase evolution and temperature distribution inside the tank are very different in these three stages. This research is of great significance for leakage risk prediction, early leakage detection and leakage hazard control.

The Role of Benthic TA and DIC Fluxes on Carbon Sequestration in Seagrass Meadows of Dongsha Island

Coastal blue carbon ecosystems sequester carbon, storing it as plant biomass and particulate organic matter in sediments. Recent studies emphasize the importance of incorporating dissolved inorganic and organic forms into carbon assessments. As sediment-stored organic matter decomposes, it releases dissolved inorganic carbon (DIC) and total alkalinity (TA), both of which are critical for regulating the partial pressure of CO2 (pCO2) and thus carbon sequestration. This study investigated the role of benthic DIC and TA fluxes in carbon sequestration within seagrass meadows in Dongsha Island’s inner lagoon (IL) during the winter and summer seasons. Chamber incubation experiments revealed elevated benthic DIC and TA fluxes compared to global averages (107 ± 75.9 to 119 ± 144 vs. 1.3 ± 1.06 mmol m−2 d−1 for DIC, and 69.7 ± 40.7 to 75.8 ± 81.5 vs. 0.52 ± 0.43 mmol m−2 d−1 for TA). Despite DIC fluxes being approximately 1.5 times higher than TA fluxes, water pCO2 levels remained low (149 ± 26 to 156 ± 18 µatm). Mass balance calculations further indicated that benthic DIC was predominantly reabsorbed into plant biomass through photosynthesis (−135 to −128 mmol m−2 d−1). Conversely, TA accumulated in the water and was largely exported (−60.3 to −53.7 mmol m−2 d−1), demonstrating natural ocean alkalinity enhancement (OAE). This study highlights the crucial role of IL seagrass meadows in coastal carbon sequestration through net autotrophy and carbonate dissolution. Future research should explore the global implications of these processes and assess the potential of natural OAE in other coastal blue carbon ecosystems.

Effect of Stocking Density on Selected Blood Physiological, Biochemical and Enzymatical Variables of Broilers Grown to 3 kg under Antibiotic-free Conditions

Background: Reducing stocking densities may play a key role in minimizing difficulties such as physiological welfare when reducing or ending antimicrobials in poultry diets. As the demand for poultry and associated products increases, one of the major concerns centers on the question of whether stocking density influences welfare responses that are characteristic of physiological welfare. This study investigated the effect of stocking density on selected blood physiological variables along with plasma biochemistry variables and enzymes activities of broilers fed antibiotic-free diets grown to 3 kg. Methods: A total of 888 1-d-old Ross ´ Ross 708 chicks were randomly distributed into 24 pens based on stocking density treatments assignment. The treatments consisted of 4 densities (29, 33, 39 and 42 kg/m2) with six replicates. Treatments were blocked within the room to account for any variations in room conditions. Treatment assignments were randomized within each block. Used litter bedding was obtained from commercial farms to mimic commercial conditions and litter microflora. Birds were provided a three phase-feeding program (Starter: 0-14 d, Grower: 15-28 d and Finisher: 29-42 d) antibiotic-free diets. Feed and water provided ad libitum. Blood samples were collected from the brachial wing vein of 3 males and 3 females’ birds per pen on d 28 and 42 and analyzed immediately for blood physiological variables. Blood plasma samples were analyzed for T3, T4, corticosterone, biochemical variables and enzyme activities. Result: The only effect of stocking density was observed on partial pressure of CO2 (pCO2) and uric acid which were within physiological ranges for this species. However, blood glucose and plasma corticosterone concentrations were not affected by stocking density, suggesting no signs of physiological stress. Stocking densities up to 42 kg/m2 with proper environmental management may be suitable for both poultry integrators and contract growers to enhance broilers production efficiency without compromising the welfare of broilers grown to 3 kg body weight.

Zinc Bioinspired Catalytic System for the Valorization of CO2 Into Cyclic Carbonates

AbstractCyclic organic carbonates are defined as key compounds for a sustainable chemical economy. Their synthesis from CO2 under mild conditions is a useful way to valorise this greenhouse gas as carbon source. Even if a wide range of catalysts were described to promote the carbon dioxide cycloaddition into epoxides, only few ones concern enzymatic systems. The zinc–l‐histidine active site of carbonic anhydrase inspired the present work, pointing out that the imidazole moiety of the amino acid ligand has a crucial role. An extensive study was undertaken to establish the structure–activity relationship of imidazole derivatives, zinc salts, and their respective catalytic activity in the CO2 cycloaddition reaction. The effect of aromatic, alkyl, or iodine substituents and their position in N‐heterocycles were highlighted. A synergic effect was noted when combining imidazole compounds with zinc salts. The optimization of reaction conditions emphasised the in situ ZnI2–1‐methylimidazole catalytic system, which is selective toward cyclic styrene carbonates and efficient under solvent‐free mild conditions (50 °C, atmospheric CO2 pressure). Once reusing tests confirmed the catalytic system robustness, the reaction scope was enlarged to several epoxides resulting in 84%–99% yields of their corresponding cyclic carbonates.

Solvent Free Ambient Pressure CO2 Cycloaddition Catalyzed by Cobalt-Impregnated 2D-Nanofibrous COFs.

Covalent organic frameworks (COFs) constitute an evolving class of permanently porous and ordered materials, and they have recently attracted increased interest due to their intriguing morphological features and numerous applications in gas storage, adsorption, and catalysis. However, their low aqueous stabilities and tedious syntheses generally hamper their use in heterogeneous catalysis. Nonetheless, a capable and water-stable heterogeneous catalytic system for coupling CO2/epoxides to generate industrially important cyclic carbonates is still of great interest. Herein, exceedingly water- and thermally stable 2D-cobalt-impregnated hydrazone-linked fibrous COFs are reported as a catalyst for CO2/epoxide coupling reactions at ambient pressure. The functionalized cobalt (Co)-doped COFs demonstrated excellent catalytic activities with the high TONs (80925) and TOFs (6466 h-1), outperforming reported heterogeneous catalysts for CO2/epoxide coupling at ambient pressure. We found that the Co2+ ions within the COF matrix catalyze CO2 cycloaddition through density functional theory calculations. We also confirmed the excellent structural stability and consistent activity of Co-doped COFs up to ten repeating cycles.

Key processes controlling the variability of the summer marine CO2 system in Fram Strait surface waters

The aim of this study was to decouple and quantify the influence of various biological and physical processes on the structure and variability of the marine carbonate system in the surface waters of the eastern part of the Fram Strait area. This productive region is characterized by its complex hydrographic and sea ice dynamics, providing an ideal set up to study their influence on the variability of the marine carbonate system. Different variables of the marine CO2 system: Total Alkalinity (TA), Dissolved Inorganic Carbon (DIC), partial pressure of CO2 (pCO2), and pH, were analysed together with temperature, salinity, sea ice extension, and chlorophyll a distribution during three consecutive summers (2019, 2020 and 2021), each of them having a unique oceanographic setting. The data revealed that TA and DIC are mostly controlled by the mixing of Atlantic water and sea ice meltwater. The combined effects of organic matter production/remineralization, calcium carbonate precipitation/dissolution, and air/sea CO2 gas exchange cause deviations from this salinity-related mixing. The scale of these deviations and the proportion between the effects observed for TA and DIC suggest interannual shifts in net primary production and dominant phytoplankton species in the area. These shifts are correlated with the sea ice extent and the spread of the Polar Surface Waters in the region. Net primary production is the main factor controlling the temporal and spatial variability of pH and pCO2 in the study area followed by the influence of temperature and, mixing of water masses expressed with salinity (seawater freshening). Surface waters of the Fram Strait area were generally undersaturated in CO2. The lowest pCO2 values, coinciding with an increase in oxygen saturation, were observed in areas of mixing of Arctic and Atlantic-derived water masses. However, as shown for 2021, a reduction of the sea ice extent may induce a westward shift of the chlorophyll maximum, resulting in pCO2 increase and pH decrease in the eastern part. This indicates that sea ice extent and associated spread of Polar Surface Waters may be important factors shaping primary production, and thus pCO2 and pH, in the Fram Strait area.

CO2 transport in supercritical state: Nikiski, Alaska pipeline study

AbstractCarbon dioxide (CO2) in the supercritical state, being denser yet less viscous, is suitable for long‐distance transportation. Despite this well‐known principle, implementing an operational scheme with appropriate inlet pressure and mass flow rate for supercritical CO2 (srCO2) transportation is challenging due to the complex interplay among state variables, fluid properties, pipeline dimensions and materials, and the intricate boundary and ambient conditions surrounding the pipeline. This paper utilizes PIPESIM software to conduct a feasibility study of srCO2 transportation over a 10‐mile‐long model pipeline in the Cook Inlet region of Alaska, USA. The study aims to understand the limitations of operational parameters and develop a scheme for selecting feasible parameters for srCO2 transportation. Considering geographic location, elevation profiles, and ambient conditions, the simulations calculated pressure and temperature profiles, erosion kinetics, and fluid states for various conditions derived from a combinatorial set of pipeline diameters ranging from 11 to 16 in, inlet pressures between 1,400 and 1,900 psia, and mass flow rates from 10 to 275 lbm/s, with an inlet temperature of 200 °F. The major findings indicate that larger pressure losses are expected in smaller pipelines that are well‐insulated and/or operated at lower inlet pressures. Turbulent flow is more likely to occur in smaller pipelines and at higher mass flow rates, potentially altering the state of the transported fluid. The parametric modeling results provide a scenario‐driven approach to determining a feasible range of mass flow rates, pipeline inner diameters, and inlet pressures for srCO2 transportation. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Calibration experiments for dual-comb IPDA XCO2 measurements using a variable pressure absorption cell

Measuring XCO2, the column-averaged dry-air mixing ratio of CO2 in the atmosphere, is essential for monitoring climate change and guiding mitigation efforts. Integrated Path Differential Absorption (IPDA) is a highly effective XCO2 measurement solution for space-borne lidar. However, the limited number of wavelengths limits its capabilities. IPDA, enhanced with Electro-Optical Frequency Comb (EOFC) technology, offers a robust solution. This study validates IPDA measurements using both asymmetric and symmetric Electro-Optic Dual-Comb Spectroscopy (EO-DCS) systems at 1572 nm. This indoor experimental system does not operate in a true lidar mode, but focuses on IPDA measurements of XCO2 through a transmission-style cell. We achieved atmospheric spectral transmittance by a variable pressure CO2 absorption cell, correlating pressures from 425 to 470 mb to XCO2 of 386.81–447.08 ppm. The XCO2 measurements of asymmetric/symmetric systems both exhibit excellent linearity. Their linear fittings yielded the Root Mean Square Error (RMSE) as low as 0.198/0.064 ppm, and the Mean Absolute Percentage Errors (MAPE) was as low as 0.0386%/0.0140%. This level of measurement performance has never been demonstrated in other works. Accuracy was assessed by comparing IPDA results with a pressure gauge, and precision was confirmed through repetitive measurements (1000 times over 10 min) and Allan variance analysis. Notably, our system operates effectively without frequency stabilization, showing tolerance to laser frequency drift—a significant advantage for IPDA applications. The entire experiment was conducted in a comparison between asymmetric and symmetric systems, especially in the analysis of absorption line residuals. We discuss the error transfer from phase to spectral transmittance and its implications and explained why the residuals in the asymmetric system were larger. These results underscore the superior performance of EO-DCS IPDA in measuring XCO2 and its promising potential for applications. To our knowledge, this is the only DCS IPDA calibration demonstration to date.

Carbon dioxide hydrate formation in porous media under dynamic conditions

AbstractInjecting carbon dioxide (CO2) into subsea water zones where the in situ temperatures are below the hydrate‐forming temperature of CO2 has been recently proposed to lock CO2 inside the water zones in solid hydrate form. It is a common concern that CO2 may form hydrates during the injection period that will reduce well injectivity. CO2 injection into sandstone cores under simulated subsea temperatures of 2°C and 3°C was investigated in this study. Experimental result shows that, at 2°C temperature, flowing CO2 at Darcy velocity 0.033 cm/s begins to form hydrate in the sandstone core at about 3.06 MPa (450 psi), which is much higher than the minimum required pressure of 1.5 MPa (220 psi) for CO2 to form hydrate in static condition. The pressure ratio is 450/220 = 2.05. At 3°C temperature, flowing CO2 at Darcy velocity 0.045 cm/s begins to form hydrate in sandstone core at about 3.67 MPa (540 psi), which is much higher than the minimum required pressure of 1.87 MPa (275 psi) for CO2 to form hydrate in static conditions. The pressure ratio is 540/275 = 1.96. The reason why the required minimum pressure for CO2 to form hydrates in dynamic conditions is about double the required hydrate‐forming pressure in static conditions is not fully understood. It is speculated that the shear rate effect of flowing fluids should slow down the growth of hydrate crystals or break down hydrate films, resulting in delayed formation of bulk CO2 hydrates. More investigations in this area are needed in the future.

Comparison of low-pressure and standard-pressure pneumoperitoneum laparoscopic cholecystectomy in patients with cardiopulmonary comorbidities: a double blinded randomized clinical trial

BackgroundThe benefits of low-pressure laparoscopic cholecystectomy (LPLC) in patients with cardiopulmonary comorbidities remain unclear. This study aimed to explore the feasibility and pulmonary effects of LPLC in patients with cardiopulmonary comorbidities.MethodsThis was a multicenter, parallel, double-blind, randomized controlled trial. Eligible patients included patients with cardiac or pulmonary comorbidities, who were randomly assigned (1:1) to undergo LPLC (10 mmHg) or standard-pressure laparoscopic cholecystectomy (SPLC) (14 mmHg). The primary outcome was postoperative partial pressure of carbon dioxide (CO2). Surgical safety variables, patient recovery, pulmonary function parameters, and surgeon comfort were also compared between groups.ResultsThis study enrolled 144 participants, with 124 participants extracted for the final analysis (62 in LPLC and 62 in SPLC group, respectively). The median postoperative PaCO2 was similar in the LPLC (43.3 mmHg) and SPLC (43.0 mmHg) groups (p = 0.988). Pulmonary parameters including postoperative pH, PaCO2, HCO3, and lactate levels were similar between the two groups. Postoperative base excess was significantly higher in the LPLC group (− 0.6 mmol/L [− 6.9 ~ 7.5] vs. −1.9 mmol/L [− 6.6 ~ 5.4]; p = 0.031). There was no between-group difference regarding intraabdominal operative time, rate of intraoperative bile spillage, blood loss, surgeon comfort during surgery, and conversion rate. Moreover, postoperative major complication rates, the median time to the first flatus, postoperative hospital stay, or mean postoperative visual analog scale score for pain were similar in both groups.ConclusionsThis study found no reduction of partial pressure of CO2 with LPLC compared with SPLC for patients with cardiopulmonary comorbidities. LPLC with a pneumoperitoneum pressure of 10 mmHg may be safe and feasible for these patients when performed by experienced surgeons, although it does not improve pulmonary parameters.RegistrationThe trial is retrospectively registered at ClinicalTrials.gov (NCT04670952) on December 17, 2020.

Dependence of cyanobacterium growth and Mars-specific photobioreactor mass on total pressure, pN2 and pCO2

In situ resource utilization systems based on cyanobacteria could support the sustainability of crewed missions to Mars. However, their resource-efficiency will depend on the extent to which gases from the Martian atmosphere must be processed to support cyanobacterial growth. The main purpose of the present work is to help assess this extent. We therefore start with investigating the impact of changes in atmospheric conditions on the photoautotrophic, diazotrophic growth of the cyanobacterium Anabaena sp. PCC 7938. We show that lowering atmospheric pressure from 1 bar down to 80 hPa, without changing the partial pressures of metabolizable gases, does not reduce growth rates. We also provide equations, analogous to Monod’s, that describe the dependence of growth rates on the partial pressures of CO2 and N2. We then outline the relationships between atmospheric pressure and composition, the minimal mass of a photobioreactor’s outer walls (which is dependent on the inner-outer pressure difference), and growth rates. Relying on these relationships, we demonstrate that the structural mass of a photobioreactor can be decreased – without affecting cyanobacterial productivity – by reducing the inner gas pressure. We argue, however, that this reduction would be small next to the equivalent system mass of the cultivation system. A greater impact on resource-efficiency could come from the selection of atmospheric conditions which minimize gas processing requirements while adequately supporting cyanobacterial growth. The data and equations we provide can help identify these conditions.

CO2-assisted gasification of Patagonian rosehip bio-wastes: Kinetic modeling, analysis of ash catalytic effects, and product gas speciation

In the present study, the valorization of two rosehip wastes –husk and seed– was performed, through the CO2 gasification of biochar obtained by pyrolysis. The kinetics of gasification in a CO2 atmosphere at different partial pressures was investigated, obtaining the activation energy (E), pre-exponential factor (A), conversion function (f(α)), and reaction order with respect to the partial pressure of CO2 (x). The rosehip seed waste biochar (RSWB) yielded the following parameters: E = 302.11 kJ/mol, A = 2.18×1012 1/(s atm0.64), f(α) = 321−α−1/3−1−1; while the rosehip husk waste biochar (RHWB) results were: E = 198.60 kJ/mol, A = 2.13 × 1008 1/(s atm0.64), f(α) = 21−α1/2. The reaction order was the same in both wastes and equal to 0.64. The greater reactivity of RHWB can be attributed to the catalytic effects of the ashes contained in the biomass. To evaluate this effect, tests were conducted on rosehip husk waste ash mixtures with orthoasphaltite mineral char in proportions of 1, 5, 7, and 10 % (m/m). Thermogravimetry determined that the gasification temperature decreased up to 200 °C compared to pure char. Additionally, dry gasification of raw biomass experiments were carried out, and the evolution of gaseous products was analyzed with FTIR spectroscopy, evaluating the absorbance profiles of CO, CH4, and CH3OH, and comparing them with those obtained in a pure N2 atmosphere. The results obtained demonstrated the potential of rosehip wastes as a source in thermochemical processes for its complete valorization in a production chain with a focus on biorefinery.

Seasonal variation of CO2 air-sea flux and effects of warming in the Kuroshio current of the East China Sea

The partial pressure of CO2 (pCO2) and associated CO2 air-sea flux exhibit highly heterogeneous temporal and spatial patterns in ocean margins. In this study, we analyzed a three-year time-series data sampled during 2011–2014 along the Kuroshio Current within the East China Sea (ECS) to investigate the seasonal pattern of carbonate chemistry and CO2 air-sea fluxes. Annually, the Kuroshio within the ECS operates as a net CO2 sink at approximately 1.3 mol C m−2 yr−1, less than estimates over the ECS shelf (~1.8 mol C m−2 yr−1). The thermal control of pCO2 makes the Kuroshio a strong CO2 sink in winter, with a transition to net-neutral, or a weak CO2 source in summer. On an interannual basis, however, the seasonal CO2 air-sea fluxes in the Kuroshio may undergo potential shifts if warming conditions continue.

A novel approach to accelerate the carbonation of γ-C2S under atmospheric pressure: Increasing CO2 dissolution and promoting calcium ion leaching via triethanolamine

An innovative approach to accelerate the carbonation of the γ-2CaO·SiO2 (γ-C2S) under atmospheric pressure was proposed by incorporating triethanolamine (TEA). The effect of TEA on the degree of carbonation (DOC) and the mechanical strength of γ-C2S were investigated, and the mechanism of carbonation accelerated by TEA under atmospheric pressure was analyzed. The results showed that as TEA concentration increased from 0.1 % to 5 %, the DOC initially increased and then decreased, with an optimal concentration of 1 %, where the DOC increased by 126.6 % compared to reference samples after 1 d of carbonation under atmospheric pressure, and this DOC was slightly higher than that of carbonated pastes without TEA under a CO2 pressure of 0.4 MPa. For γ-C2S mortar specimens, the flexural strength and compressive strength with 1 % TEA increased by 109.8 % and 99.3 %, respectively, and these values were slightly higher than those of specimens without TEA under CO2 carbonation pressure of 0.4 MPa. Additionally, at the optimal TEA concentration, CO2 solubility increased by 10.8 times and Ca2+ concentration increased by 94.7 %. This dual effect led to the carbonation rate under atmospheric pressure that could match or slightly exceed that under CO2 pressure of 0.4 MPa, which made this method a novel technique for accelerating carbonation.

A robust floating oxygen-doped graphitic carbon nitride sheet for efficient photocatalytic CO2 conversion

Photocatalytic CO2 reduction offers a promising approach for converting CO2 into valuable chemicals. However, typical conversion systems suffer from inefficient CO2 mass transfer and complex recycling processes. In this study, we developed a floating sheet as a robust photocatalytic CO2 conversion system by integrating graphitic carbon nitride (CN) nanosheets onto polytetrafluoroethylene (PTFE) fiber membrane, followed by oxygen (O) doping into the CN (CN-O) via oxygen-plasma treatment. The floatable CN-O/PTFE sheet exhibits slight wettability in water under 0.25 MPa of CO2 pressure in our reactor system, facilitating the delivery of dissolved CO2 to the CN-O photocatalyst surface. O-doping enhances the visible light absorption and improves the separation and transport efficiency of photogenerated electrons and holes due to O-doping-induced states in CN. Consequently, the floating CN-O/PTFE system achieves an exceptional photocatalytic CO2 conversion rate of 102.3 μmol g-1h−1, approximately 4.8 times higher than a conventional CN-powder dispersion system in water. Moreover, the sheet demonstrates excellent cycling durability, with no significant exfoliation of the catalytic layer or reduction in CO2 photoreduction activity after 20 consecutive cycles. This study presents a novel approach to designing photocatalytic systems for efficient CO2 conversion.

Aerated Concrete Made of MSW Incineration Ash: Effect of Blending Materials and CO2 Curing Condition

Municipal solid waste (MSW) incineration ash is used to produce aerated concrete blocks (ACB). To reduce cement usage and improve ACB quality, steel slag and blast-furnace slag were tested as cement substitutes, and CO2 mineralization technology was applied to cure ACB. The effect of steel blending ratios (MSW incineration ash, cement substitutes, water, aluminum powder) and CO2 curing conditions (temperature, pressure) on ACB properties was investigated. Under different conditions, the compressive strength, CO2 uptake and microstructure of ACB were determined. Higher fly ash content in ACB increases CO2 uptake but reduces compressive strength; ACB shows better mechanical properties when the cement is completely replaced by blast-furnace slag, but steel slag will cause ACB to fail to form; the optimal water-to-solid ratio enhances carbonation rate and compressive strength, and reducing aluminum powder content improves compressive strength. As the CO2 curing temperature increases from 25 to 105ºC, the carbonation rate and compressive strength of the ACB initially increase and then decrease, with the maximum CO2 uptake ratio of 20.0% and peak compressive strength occurring at 65ºC. When CO2 pressure increases from 0.2MPa to 1MPa, the carbonation rate rises to 23.4%, and the compressive strength first increases and then decreases, reaching 1.86MPa at a curing pressure of 0.6MPa, meeting the GB/T 11968-2020 B03 A1.5 grade standard. Approximately 0.58 tons of CO2 emissions can be reduced for every ton of ACB produced. This study established an innovative method to produce an environmentally friendly, low-carbon building material.

Experimental and kinetic study of pressurized CO2 gasification of biomass chars

Experimental and kinetic study of pressurized CO2 gasification of biomass chars

Green solvents assisted de-novo synthesis and defect-engineered UiO-66 for improved CO2 adsorption and kinetics- experimental and DFT approach

The CO2 concentration in the atmosphere is increasing at an alarming rate, which is causing distress to human society and the natural environment. Adsorption is one of the most widely used methods of removing CO2 from flue gases, which reduces its adverse effects on our environment. For adsorption purposes, a facile green solvent-assisted de-novo synthesis approach was developed to construct a UiO-66′s structure to target CO2 at low pressure due to the partial pressure of CO2 in flue gases in the atmosphere (0.01⁓0.02 MPa). In the de-novo synthesis approach, a combination of various types of modulators and deep eutectic solvents (DES) are utilized to graft structural defects and induce quantitative and dispersive deep eutectic solvents onto the UiO-66 structure, respectively. The green solvent-assisted de-novo synthesis approach helped to tune all three structural parameters and preserve extra open metal sites (Lewis acid and Bronsted basis sites) with active NH2 and OH groups for improved CO2 adsorption and kinetics under flue gas conditions (CO2/N2=15/85 %). In comparison to the parent UiO-66, de-novo synthesized ChClPropx5@UiO-66 showed increased CO2 uptake (65.04 mg g-1) by 73 % at 0.15 bar and 25 °C, and the cyclic capacity remained almost similar over 10 consecutive cycles with an almost 94 % retention rate. After 3 times of regeneration at 105 °C under N2 atmosphere, the sample reserved almost similar adsorption capacity and could be recycled without dropping CO2 uptake. The strong and rapid interaction between guest CO2 and de-novo synthesized UiO-66 was confirmed by pseudo-first-order and second-order kinetics with reaction rate constants of 0.00026 and 0.00259, respectively. Furthermore, through periodic Density Functional Theory (DFT) calculations, a variety of linker defects are engineered onto the UiO-66 structure to preserve more open metal sites. For each of the engineering defects, free energies, adsorption energies, and the interaction of CO2 molecules on defect structures with bond length (Ɩ, Å) and bond angle (θ˚) are calculated for the most stable structures of UiO-66.

Two Sustainable Pathways of MOF-Catalyzed Room Temperature Chemical Fixation of CO2 inside Alkynes under Atmospheric Pressure.

The rising atmospheric CO2 levels necessitate the development of effective materials for its mitigation. Utilization of adsorbent materials for the reversible physisorption of CO2 has a significantly less impact. Recognizing this need, herein, we present a nitrogen-rich, aqua-stable, Ag(0)-nanoparticle-doped metal-organic framework (MOF) designed for the irreversible chemical conversion of CO2 into valuable fine chemicals. We demonstrate two sustainable pathways for CO2 fixation, utilizing the catalyst, 1'@Ag NPs. The designed catalyst facilitates the cyclization of propargylic amines and alcohols under ambient temperature and pressure conditions. Remarkably, this is the first MOF-based catalyst that allows for quantitative conversion of propargylic amines into 2-oxazolidinones at room temperature with atmospheric CO2 pressure. The process successfully transforms various propargylic amines and alcohols into 2-oxazolidinones and α-alkylidene cyclic carbonates under the CO2 atmosphere. Additionally, the catalyst shows excellent recyclability, maintaining its activity and structural integrity across multiple reuse cycles. Control experiments revealed that the catalytic efficiency of 1'@Ag NPs is attributed to the highly exposed alkynophilic Ag(0) sites on its pore walls. Computational studies further elucidate the mechanistic pathway for CO2 fixation. This work highlights the potential of 1'@Ag NPs to enhance environmental sustainability by converting CO2 into valuable bioactive chemicals under mild conditions.

Distribution and air-sea fluxes of CO2 in coral reefs in the Greater Bay Area, China

From May to June 2021, the sea surface partial pressure of CO2 (pCO2) and air-sea CO2 fluxes around six coral reefs in the Great Bay Area (contain Pearl River Estuary (PRE) and Daya Bay) were investigated respectively. The distribution of seawater pCO2 around different coral reefs were quite different. The seawater pCO2 of the coral reef region of Daya Bay is relatively high, ranging from 268 to 496 µatm. In contrast, the pCO2 levels in the coral reef area of the PRE are significantly lower, with measurements ranging from 84 to 374 µatm. Further analysis showed that the distribution of seawater pCO2 around the coral reefs of the PRE were mainly affected by biological metabolism and seawater mixing, while those in Daya Bay were mainly controlled by temperature and seawater mixing. During the survey, the three coral reefs in the PRE were affected by algal blooms showing strong sinks of atmospheric CO2 ranging from −12.3 to −19.2 mmol CO2 m−2 d−1. However, the difference between the seawater pCO2 and atmospheric pCO2 in the three coral reefs of Daya Bay were all very small, and they were weak sources or sinks of atmospheric CO2, respectively.