Manipulating the size,the morphology and the polymorphism of acetaminophen using supercritical antisolvent (SAS) precipitation

The supercritical antisolvent technology is used to crystallize paracetamol particles. Supercritical carbon dioxide (scCO₂) is used as antisolvent. Ethanol, acetone and mixtures of ethanol and acetone are used as solvents. The initial concentration of paracetamol in the solution was varied between 1 and 5 wt%, the composition of the ethanol/acetone solvent mixture between 50 and 90 wt% of ethanol and the operation pressure between 10 and 16 MPa at a temperature of 313 K. The most important finding is that the polymorph of paracetamol crystals can be adjusted between monoclinic and orthorhombic by varying the content of ethanol in the solution. The second important finding is that the occurrence of primary and secondary crystal structures can be explained solely by the overall supersaturation during the crystallization process. While X-ray diffraction was used to analyze the polymorph of the particles, their morphology was analyzed using scanning electron microscopy.     

Naproxen–nicotinamide cocrystals produced by CO2 antisolvent

Cocrystals of naproxen (NPX) and nicotinamide (NCTA) were successfully prepared in acetone using CO₂ as antisolvent in the so-called GAS technique (Gaseous Anti Solvent). Infra-red spectroscopy and powder X-ray analysis evidenced the same hydrogen-bond network and stoichiometry than cocrystals produced by cooling crystallization, i.e. 2 NPX for 1 NCTA, which coincided with literature results as well. The purity of powders in cocrystals was evaluated thanks to chromatography analysis and the homocrystals identification by powder X-rays diffraction. The effect of initial mixture composition (NPX:NCTA ratio) and of CO₂ and acetone mixing conditions (CO₂ introduction rate, stirring speed) was investigated. Results showed that the cocrystal purity was closed to 98 ± 2% whatever the initial ratio in solution of 3:1, 2:1, 1:1 but levelled down to 67% when a 1:2 solution was processed. The mixing conditions did not influence the cocrystal stoichiometry or purity (experiments carried out from a 2:1 mixture) but impacted on precipitation yield and size distribution. In best conditions, 62% of the initial processed amount was collected in the vessel as a powder of sizes below 180 μm made at 98% of NPX₂:NCTA₁ cocrystals.     

Laser analyses of mixture formation and the influence of solute on particle precipitation in the SAS process

Laser based Raman and elastic light scattering measurements were performed to study the process of mixture formation and the influence of the solute paracetamol onto the phase behaviour of the pseudo-binary system ethanol/CO₂ in the supercritical antisolvent process. From the Raman based technique, mole fraction and partial density distributions of CO₂ were obtained. The mole fraction distributions indicate a rapid mixture formation with fast supersaturation of the solute. At the same time, the increase of the CO₂ partial density at conditions considerably above the mixture critical point (MCP) indicate a change from a homogeneous supercritical to a multi-phase subcritical flow. This phase change goes along with particle precipitation. Thus, the results of our investigations proof, why past approaches failed to generate amorphous paracetamol nanoparticles with the system paracetamol/ethanol/CO₂ above the MCP. Process parameters like injection pressure (20.0–35.0 MPa), chamber pressure of CO₂ (7.5–17.5 MPa), temperature (313–333 K) and solute concentration (0–5 wt%) were varied.     

Lycopene solubility in mixtures of carbon dioxide and ethyl acetate

In order to improve the efficiency of processes using supercritical (sc) carbon dioxide (CO₂) to micronize the carotenoid “lycopene”, it is important to know the solubility of lycopene in mixtures of the organic solvent ethyl acetate (EA) and the antisolvent CO₂ at elevated pressures. The solubility of lycopene has been determined for different temperatures (313–333 K), pressures (12–16 MPa) and CO₂ molar fractions (0.58–1). The obtained data show that CO₂ acts as an antisolvent in the system lycopene/EA/CO₂ in the range of CO₂/EA ratios studied. The solubility of lycopene is rather small with lycopene molar fractions ranging from 0.1 × 10⁻⁶ to 46 × 10⁻⁶. The solubility of lycopene increases with temperature, pressure and EA concentration.     

High-pressure phase equilibrium measurements and thermodynamic modeling for the systems involving CO2, ethyl esters (oleate,stearate, palmitate) and acetone

The aim of this work was to study the phase behavior of systems involving carbon dioxide (CO₂), fatty acid ethyl esters (ethyl oleate, ethyl stearate and ethyl palmitate) and acetone at high pressures. The phase behavior involving these components is an important step regarding the design and optimization of industrial processes based on supercritical conditions, such as biodiesel production and fatty esters fractionation involving supercritical and/or pressurized solvents. In addition, supercritical CO₂ can offer an interesting alternative for glycerol separation in water-free biodiesel purification processes. The binary systems investigated in this work were CO₂ + ethyl oleate, and CO₂ + ethyl stearate and these were compared with the CO₂ + ethyl palmitate system. The ternary CO₂ + ethyl palmitate + acetone was also investigated at two different ethyl palmitate to acetone molar ratios of (1:1) and (1:3). The static synthetic method using a variable-volume view cell was employed to obtain the experimental data in the temperature range of 303.15–353.15 K. Vapor–liquid (VL), liquid–liquid (LL) and vapor–liquid–liquid (VLL) phase transitions were observed in these systems. In the binary systems, the solubility increased with the presence of unsaturation and decreased with the number of carbon atoms in the fatty ester chain. Addition of acetone as well as ethanol eliminated the liquid–liquid immiscibility and reduced the pressure transitions, therefore increasing the solubility of the ester in supercritical CO₂. The experimental data sets for the binary and ternary systems were successfully modeled using the Peng–Robinson equation of state with the classical van der Waals quadratic mixing rule (PR-vdW2) and Wong-Sandler (PR-WS) mixing rule. Both models showed good performance in the phase equilibrium correlations and in predictions for the binary and ternary systems.     

Determination of crystal growth rate for porcine insulin crystallization with CO2 as a volatile acidifying agent

Crystallization is controlled by two steps that determine the quality and the final size of the product, nucleation and growth, which are functions of supersaturation. Recently, Hirata et al. [1] crystallized insulin using CO₂ as a volatile acid to impose supersaturation on the system. The objective of the present work was to determine the growth kinetics of insulin crystallization in 50 mM NaHCO₃ solution with 0.4 mM ZnCl₂ in a CO₂ atmosphere at 15 °C, adjusting the parameters of the equation G = k_g × S^g to the experimental data. The solubility of insulin in the NaHCO₃/CO₂/ZnCl₂ system at 15 °C was determined as a function of pH in the range of 6.30–7.34. The crystal growth data allowed determination of the growth order “g” (g = 2.9). Although protein crystallization has some features that differ from the crystallization of less complex molecules, the apparent growth kinetics of insulin were successfully analyzed here with the same empirical methods used for small molecules, which can easily be scaled up for industrial applications to achieve specific size and purity, the goals of industrial crystallization. The method used in this work is a useful tool for describing and simplifying optimization of industrial protein crystallization processes.     

Interactions of phase equilibria,jet fluid dynamics and mass transfer during supercritical antisolvent micronization

Supercritical antisolvent (SAS) precipitation has been successfully used in the micronization of several compounds. Nevertheless, the role of high-pressure vapor–liquid equilibria, jet fluid dynamics and mass transfer in determining particle size and morphology is still debated. In this work, CO₂ has been adopted as supercritical antisolvent and elastic light has been used to acquire information on jet fluid dynamics using thin wall injectors for the investigation of the liquid solvents acetone and DMSO at operating conditions of 40 °C in the pressure range between 6 and 16 MPa. The results show that two-phase mixing after jet break-up is the phenomenon that characterizes the jet fluid dynamics at subcritical conditions. When SAS is performed at supercritical conditions a transition between multi-phase and single-phase mixing is observed by increasing the operating pressure. Single-phase mixing is due to the very fast disappearance of the interfacial tension between the liquid solvent and the fluid phase in the precipitator. The transition between these two phenomena depends on the operating pressure, but also on the viscosity and the surface tension of the solvent. Indeed, single-phase mixing has been observed for acetone very near the mixture critical point, whereas DMSO showed a progressive transition for pressures of about 12 MPa.In the second part of the work, a solute was added to DMSO to study the morphology of the microparticles formed during SAS precipitation at the different process conditions, to find a correlation between particle morphology and the observed jet. Expanded microparticles were obtained working at subcritical conditions; whereas spherical microparticles were obtained operating at supercritical conditions up to the pressure where the transition between multi- and single-phase mixing was observed. Nanoparticles were obtained operating far above the mixture critical pressure. The observed particle morphologies have been explained considering the interplay among high-pressure phase equilibria, fluid dynamics and mass transfer during the precipitation process.     

Solubility and diffusion coefficient of supercritical-CO2 in polycarbonate and CO2 induced crystallization of polycarbonate

The solubility and diffusion coefficient of supercritical CO₂ in polycarbonate (PC) were measured using a magnetic suspension balance at sorption temperatures that ranged from 75 to 175 °C and at sorption pressures as high as 20 MPa. Above certain threshold pressures, the solubility of CO₂ decreased with time after showing a maximum value at a constant sorption temperature and pressure. This phenomenon indicated the crystallization of PC due to the plasticization effect of dissolved CO₂. A thorough investigation into the dependence of sorption temperature and pressure on the crystallinity of PC showed that the crystallization of PC occurred when the difference between the sorption temperature and the depressed glass transition temperature exceeded 40 °C (T − T_g ≥ 40 °C). Furthermore, the crystallization rate of PC was determined according to Avrami's equation. The crystallization rate increased with the sorption pressure and was at its maximum at a certain temperature under a constant pressure.     

Supercritical antisolvent micronization of PVP and ibuprofen sodium towards tailored solid dispersions

The supercritical antisolvent technology is used to precipitate polyvinylpyrrolidone (PVP) particles and crystallise ibuprofen sodium (IS) crystals separately and in the form of solid dispersion together. Supercritical carbon dioxide (scCO₂) is used as antisolvent. For PVP particle generation, ethanol, acetone and mixtures of ethanol and acetone are used as solvents. The initial concentration of PVP in the solution was varied between 0.5 wt% and 1.5 wt%, the operation pressure between 10 MPa and 30 MPa and the composition of ethanol/acetone solvent mixtures between 100 wt% and 0 wt% of ethanol at a constant temperature of 313 K. Furthermore, the mean molecular weight of the polymer was varied between 40 kg mol⁻¹, 360 kg mol⁻¹ and 1300 kg mol⁻¹. An increase of the content of the poor solvent acetone in the initial solvent mixture as well as the usage of PVP with a higher molecular weight, leads to a significant decrease in mean particle size. At all the investigated parameters always fully amorphous PVP powder precipitates. For IS, only ethanol was used as the solvent, the initial IS concentration in the solution was varied between 1 wt% and 3 wt% and the operation pressure between 10 MPa and 16 MPa. A variation of these parameters leads to a manipulation of the size and the morphology of the crystallised IS crystals. Irrespective of the parameters used, always the same polymorphic form of ibuprofen sodium is produced. The solid dispersions were generated at different compositions of PVP to IS and with two different molecular weights of PVP at otherwise constant conditions. Fully amorphous solid dispersions consisting of IS and PVP together were generated at different ratios of PVP to IS.The mechanisms that control the final particle properties are discussed taking into account two different models for “ideal” and “non-ideal” solutes. Furthermore, the study of the “unconventional” SAS parameters, molecular weight and solvation power of the solvent shows that these parameters qualify to tailor polymer particle properties via SAS processing. Next to the investigation into the behaviour of both solutes separately, fully amorphous solid dispersions consisting of IS and PVP together were generated. While X-ray diffraction was used to analyze the crystalline structure of the particles, respectively, solid dispersions, their morphology was analysed using scanning electron microscopy (SEM).     

Phase equilibria for the 2-ethoxyethyl acetate and 2-(2-ethoxyethoxy)ethyl acetate in supercritical CO2 at various temperatures and pressures up to 20 MPa

The (CO₂ + 2-ethoxyethyl acetate) and (CO₂ + 2-(2-ethoxyethoxy)ethyl acetate) systems at 313.2, 333.2, 353.2, 373.2 and 393.2 K as well as pressures up to 20.59 MPa have been investigated using variable-volume high pressure view cell by static-type. The solubility curve of 2-ethoxyethyl acetate and 2-(2-ethoxyethoxy)ethyl acetate in the (CO₂ + 2-ethoxyethyl acetate) and (CO₂ + 2-(2-ethoxyethoxy)ethyl acetate) systems increases as the temperature increases at a constant pressure. The (CO₂ + 2-ethoxyethyl acetate) and (CO₂ + 2-(2-ethoxyethoxy)ethyl acetate) systems exhibit type-I phase behavior. The experimental results for the (CO₂ + 2-ethoxyethyl acetate) and (CO₂ + 2-(2-ethoxyethoxy)ethyl acetate) systems correlate with the Peng–Robinson equation of state using a van der Waals one-fluid mixing rule including two adjustable parameters. The critical properties of 2-ethoxyethyl acetate and 2-(2-ethoxyethoxy)ethyl acetate are predicted with the Joback–Lyderson group contribution and Lee–Kesler method.     

Density and viscosity of the binary polyethylene glycol/CO2 systems

Density of CO₂ saturated solutions of polyethylene glycols (PEGs) of different molecular weight was measured in pressure range from 8.0 MPa up to 47.7 MPa at a temperature of 343 K by a volumetric method. To validate the method density of pure CO₂ was measured at different pressures and a temperature of 293 K. The results were compared to the literature data and the accuracy was better than 2%. The density was between 1.17 g/mL for PEG 1000/CO₂ at 14.5 MPa and 1.78 g/mL for the system PEG 4000/CO₂ at 35 MPa. Further, the data were compared to results, obtained by a gravimetric method using magnetic suspension balance (MSB).Viscosity of CO₂ saturated solutions of polyethylene glycols (PEGs) of different molecular weight at different pressures and at a temperature of 343 K was measured using a high pressure view cell. Also a temperature impact on the viscosity of pure PEGs was observed at ambient pressure. After saturating PEG 1500 with 10 MPa of CO₂ pressure its viscosity decreases from 76.6 mPa s to 2.24 mPa s at 333 K. Further addition of CO₂ and increasing the pressure results in even lower viscosity and the highest viscosity reduction was reached at the highest pressure; at 35 MPa viscosity of the system PEG 1500/CO₂ is only 0.665 mPa s.     

High pressure densities of carbon dioxide + dipentaerythritol hexaheptanoate: New experimental setup and volumetric behavior

To perform an appropriate selection of the lubricants in air conditioned systems working with carbon dioxide as refrigerant, the thermodynamic behavior of the CO₂ + lubricant systems must be well known. In this work we present a new setup to prepare compressed gas–liquid mixtures and to determine the high pressure density by using an automated densimeter HPM and two syringe pumps. To analyze the reliability of the procedure proposed, we have determined the densities and mixing volumes of four CO₂ + n-decane mixtures. We have found a good agreement with previous literature data. In addition new density values are reported for the binary system CO₂ + dipentaerythritol hexaheptanoate (DiPEC7) at several temperatures and pressures from 10 MPa to 120 MPa.     

Combined high hydrostatic pressure and carbon dioxide inactivation of pectin methylesterase,polyphenol oxidase and peroxidase in feijoa puree

A combined treatment of high hydrostatic pressure (HHP) and dense phase carbon dioxide (DPCD) was investigated to inactivate pectin methylesterase (PME), peroxidase (POD) and polyphenol oxidase (PPO) in feijoa (Acca sellowiana) puree. The treatments were HHP (HHP); carbonation and HHP (HHPcarb); carbonation + addition of 8.5 mL CO₂/g puree into the headspace of the package and HHP (HHPcarb + CO₂). The different samples were treated at 300, 450 and 600 MPa, for 5 min.The residual POD and PPO activity decreased in the order HHP > HHPcarb > HHPcarb + CO₂ at all pressures used. Treatments with HHP at 300 MPa increased POD activity to 140%. The residual PME activity of HHPcarb and HHPcarb + CO₂ samples at 600 MPa (45–50%) was significantly (p < 0.05) lower than for HHP treatment (65%).The simultaneous application of HHP and DPCD seems to synergistically enhance the inactivation of the enzymes studied, the CO₂ concentration being a key process factor.     

Phase equilibrium of two CO2+ biodegradable oil systems up to 72 MPa

A setup based on a static visual synthetic method for determining phase equilibria up to 100 MPa is presented. Solubilities of carbon dioxide (CO₂) in a high-oleic sunflower oil (HOSO) and in an additivated vegetable lubricant (BIO-2T-05) were determined from 298 K to 363 K up to CO₂ mass compositions of 0.42. The experimental device was verified comparing the solubilities of CO₂ in HOSO with values from other laboratory. For both systems, the values of CO₂ solubility show cross-over pressures among the different isotherms. A new equation was used to correlate the solubility data, with deviations in CO₂ mole fraction in the oil-rich phase lower than 1.6%. The prediction ability of Carvalho and Coutinho equation was tested with experimental data. Vapor–liquid–liquid equilibria were also investigated for CO₂ + BIO-2T-05 in the range 288–305 K. Furthermore, densities and viscosities at 0.1 MPa for BIO-2T-05 were measured from 278 K to 373 K.     

Near-infrared spectroscopic solubility measurement for thermodynamic analysis of melting point depressions of biphenyl and naphthalene under high-pressure CO2

Melting temperatures of organic solids are often depressed by high-pressure CO₂ due to a dissolution of CO₂ in the molten organic compounds. For thermodynamic analysis of the melting point depression, solubilities of CO₂ in molten biphenyl and naphthalene were measured by near-infrared spectroscopy at various temperatures and pressures up to 20 MPa. Molarity of the organic component was determined from the 3ν_CH absorption band, and that of CO₂ from the 2ν₁ + ν₃ band. Mole fraction of CO₂ in the liquid phase was found to be an increasing function of the pressure up to 0.6 at 20 MPa and a weakly decreasing function of the temperature. The solubility data were used for modeling of the mixtures by the Peng–Robinson equation of state with a binary interaction parameter k₁₂. Calculation of the solid–liquid–gas phase equilibrium for the model fluid qualitatively described a large decrease in the melting temperature with increasing pressure up to 10 MPa followed by a small change at higher pressures. The melting point change was interpreted by the two competing effects: hydrostatic pressure effect increases the melting point by ca. 8 °C at 20 MPa, whereas CO₂ solubility effect reduces it by ca. 30 °C. Decomposition of the solubility effect into ideal and non-ideal mixing parts revealed that the non-ideality increases the melting point by more than 10 °C.     

Phase equilibria of the propylene glycol/CO2 and propylene glycol/ethanol/CO2 systems

The high-pressure vapour–liquid phase equilibria (P–T–x–y) of the binary mixture propylene glycol/CO₂ have been experimentally investigated at temperatures of (398.2, 423.2 and 453.2) K over the pressure range from (2.5 to 55.0) MPa using a static-analytic method. Furthermore, the high-pressure vapour–liquid phase equilibria (P–T–x–y) of the ternary mixture propylene glycol/CO₂/ethanol at constant temperatures of (398.2, 423.2 and 453.2) K and at constant pressure of 15.0 MPa have been determined using a static-analytic method. Initial concentrations of components in propylene glycol (PG)/ethanol (EtOH) mixture vary from 10 up to 90 wt.%. In general, for binary system it was observed that the solubility of CO₂ in the heavy propylene glycol reach phase increases with increasing pressure at constant temperature. On the contrary, the composition of gaseous phase is not influenced by the pressure or the temperature. On average the solubility of PG in light phase of CO₂ amounts to 30 wt.%. The system behaviour at temperature of 398.2 K was investigated up to 70.0 MPa and a single-phase region was not observed. Above the pressure 60.0 MPa a single-phase region of the system was observed for the temperature of 423.2 K. For the temperature of 453.2 K the single-phase was observed above the pressure of 48.0 MPa. For ternary system it was observed that the composition of heavy phase is slightly influenced by the temperature when the mass fraction of EtOH in initial mixture is higher than 50 wt.%. If the mass fraction of PG in initial mixture is higher than 50 wt.%, the composition of heavy phase is not influenced by the temperature anymore. The composition of the PG, EtOH and CO₂ in light phase remains more or less unchanged and it is not influenced by the conditions.     

Ovicidal activities of supercritical CO2 and N2O on Ascaris suum eggs

This study examined whether supercritical CO₂ and N₂O fluids are effective in inactivating Ascaris suum eggs, which were chosen as a model for parasite eggs. The treatments were carried out in a multibatch apparatus, in which, the eggs could be placed atop a solid surface (non-immersed condition) or in aqueous solution (immersed condition). Various CO₂ and N₂O phases—including gas (6 MPa, 30 °C), liquid (8 MPa, 30 °C), subcritical (10 MPa, 30 °C), and supercritical (10 MPa, 37 °C)—were tested with exposure times ranging from 1 to 20 min. Supercritical CO₂ and N₂O both showed a similar, strong ovicidal effect, requiring only 1 min in non-immersed conditions and 5 min in water-immersed conditions to achieve a 2.4-log inactivation. Subcritical CO₂ and N₂O showed a weaker ovicidal effect. The effect was significantly reduced for the gas and liquid phases, compared with the supercritical phases. This study reports that supercritical CO₂ and N₂O can be effectively employed as a non-thermal treatment technique to control parasite egg contamination in fecal matter and food.     

Generation and precipitation of paclitaxel nanoparticles in basil seed mucilage via combination of supercritical gas antisolvent and phase inversion techniques

In recent years, plant derived polymers have evoked tremendous interest in the field of drug delivery. In this work, a promising anticancer drug, paclitaxel, was precipitated in the basil seeds mucilage (BSM) using supercritical carbon dioxide (SC-CO₂). The employed SC-CO₂ process in this research is a combination of gas antisolvent and phase inversion techniques and consists of two steps: (1) casting solution preparation, a uniform mixture of BSM, water, paclitaxel and dimethyl sulfoxide (DMSO), (2) simultaneous generation and precipitation of nanoparticles in BSM structure using SC-CO₂ as antisolvent. The effect of DMSO/water ratio (4 and 6 (v/v)), pressure (10–16 MPa) and CO₂ addition rate (1–3 mL/min) on mean particle size (MPS), particle size distribution (PSD) and drug loading efficiency (DLE) were studied. Particle analyses were performed by scanning electron microscopy (SEM) and Zetasizer. High performance liquid chromatography was utilized for studying DLE. Nanoparticles of paclitaxel (MPS of 117–200 nm depending on process variables) with narrow PSD were successfully precipitated in BSM structure with DLE of 56.8–78.2%. The FTIR spectra confirmed that paclitaxel actually precipitated in basil seeds mucilage. Experimental results indicated that higher DMSO/water ratio, pressure and CO₂ addition decreased MPS and DLE.     

Use of solvent mixtures in supercritical antisolvent process to modify precipitates morphology: Cellulose acetate microparticles

In the supercritical antisolvent precipitation (SAS), the jet fluid dynamics is characterized by two-phase mixing at subcritical conditions, and by one-phase mixing at completely developed supercritical conditions. The amplitude of the pressure range, in which binary systems organic solvent/scCO₂ exhibit the transition between two-phase to one-phase mixing, depends on the organic solvent that is in contact with supercritical carbon dioxide (scCO₂) and conditions the morphology of the microparticles produced by SAS. When this pressure range is wide, as in the case of dimethylsulfoxide (DMSO), solutes solubilized in the organic solvent can be precipitated as microparticles by atomization, droplets formation and drying; when this pressure range is narrow, as for acetone, gas mixing prevails and only nanoparticles are generally observed. Therefore, generally speaking, solutes that are soluble only in solvents exhibiting gas mixing in scCO₂, do not exhibit microparticles morphology and this fact is a limitation for several industrial applications.In this work, a model compound, cellulose acetate (CA), that is slightly soluble in DMSO and freely soluble in acetone, was processed by SAS using mixtures of the two solvents that exhibit intermediate behaviors between the two pure solvents, to extend two phase mixing and produce CA microparticles. Using different DMSO/acetone mixture percentages, the effects of the polymer concentration in the liquid solution and of the pressure were studied. A mixture of DMSO/Acetone 50/50 (v/v), at a pressure of 85 bar and a concentration of the liquid solution equal to 40 mg/mL, efficiently produced non-coalescing CA microparticles with a mean diameter of 0.42 μm and a standard deviation of about 0.15 μm, demonstrating that this SAS strategy can be successful.     

Effect of the porous structure in carbon materials for CO2 capture at atmospheric and high-pressure

Activated carbons prepared from petroleum pitch and using KOH as activating agent exhibit an excellent behavior in CO₂ capture both at atmospheric (∼168 mg CO₂/g at 298 K) and high pressure (∼1500 mg CO₂/g at 298 K and 4.5 MPa). However, an exhaustive evaluation of the adsorption process shows that the optimum carbon structure, in terms of adsorption capacity, depends on the final application. Whereas narrow micropores (pores below 0.6 nm) govern the sorption behavior at 0.1 MPa, large micropores/small mesopores (pores below 2.0–3.0 nm) govern the sorption behavior at high pressure (4.5 MPa). Consequently, an optimum sorbent exhibiting a high working capacity for high pressure applications, e.g., pressure-swing adsorption units, will require a poorly-developed narrow microporous structure together with a highly-developed wide microporous and small mesoporous network. The appropriate design of the preparation conditions gives rise to carbon materials with an extremely high delivery capacity ∼1388 mg CO₂/g between 4.5 MPa and 0.1 MPa. Consequently, this study provides guidelines for the design of carbon materials with an improved ability to remove carbon dioxide from the environment at atmospheric and high pressure.