Hydrophobic Porous Polyketimines for the Capture of CO2

Porous Structural Properties of K or Na-Co Hexacyanoferrates as Efficient Materials for CO2 Capture

The stoichiometry of the components of hexacyanoferrate materials affecting their final porosity properties and applications in CO₂ capture is an issue that is rarely studied. In this work, the effect that stoichiometry of all element components and oxidation states of transition metals has on the structures of mesoporous K or Na-cobalt hexacyanoferrates (CoHCFs) and CO₂ removal is reported. A series of CoHCFs model systems are synthesized using the co-precipitation method with varying amounts of Co ions. CoHCFs are characterized by N₂ adsorption, TGA, FTIR-ATR, XRD, and XPS. N₂ adsorption results reveal a more developed external surface area (72.69-172.18 m²/g) generated in samples containing mixtures of K⁺/Fe²⁺/Fe³⁺ ions (system III) compared to samples with Na⁺/Fe²⁺ ions (systems I, II). TGA results show that the porous structure of CoHCFs is affected by Fe and Co ions oxidation states, the number of water molecules, and alkali ions. The formation of two crystalline cells (FCC and triclinic) is confirmed by XRD results. Fe and Co oxidation states are authenticated by XPS and allow for the confirmation of charges involved in the stabilization of CoCHFs. CO₂ removal capacities (3.04 mmol/g) are comparable with other materials reported. CO₂ adsorption kinetics is fast (3-6 s), making CoHCFs attractive for continuous operations. Q_st (24.3 kJ/mol) reveals a physical adsorption process. Regeneration effectiveness for adsorption/desorption cycles indicates ~1.6% loss and selectivity (~47) for gas mixtures (CO₂:N₂ = 15:85). The results of this study demonstrate that the CoHCFs have practical implications in the potential use of CO₂ capture and flue gas separations.

Micro- and Ultramicroporous Polyaminals for Highly Efficient Adsorption/Separation of C1-C3 Hydrocarbons and CO2 in Natural Gas

This paper presents a series of micro- and ultramicroporous polyaminals with BET surface areas up to 1304 m² g^-1, which are prepared from two triazine-based tetraamines and three dialdehydes or monoaldehyde through the A₄ + B₂ or A₄ + B₁ aminalization reaction. It is interesting to find that the para-substituted monomers are favorable to force the linking struts apart in the network to generate micropores (1.22 nm), whereas the meta-substituted monomers make the pores in the network squeezed by the twisted linking struts, resulting in the formation of ultramicropores (0.52 nm). Besides, the adsorption behaviors of the major components of natural gas, such as propane (C₃H₈), ethane (C₂H₆), methane (CH₄), and carbon dioxide (CO₂), are significantly different, strongly depending on the polarizabilities, critical temperatures, molecular sizes of gases, porosity parameters of polymers, and the interaction between gases and the polymer skeleton. At 298 K/1 bar, the polymers show high uptake for C₃H₈ (114.5 cm³ g^-1) and C₂H₆ (84.2 cm³ g^-1). Moreover, the adsorption selectivities of C₃H₈/CH₄, C₂H₆/CH₄, C₃H₈/C₂H₆, C₃H₈/CO₂, C₂H₆/CO₂, and CO₂/CH₄ also reach 296.3, 23.1, 9.0, 22.1, 4.1, and 5.0, respectively, exhibiting promising applications in adsorption/separation of C₁-C₃ hydrocarbons and stripping CO₂ gas from natural gas under the ambient condition.

Cost-effective preparation of microporous polymers from formamide derivatives and adsorption of CO2 under dry and humid conditions

Nitrogen-rich microporous polymers are prepared via a catalyst-free polymerization reaction using formamide derivatives as monomers, which exhibit outstandingly high CO₂/N₂ selectivity up to 151 and 173 at 273 K under dry and humid conditions, respectively.