A theoretical investigation of the CO2-philicity of amides and carbamides

Fabrication of Hollow Nanocones Membrane with an Extraordinary Surface Area as CO2 Sucker

Recently, more and more attention has been paid to the development of eco-friendly solid sorbents that are cost-effective, noncorrosive, have a high gas capacity, and have low renewable energy for CO₂ capture. Here, we claimed the fabrication of a three-dimensional (3D) film of hollow nanocones with a large surface area (949.5 m²/g), a large contact angle of 136.3°, and high surface energy. The synthetic technique is based on an electrochemical polymerization process followed by a novel and simple strategy for pulling off the formed layers as a membrane. Although the polymer-coated substrates were reported previously, the membrane formation has not been reported elsewhere. The detachable capability of the manufactured layer as a membrane braked the previous boundaries and allows the membrane’s uses in a wide range of applications. This 3D hollow nanocones membrane offer advantages over conventional ones in that they combine a π-electron-rich (aromatic ring), hydrophobicity, a large surface area, multiple amino groups, and a large pore volume. These substantial features are vital for CO₂ capturing and storage. Furthermore, the hydrophobicity characteristic and application of the formed polymer as a CO₂ sucker were investigated. These results demonstrated the potential of the synthesized 3D hollow polymer to be used for CO₂ capturing with a gas capacity of about 68 mg/g and regeneration ability without the need for heat up.

Electronic Interactions in Iminophosphorane Superbase Complexes with Carbon Dioxide

Iminophosphoranes or phosphazenes are an important class of compounds with increasing use in synthetic organic chemistry as neutral organic superbases exhibiting low nucleophilicity. Their electronic structure and therefore their properties strongly depend on substitution, but there have been very few theoretical studies devoted to this topic, and more specifically to the formation of electron donor-acceptor complexes of iminophosphoranes with electrophiles. In this work, we have investigated the interaction with carbon dioxide at different ab initio levels. Carbon dioxide usually behaves as a Lewis acid and the reaction with iminiphosphoranes has been described as a nonconventional aza-Wittig process leading to isocyanates. The reaction can be conducted in supercritical CO₂ conditions (carbon dioxide acts as both solvent and reactant), which is a promising strategy in the context of green chemistry. Our calculations have been carried out at the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ level for model systems and at the M06-2X/6-611+G(d,p) level for a larger species used in experiments. The electronic interactions and the interaction energies are analyzed and discussed in detail using the natural bond orbital method. Proton affinities and gas-phase basicities are provided as well.

Synthesis of Size-Tunable CO2-Philic Imprinted Polymeric Particles (MIPs) for Low-Pressure CO2 Capture Using Oil-in-Oil Suspension Polymerization

Highly selective molecularly imprinted poly[acrylamide-co-(ethylene glycol dimethacrylate)] polymer particles (MIPs) for CO₂ capture were synthesized by suspension polymerization via oil-in-oil emulsion. Creation of CO₂-philic, amide-decorated cavities in the polymer matrix led to a high affinity to CO₂. At 0.15 bar CO₂ partial pressure, the CO₂/N₂ selectivity was 49 (corresponding to 91% purity of the gas stream after regeneration), and reached 97 at ultralow CO₂ partial pressures. The imprinted polymers showed considerably higher CO₂ uptakes compared to their nonimprinted counterparts, and the maximum equilibrium CO₂ capture capacity of 1.1 mmol g^-1 was achieved at 273 K. The heat of adsorption was below 32 kJ mol^-1 and the temperature of onset of intense thermal degradation was 351-376 °C. An increase in monomer-to-cross-linker molar ratio in the dispersed phase up to 1:2.5 led to a higher affinity toward CO₂ due to higher density of selective amide groups in the polymer network. MIPs are a promising option for industrial packed and fluidized bed CO₂ capture systems due to large particles with a diameter up to 1200 μm and irregular oblong shapes formed due to arrested coalescence during polymerization, occurring as a result of internal elasticity of the partially polymerized semisolid drops.

Modeling Solvation in Supercritical CO2

In recent decades, a microscopic understanding of solute-solvent intermolecular interactions has been key to advances in technologies based on supercritical carbon dioxide. In many cases, computational work has provided the impetus for new discoveries, shedding new light on important concepts such as the local structure around the solute in the supercritical medium, the influence of the peculiar properties of the latter on the molecular behavior of dissolved substances and, importantly, CO₂ -philicity. In this Review, the theoretical work that has been relevant to these developments is surveyed and, by presenting some crucial open questions, the possible routes to achieving further progress based on the interplay between theory and experiments is discussed.

CO2 Capture and Separations Using MOFs: Computational and Experimental Studies

This Review focuses on research oriented toward elucidation of the various aspects that determine adsorption of CO₂ in metal-organic frameworks and its separation from gas mixtures found in industrial processes. It includes theoretical, experimental, and combined approaches able to characterize the materials, investigate the adsorption/desorption/reaction properties of the adsorbates inside such environments, screen and design new materials, and analyze additional factors such as material regenerability, stability, effects of impurities, and cost among several factors that influence the effectiveness of the separations. CO₂ adsorption, separations, and membranes are reviewed followed by an analysis of the effects of stability, impurities, and process operation conditions on practical applications.

Structure-Property Relationships in CO2-philic (Co)polymers: Phase Behavior, Self-Assembly, and Stabilization of Water/CO2 Emulsions

This Review provides comprehensive guidelines for the design of CO2-philic copolymers through an exhaustive and precise coverage of factors governing the solubility of different classes of polymers. Starting from computational calculations describing the interactions of CO2 with various functionalities, we describe the phase behavior in sc-CO2 of the main families of polymers reported in literature. The self-assembly of amphiphilic copolymers of controlled architecture in supercritical carbon dioxide and their use as stabilizers for water/carbon dioxide emulsions then are covered. The relationships between the structure of such materials and their behavior in solutions and at interfaces are systematically underlined throughout these sections.

Toward a Delaminated Organotalc: The Use of Polyamidoamine Dendrons

A sequence of generations of the polyamideamine dendron, PAMAM-talc-Gn (n = 1-7), was constructed on the surfaces of ethylenediaminepropyl-functionalized magnesium phyllosilicate lamellas by using a modified microwave-assisted synthesis. The successful functionalization of the inorganic layers by the organic dendrimer was confirmed by FTIR and (13)C NMR spectroscopies, elemental analyses, and thermogravimetric analysis (TGA). The solid materials presented an increase in their interlamellar space and disorganization of lamella packing with the growth of the dendrons. Thermal-programmed desorption analysis showed that the lower dendron generation, PAMAM-talc-G1, adsorbed 1.30 mmol of CO2/g of sorbent at 30 °C. PAMAM-talc-G5 adsorbed the double of PAMAM-talc-G3, probably due to the higher amount of the primary amine group; however, PAMAM-talc-G5 adsorbed more CO2 than PAMAM-talc-G7 probably because in the delaminated seventh generation intradendron N-H interactions were more prevalent than in the fifth generation and blocked CO2 interaction sites.

Driving Forces Controlling Host-Guest Recognition in Supercritical Carbon Dioxide Solvent

The formation of supramolecular host-guest complexes is a very useful and widely employed tool in chemistry. However, supramolecular chemistry in non-conventional solvents such as supercritical carbon dioxide (scCO2 ), one of the most promising sustainable solvents, is still in its infancy. In this work, we explored a successful route to the development of green processes in supercritical CO2 by combining a theoretical approach with experiments. We were able to synthesize and characterize an inclusion complex between a polar aromatic molecule (benzoic acid) and peracetylated-β-cyclodextrin, which is soluble in the supercritical medium. This finding opens the way to wide, environmental friendly, applications of scCO2 in many areas of chemistry, including supramolecular synthesis, reactivity and catalysis, micro and nano-particle formation, molecular recognition, as well as enhanced extraction processes with increased selectivity.

Chalcogen bonds in complexes of SOXY (X, Y = F, Cl) with nitrogen bases

SOF2, SOFCl, and SOCl2 were each paired with a series of N bases. The potential energy surface of the binary complexes were characterized by MP2 calculations with double and triple-ξ basis sets, extrapolated to complete sets. The most stable configurations contained a S···N chalcogen bond with interaction energies as high as 6.8 kcal/mol. These structures are stabilized by a Nlp → σ*(S-Z) electron transfer (Z = O, F, Cl), complemented by Coulombic attraction of N to the σ-hole opposite the Z atom. N···S-F and N···S-Cl chalcogen bonds are stronger than N···S═O interactions. Formation of each chalcogen bond elongates all of the internal covalent bonds within SOXY, especially the S-Cl bond. Halogen-bonded (N···Cl-S) complexes were also observed, but these are more weakly bound, by less than 3 kcal/mol.

Ab initio analysis on the interaction of CO2 binding to peracetated D-glucopyranose

CO2-philes can be utilized as additives, surfactants, and a potential phase-change physical solvent or absorbent for CO2, so the design and synthesis of CO2-philes typically non-fluorous compounds is important to develop more application areas of CO2. Researchers have recently reported that peracetated D-glucopyranose has high solubility in CO2. In order to study the interaction properties between sugar acetates with CO2, 1,2-di-O-acetyl-α-D-glucopyranose and 1,2-di-O-acetyl-β-D-glucopyranose were decided as substrates after initial chemical stimulations with peracetated D-glucopyranose, and the complex model was one CO2 molecule combined with one sugar substrate (1:1). Ab initio calculations of these two systems were accomplished including geometry optimizations with HF/3-21G, B3LYP/6-31+G**, and single point energies calibration with MP2/aug-cc-pVDZ. The results indicated that hydrogen atoms can interact with CO2 by C-H··O hydrogen bond, but the dominant ones are the interactions of oxygen atoms in substrates with a CO2 molecule. It was also found that the binding energies increased when more oxygen atoms of substrate interacted with CO2, but were not affected by their chemical environment. The interaction of sugar substrate with CO2 is distance related, and should be an electrostatic interaction not only Lewis acid-Lewis base and hydrogen bond interactions. Therefore, it can be expected that one CO2-phile could interact with more CO2 molecules if more acetate-like groups or oxygen atoms were introduced into the molecular structure based on all these results, and this can be a guideline for design CO2-philes.

Strongly bound noncovalent (SO3)n:H2CO complexes (n = 1, 2)

SO₃and H₂CO dimers and trimers are held together by S⋯O chalcogen bonds, supplemented by weaker CH⋯O and/or O⋯C bonds.

Complexes containing CO2and SO2. Mixed dimers, trimers and tetramers

Two stable minima for the 1 : 1 heterodimer of CO₂ : SO₂, both bound by about 2 kcal mol⁻¹. Binding is dominated by charge transfer from O lone pairs of SO₂to CO π* antibonding orbitals.