An investigation of carbon dioxide capture by chitin acetate/DMSO binary system

POPs to COFs by post-modification: CO2 chemisorption and dissolution

Porous organic polymers (POPs) and covalent organic frameworks (COFs) are hierarchical nano materials with variable applications. To our knowledge, this is the first report of a post-modified, non-renewable, DMSO-soluble M-POP/1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) upon atmospheric H2O/CO2 trapping after 48 h, forming a DBUH+·HCO3- adduct, as verified by solution carbon-13 nuclear magnetic resonance (13C NMR) spectroscopy. The success of the post-modification resulting from aldehyde enriched POPs was proven spectroscopically. The accessible functional group was reacted with excess monoethanolamine (MEA) resulting in the formation of M-POP. Away from CO2 physisorption, only few examples have been reported on the chemisorption process. One such example is the ethylene diamine-functionalized E-COF, capable of capturing CO2via carbamation. This was evidenced by several qualitative measurements including colorimetry and conductivity, which showed an unprecedented water solubility for a 2D COF material. The crystallinity of COFs as a result of post-modification was proven by powder X-ray diffraction (PXRD).

CS2/CO2 Utilization Using Mukaiyama Reagent as a (Thio)carbonylating Promoter: A Proof-of-Concept Study

We report on the reaction of ethylene-terminated heteroatoms (C₂X; X = N, O, and S) with CS₂/CO₂ using Mukaiyama reagent (2-chloro-1-methylpyridinium iodide, CMPI) as a promoter for the preparation of imidazolidin-2-one, oxazolidin-2-one, 1,3-dioxolan-2-one, 1,3-dithiolan-2-one, and their thione counterparts at ambient temperature and pressure. Spectroscopic measurements, viz., ¹H/¹³C nuclear magnetic resonance (NMR) and ex situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy methods verified the reaction of CS₂/CO₂ with the ethylene-based substrates and subsequently the formation of cyclic products. The experimental data indicated the formation of the enol-form of imidazolidin-2-one and oxazolidin-2-one, while the keto-form was obtained for their thione correspondents. Furthermore, density functional theory calculations revealed the stability of the keto- over the enol-form for all reactions and pointed out the solvent effect in stabilizing the latter.

In situ activation of green sorbents for CO2 capture upon end group backbiting

Thermolysis of a urethane end group was observed as a first time phenomenon during activation. This unzipping mechanism revealed a new amine tethering point producing a diamine-terminated oligourea ([10]-OU), acting as a green sorbent for CO₂ capturing. The oligomer backbites its end group to form propylene carbonate (PC), as proved by in situ TGA-MS, which can reflect the polymer performance by maximizing its capturing capacity. Cross polarization magic angle spinning (CP-MAS) NMR spectroscopy verified the formation of the proven ionic carbamate (1:2 mechanism) with a chemical shift at 161.7 ppm due to activation desorption at higher temperatures, viz., 100 °C (in vacuo) accompanied with bicarbonate ions (1:1 mechanism) with a peak centered at 164.9 ppm. Fortunately, the amines formed from in situ thermolysis explain the abnormal behavior (carbamates versus bicarbonates) of the prepared sample. Finally, ex situ ATR-FTIR proved the decomposition of urethanes, which can be confirmed by the disappearance of the pre-assigned peak centered at 1691 cm^-1. DFT calculations supported the thermolysis of the urethane end group at elevated temperatures, and provided structural insights into the formed products.

Chemisorption of CO2 by diamine-tetraamido macrocyclic motifs: a theoretical study

Although alkanolamines have been systematically utilized for CO2 capture, intensive research efforts are still required to ultimately design more efficient CO2 sorbents with appropriate sorption characteristics. In this article, we have explored a series of diamine-tetraamido macrocyclic molecules with different organic linkers, namely, pyridine, phenylene, pyrrole, furan, and thiophene, for the titled purpose using quantum chemical calculations. The optimized structures of the sequestration reaction revealed the formation of a carbamate anion within the macrocyclic cavity that was stabilized through several intramolecular interactions compared to parent amines. The reaction thermodynamics indicated that the macrocyclic compounds with pyridine, pyrrole and furan can effectively capture CO2. The results highlight the potential application of macrocyclic structures as efficient CO2 capturing agents.

Mechanistic insights on CO2 utilization using sustainable catalysis

Caffeinium halides were used to catalyse the cycloaddition of CO2 to form cyclic carbonates. The reaction intermediates were isolated and characterized experimentally. The reaction mechanism has been confirmed by DFT calculations.

Activation of β-diketones for CO2 capture and utilization

β-Diketones are used for CO2 sequestration and utilization which was made possible due to their dual Brønsted acid/Lewis base character upon activation using a superbase,1,8-diazabicyclo[5.4.0]undec-7-ene or zinc bromide, respectively.

Cross-linked, porous imidazolium-based poly(ionic liquid)s for CO2 capture and utilisation

A series of micro/meso porous imidazolium poly(ionic liquid)s for CO2 capture and utilization is reported. They show moderate sorption capacity under RTP conditions, and good catalytic activity towards the cycloaddition of CO2 and epoxides to synthesize cyclic carbonates.

Marine collagen-chitosan-fucoidan cryogels as cell-laden biocomposites envisaging tissue engineering

The combination of marine origin biopolymers for tissue engineering (TE) applications is of high interest, due to their similarities with the proteins and polysaccharides present in the extracellular matrix of different human tissues. This manuscript reports on innovative collagen-chitosan-fucoidan cryogels formed by the simultaneous blending of these three marine polymers in a chemical-free crosslinking approach. The physicochemical characterization of marine biopolymers comprised FTIR, amino acid analysis, circular dichroism and SDS-PAGE, and suggested that the jellyfish collagen used in the cryogels was not denatured (preserved the triple helical structure) and had similarities with type II collagen. The chitosan presented a high deacetylation degree (90.1%) that can strongly influence the polymer physicochemical properties and biomaterial formation. By its turn, rheology, and SEM studies confirmed that these novel cryogels present interesting properties for TE purposes, such as effective blending of biopolymers without visible material segregation, mechanical stability (strong viscoelastic character), as well as adequate porosity to support cell proliferation and exchange of nutrients and waste products. Additionally, in vitro cellular assessments of all cryogel formulations revealed a non-cytotoxic behavior. The MTS test, live/dead assay and cell morphology assessment (phalloidin DAPI) showed that cryogels can provide a proper microenvironment for cell culturing, supporting cell viability and promoting cell proliferation. Overall, the obtained results suggest that the novel collagen-chitosan-fucoidan cryogels herein presented are promising scaffolds envisaging tissue engineering purposes, as both acellular biomaterials or cell-laden cryogels.

CO2 coupling with epoxides catalysed by using one-pot synthesised, in situ activated zinc ascorbate under ambient conditions

An in situ generated zinc ascorbate pre-catalyst for cyclic carbonate (CC) synthesis via CO₂ coupling with epoxides under ambient conditions was reported. Spectroscopic measurements indicated that CO₂ was inserted into the zinc ascorbate complex through the formation of an activated zinc carbonate catalyst upon abstracting the enediol protons with sodium hydride. The aliphatic diols were not activated under the applied conditions and did not interfere with either the process of cycloaddition or CO₂ activation. The catalyst was active against different terminal epoxides, with a conversion of 75 and 85%, when propylene oxide and styrene oxide were used at 20 and 50 °C, respectively under 1 atm CO₂ for 17 h, which was considered a good advancement for heterogeneous based catalysis. Moreover, green chemistry principles were applied to ultimately end up with more ecofriendly approaches for the synthesis of CC following a simple balloon technique. Herein, we used zinc as a sustainable metal, together with ascorbic acid as a bio-renewable material in addition to CO₂ as a renewable feed-stock. Furthermore, waste prevention was achieved using the reaction side product, viz., NaBr as a co-catalyst.

The eternal battle to combat global warming: (thio)urea as a CO2 wet scrubbing agent

(Thio)Urea scaffolds are best known for their importance as intermediates in organic synthesis. In this work, a mechanistic study of the reaction between urea (U), (2-hydroxyethyl)urea (U-EtOH) and thiourea (tU)/NaH in DMSO with CO2 was carried out. While both U/tU reacted with CO2via a 1 : 2 mechanism through the formation of the keto (thio)carbamide-carboxylate adducts (k-U/tU-CO2- Na+), U-EtOH gave mixed CO2-adducts composed of organic carbonate and carbamide-carboxylate moieties (Na+-CO2-U-Et-OCO2- Na+). Moreover, we recorded for the first time, a new type of bond, namely sodium carbamimidothiocarbonate (e-tU-SCO2- Na+), upon bubbling CO2 in the DMSO solution of tU due to the persistence of the enol form (e-tU) and the better nucleophilicity of sulfur over nitrogen focal points. The reaction mechanisms were proven by 1D and 2D nuclear magnetic resonance (NMR) and ex situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopies. The stability of these bonds was studied following the changes in 1H-NMR as a function of temperature, which indicated the reversibility of these reactions. Furthermore, the proposed mechanisms were explored theoretically via density functional theory (DFT) calculations by analyzing the energetics of the anticipated products.

CO2 activation through C–N, C–O and C–C bond formation

CO₂ fixation reactions have been explored using different organic substrates upon activation with a superbase.

Biomaterials for CO2 Harvesting: From Regulatory Functions to Wet Scrubbing Applications

A new series of 2-aminoethyl-benzene-based biomaterials, namely, dopamine (DOP), tyramine (TYR), phenylethylamine (PEA), and epinephrine (EPN), dissolved in dimethylsulfoxide (DMSO) have been investigated for CO2 capture upon activatiing their hydhydrochloride salts  with a NaOH pellet. Spectroscopic measurements, including ex situ ATR-FTIR, 1D and 2D NMR experiments have been applied to verify the formation of the sodium carbamate adducts (RR'N-CO2 - Na+). The emergence of new peaks in the IR spectra ranging between 1702 and 1735 cm-1 together with the chemical shift within 157-158 ppm in the 13C NMR, as well as with cross-peaks obtained by 1H-15N HSQC measurements at ca. 84 and 6.6 ppm verified the formation of RR'N-CO2 - Na+ products upon the chemical fixation of CO2. The CO2 sorption capacity of the examined biomaterials was evaluated volumetrically, with a maximum value of 8.18 mmol CO2·g-1 sorbent (36.0 (w/w)%, including both chemisorption and physisorption), for 5 (w/v)% solutions measured at 5 bar CO2 and 25 °C, for TYR and PEA. DFT calculations indicated that the intramolecular hydrogen bonding within the structural motif of EPN-N-CO2 - Na+ adduct provides an exceptional stability compared to monoethanolamine and other structurally related model compounds.

A catecholamine neurotransmitter: epinephrine as a CO2 wet scrubbing agent

Bio-renewables are emerging as potential materials for CO2 sorption. Epinephrine is employed as a green scrubbing agent for CO2 capturing through the formation of a metal carbamate as proved by 1H, 13C and 1H-15N NMR and ex situ ATR-FTIR spectroscopy, as well as supported by quantum-chemical calculations.

Inedible saccharides: a platform for CO2 capturing

The economic viability of eco-friendly and renewable materials promotes the development of an alternative technology for climate change mitigation. Investigations reported over the past few years have allowed understanding the mechanism of action for a wide spectrum of saccharides toward carbon dioxide (CO2), in terms of reactivity, reversibility, stability and uptake. Exploiting bio-renewables, viz., inedible saccharides, to reduce the anthropogenic carbon footprint upon providing a sustainable and promising technology that is of interest to different groups of scientists, to overcome demerits associated with the current state-of-the-art aqueous amine scrubbing agents, following a "green chemistry guideline", by employing materials with properties relevant to the environment toward sustainable development. The interdisciplinary nature of research in this area provides a large body of literature that would meet the interest of the broad readership of different multidisciplinary fields. Although many reports emphasize the use of biomass in various industrial products ranging from pharmaceutics, medical preparations, soaps, textiles, cosmetics, household cleaners, and so on, to our knowledge there is no focused article that addresses the application of saccharides for CO2 sequestration. In this review, we highlight the recent advances on the use of oligo-, poly- and cyclic saccharides to achieve a reversible binding of CO2. The future research directions are discussed to provide insight toward achieving sustainable development through implementing bio-renewables.

A green sorbent for CO2 capture: α-cyclodextrin-based carbonate in DMSO solution

α-Cyclodextrin dissolved in DMSO is a potential sorbent for CO₂ capture through the exclusive formation of ionic organic carbonate.

New insights into the chemistry of ionic alkylorganic carbonates: a computational study

A library of hydrogenated, perfluorinated aliphatic and aromatic alcohols are selected together with a combination of superbases and metal hydrides to understand the thermodynamics of the binary mixtures once serving as sorbents for the capture of CO₂via ionic organic alkylcarbonate formation.

Bis-tris propane in DMSO as a wet scrubbing agent: carbamic acid as a sequestered CO2 species

We report the chemisorption of CO₂ by bis-tris propane dissolved in DMSO via carbamic acid formation.