Today’s growing demand for energy, materials and chemicals has prompted renewed interest in CO2 chemistry. One of the most abundant renewable resources of carbon is carbon dioxide. Due to the abundant availability of pure CO2 gas streams, it is only logical to promote a more widespread use of carbon dioxide as chemical feedstock. Notably, the use of CO2 for manufacturing materials and chemicals is still in its infancy. This Thematic Series presents intriguing approaches regarding different methodologies to activate carbon dioxide. Altogether, the articles present a remarkable overview of opportunities in the field of CO2 chemistry from many of its top practitioners. Exploiting carbon dioxide to create economic value will be the driving force for the more widespread use of this fascinating molecule.
Graphical Abstract
Scheme 1: Synthesis of poly(propylene carbonate) (PPC) using catalyst 1.
Scheme 2: PO/PA alternating copolymerization.
Figure 1: 1H NMR spectrum of crude products in the PO/PA alternating polymerization (A, entry 1 in Table 1), PO/CO2/...
Figure 2: GPC curves of the PO/PA copolymers.
Scheme 3: CO2/PO/PA terpolymerization.
Figure 3: DSC curves of PO/PA alternating polymer (A, entry 1 in Table 1), PO/CO2/PA terpolymer (B, entry 7 in Table 2), an...
Scheme 4: PA incorporation process in PO/CO2/PA terpolymerization.
Graphical Abstract
Scheme 1: Catalytic synthesis of organic (poly)carbonates from epoxides and CO2.
Figure 1: Structures of some metal complexes used as catalyst for (cyclic) organic carbonate synthesis.
Scheme 2: Proposed mechanistic cycle for cyclic carbonate synthesis mediated by Zn(salphen) complexes in the ...
Figure 2: Typical 1H NMR spectrum of a sample of a crude mixture in CDCl3 (300 MHz) at rt.
Scheme 3: Proposed mechanism for the formation of cyclic carbonates mediated by an ammonium salt.
Figure 3: Double logarithmic plot and to determinate the order in NBu4I. Conditions: 1,2-epoxyhexane (10 mmol...
Figure 4: Double logarithmic plot to determine the order in binary catalyst Zn(salphen) 1/NBu4I in the presen...
Figure 5: Double logarithmic plot to determine the order in binary catalyst Zn(salphen) 1/NBu4I in the presen...
Figure 6: Double logarithmic plot to determine the order with respect to the binary system NBu4I/Zn complex 1...
Figure 7: Proposed association for complex 2 and schematic structure for bifunctional complex 9.
Figure 8: Double logarithmic plot to determine the order in Zn complex 2. Conditions: 1,2-epoxyhexane (10 mmo...
Scheme 4: On the left a dimetallic mechanism proposed for bifunctional catalyst 2 and on the right a monometa...
Figure 9: Double logarithmic plot to determine the order with respect to the bifunctional Zn complex 2 in the...
Graphical Abstract
Figure 1: A visual representation of fluorocarbon surfactants at the air–water interface, highlighting the fr...
Figure 2: Correlation between relative surface coverage (Φsurf) – see Figure 1, limiting aqueous surface tension (γcmc...
Figure 3: Structures illustrating the difference in fraction free volume (FFV) within a surfactant tail regio...
Figure 4: Structures of three CO2-philic candidates: (30) MIA, (31) 2MEP and (32) 2MMP and the respective pol...
Figure 5: Structures of poly(1-decene) (37, P-1-D) and. poly(vinyl ethyl ether) (38, PVEE).
Figure 6: Schematic showing how hydrated cation radius (rhyd) mediates surfactant headgroup repulsions by con...
Figure 7: Abbreviated names and structures of hydrotropes tested by Hatzopoulos et al. [40,105,107].
Figure 8: Structures of para-methylphenol and para-ethylphenol. Para-substituted phenols have been shown to t...
Figure 9: Structures of 1,1,3,3-tetramethylguanidinium acetate (46), 1,1,3,3-tetramethylguanidinium lactate (...
Graphical Abstract
Scheme 1: Reactions of CO2 with amino-group containing absorbents (a), base/proton donor binary system (b) or...
Figure 1: Typical optimized structures of complex cations derived from chelation between Li+ and neutral liga...
Figure 2: (a) Comparison of the thermal stability between the neutral ligands and the corresponding chelated ...
Figure 3: In situ FTIR spectra of neutral ligands and the corresponding chelated ionic liquids after reaction...
Figure 4: Influence of the ratio of LiNTf2/neutral ligands (PEG150MeTMG and PEG150MeBu2N) on the CO2 capacity...
Figure 5: The quantum chemistry calculations (enthalpy changes) of the reaction between CO2 and [PEG150MeTMGL...
Graphical Abstract
Scheme 1: Synthesis of salicylic acid and p-hydroxybenzoic acid via Kolbe–Schmidt reaction [16-20].
Scheme 2: Electroreduction of carbon dioxide to formic acid, methanol or methane.
Scheme 3: Electrochemical fixation of CO2 in olefins.
Scheme 4: Electrohydrodimerisation of acrylonitrile to adiponitrile [32].
Scheme 5: Parallel paired electrosynthesis of phthalide and tert-butylbenzaldehyde dimethylacetal [34].
Scheme 6: Overview of electrocarboxylation setups using (a) a sacrificial anode, (b) an inert anode, generati...
Scheme 7: General mechanism of the electrochemical dicarboxylation of conjugated dienes [49].
Scheme 8: Reported anodic reactions for the electrocarboxylation of 1,3-butadiene.
Scheme 9: General mechanism for electrocarboxylation of alkynes.
Scheme 10: Electrocarboxylation of ethyl cinnamate [70].
Scheme 11: General electrocarboxylation mechanism for carbonyl compounds (Y = O) and imines (Y = NH) [75-77].
Scheme 12: Electrocarboxylation mechanism of butyraldehyde proposed by Doherty [78].
Scheme 13: Electrocarboxylation of AMN to HN using a sacrificial aluminum anode [86].
Scheme 14: Electrocarboxylation of benzalaniline using a sacrificial aluminum anode [105].
Scheme 15: Electrocarboxylation of p-isobutylacetophenone with stable electrodes [94,95].
Scheme 16: Electrochemical carboxylation of MMP to MHA [110,111].
Scheme 17: General mechanism for electrocarboxylation of alkyl halides [122,124-126,128].
Scheme 18: Electrocarboxylation of benzylic chlorides as synthesis route for NSAIDs.
Scheme 19: Electrocarboxylation of 1,4-dibromo-2-butene [144].
Scheme 20: Convergent paired electrosynthesis of cyanoacetic acid, with X− = F4B−, ClO4−, HSO4−, Cl−, Br− [147].
Scheme 21: General scheme of carboxylation of weak acidic hydrocarbons with electrogenerated bases. RH: weakly...
Scheme 22: Electrocarboxylation of N-methyldiglycolimide to methoxymethane-1,1,1’-tricarboxylate precursors. R1...
Scheme 23: Electrochemical dimerization of CO2 with stable electrodes [153].
Graphical Abstract
Figure 1: CO2 reduction to methanol in water promoted by FateDH, FaldDH and ADH where three consecutive 2e− s...
Figure 2: Transformed diffuse reflectance spectra of photocatalysts used in the present study.
Figure 3: a) Photoregeneration of 1,4-NADH using water as an electron donor: after 6 hours of irradiation of ...
Figure 4: 1H NMR spectra recorded at t = 0, after 2 and 6 h of irradiation in water. The selected range, 2–3 ...
Figure 5: 1H NMR spectrum of a standard 1,4-NADH (red line), and of 1,4-NADH formed from NAD+ upon photocatal...
Figure 6: Photocurrent generated at the [CrF5(H2O)]2−@TiO2 electrode as a function of the wavelength of the i...
Figure 7: Expected role of the rhodium complex as an electron mediator.
Figure 8: UV–vis absorption spectra of an aqueous solution of [Cp*Rh(bpy)(H2O)]2+. Continuous black line: spe...
Figure 9: Spectral changes of the [Cp*Rh(bpy)(H2O)]2+ solution as a function of the applied potential (left)....
Figure 10: Photoreduction of NAD+ as a function of concentration of glycerol (black line) and [Cp*Rh(bpy)H2O]Cl...
Figure 11: The electron flow in the photocatalytic system of NAD+ reduction composed of the photosensitized TiO...
Figure 12: Beads produced from Ca-alginate and TEOS containing co-encapsulated FateDH, FaldDH and ADH.
Figure 13: Assembled photocatalytic/enzymatic system for reduction of CO2 to CH3OH.
Graphical Abstract
Scheme 1: Structural motif of two important types of catalysts and typical substrate specificity in the copol...
Scheme 2: Binuclear Zn(II) complexes [LZn2](CF3SO3)2 (1, KOP113) and [LZn2](p-TSO3)2 (2, KOP115) explored in ...
Scheme 3: Copolymerisation of CO2 and cyclohexene oxide (*: end groups of the polymer chain).
Figure 1: Time-resolved IR spectra of the copolymerisation of CO2 and CHO with catalyst 1 showing the formati...
Figure 2: Time–concentration profile of the copolymerisation of CO2 and CHO in the presence of catalytic amou...
Figure 3: Carbonate region of the time-resolved IR spectra recorded during the copolymerisation of CO2 and cy...
Figure 4: Time–concentration profile of the copolymerisation of CO2 and CHO in the presence of catalytic amou...
Scheme 4: Proposed inner-sphere mechanism for the copolymerisation of CO2 and CHO with binuclear zinc complex...
Graphical Abstract
Figure 1: Selected examples for biologically active 4-hydroxy-2H-chromen-2-one and 4-hydroxy-2(1H)-quinolinon...
Scheme 1: Possible mechanism for the carboxylative cyclization of o-acetamidoacetophenone.
Scheme 2: Cross carboxylative cyclization reaction.
Graphical Abstract
Scheme 1: Reaction of carbon dioxide with epoxide to yield alternating polycarbonates, polyethercarbonates or...
Scheme 2: Epoxide and CO2 copolymerisation by homogeneous Cr(III)– and Al(III)–salen complexes.
Figure 1: The tri-coordinated di-iminate zinc–alkoxide complex [(BDI)ZnOCH3].
Scheme 3: Heterogeneous zinc dicarboxylates for the copolymerisation of CO2 and epoxides. (* = End group of p...
Scheme 4: Backbiting mechanism for the formation of cyclic carbonates.
Scheme 5: Two-step pathway for the cycloaddition of propylene oxide and CO2 in the ionic liquid 1-butyl-3-met...
Scheme 6: Formation of copper(I) cyanoacetate for the activation of CO2.
Scheme 7: Activation of CO2 by nucleophilic attack of bromide in the Re(I)-catalysed cycloaddition.
Scheme 8: Direct catalytic carboxylation of aliphatic compounds and arenes by rhodium(I)– and ruthenium(II)–p...
Scheme 9: Insertion of carbon dioxide into a metal–oxygen bond via a cyclic four-membered transition state. R...
Scheme 10: Facile CO2 uptake by zinc(II)–tetraazacycloalkanes.
Figure 2: The [(2-hydroxyethoxy)CoIII(salen)(L)] complex chosen as catalyst model for the calculations; 1: R1...
Figure 3: The two most relevant configurations of [(2-hydroxyethoxy)CoIII(salen)(L)] complexes. The left-hand...
Figure 4: Carbon dioxide insertion into the cobalt(III)–alkoxide bond of [(2-hydroxyethoxy)CoIII(salen)(L)] c...
Figure 5: Energy relationship between the activation barrier and the reaction energy of the CO2 incorporation...