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Carbon dioxide capture and utilization is a strategic technology for moving away from fossil‐C. The conversion of CO2 into fuels demands energy and hydrogen that cannot be sourced from fossil‐C. Co‐processing of CO2 and water under solar irradiation will have a key role in the long‐term for carbon‐recycling and energy products production. This article discusses the synthesis, characterization and application of the two‐phase composite photocatalyst, In2O3@g‐C3N4, formed by thermal condensation of melamine in the presence of indium(III)nitrate. The composite exhibits a n,n‐heterojunction between two n‐type semiconductors, g‐C3N4 and In2O3, leading to a more efficient charge separation. The composite has a flat band potential enabling it to effectively catalyze the reduction of CO2 in the gas phase to produce CO, CH4 and CH3OH. While the composite's overall photocatalytic efficiency is comparable to that of neat g‐C3N4, its ability to promote multielectron‐transfer and Proton Coupled to Electron Transfer (PCET) suggests that there is a potential for further optimization of its properties. The use of labelled 13CO2 has allowed us to clearly exclude that the reduced species are derived from the photocatalyst decomposition or the degradation of contaminants. [ABSTRACT FROM AUTHOR]

The photochemical and photoelectrochemical reduction of CO2 is a promising approach for converting carbon dioxide into valuable chemicals (materials) and fuels. A key issue is ensuring the accuracy of experimental results in CO2 reduction reactions (CO2RRs) because of potential sources of false positives. This paper reports the results of investigations on various factors that may contribute to erroneous attribution of reduced-carbon species, including degradation of carbon species contained in photocatalysts, residual contaminants from synthetic procedures, laboratory glassware, environmental exposure, and the operator. The importance of rigorous experimental protocols, including the use of labeled 13CO2 and blank tests, to identify true CO2 reduction products (CO2RPs) accurately is highlighted. Our experimental data (eventually complemented with or compared to literature data) underline the possible sources of errors and, whenever possible, quantify the false positives with respect to the effective conversion of CO2 in clean conditions. This paper clarifies that the incidence of false positives is higher in the preliminary phase of photo-material development when CO2RPs are in the range of a few 10s of μg gcat−1 h−1, reducing its importance when significant conversions of CO2 are performed reaching 10s of mol gcat−1 h−1. This paper suggests procedures for improving the reliability and reproducibility of CO2RR experiments, thus validating such technologies. [ABSTRACT FROM AUTHOR]

The enzymatic effectiveness in the reaction cascade that reduces CO2 to methanol in water at room‐temperature faces various constraints. One of the major challenges is the short life of costly enzymes: immobilization is used to make them more stable and recyclable. The comparative analysis of the several immobilization techniques reported in the literature is challenging due to the diverse reaction conditions (single enzyme test or pool of enzymes test) and experimental setups, as well as the high variability in the amount of enzymes and cofactor. In the present study, a comparison is presented among three different methods (co‐encapsulation into Ca–alginate beads, co‐absorption onto zirconium(IV) phosphate (ZrP) and covalent binding to dialdehydecellulose [DAC]) of co‐immobilization of the three dehydrogenases Fatedehydrogenase (DH), FaldDH, and alcohol dehydrogenase, used in equal amount and under the same experimental conditions, so to check at what extension the support and the immobilization method can influence the activity of the enzymatic pool. DAC is used for the first time to support the three DHs and results to be the best method of immobilization with respect to those used here, that also allows longer life on enzymes and repeated recycling of the supported enzymes, increasing the overall methanol production with respect to the free enzymes. [ABSTRACT FROM AUTHOR]

The mitigation of carbon dioxide is one of the scientific and technological challenges of the 2000s. Among the technologies that are under assessment, the recovery of carbon dioxide from power plants or industrial flue gases plays a strategic role. Recovered carbon dioxide can be either disposed in natural fields or used. The availability of large amounts of carbon dioxide may open new routes to its utilisation in biological, chemical and innovative technological processes. In this paper, the potential of carbon dioxide utilisation in the short-, medium-term is reviewed.

The need to decrease the concentration of CO2 in the atmosphere has led to the search for strategies to reuse such molecule as a building block for chemicals and materials or a source of carbon for fuels. The enzymatic cascade of reactions that produce the reduction of CO2 to methanol seems to be a very attractive way of reusing CO2; however, it is still far away from a potential industrial application. In this review, a summary was made of all the advances that have been made in research on such a process, particularly on two salient points: enzyme immobilization and cofactor regeneration. A brief overview of the process is initially given, with a focus on the enzymes and the cofactor, followed by a discussion of all the advances that have been made in research, on the two salient points reported above. In particular, the enzymatic regeneration of NADH is compared to the chemical, electrochemical, and photochemical conversion of NAD+ into NADH. The enzymatic regeneration, while being the most used, has several drawbacks in the cost and life of enzymes that suggest attempting alternative solutions. The reduction in the amount of NADH used (by converting CO2 electrochemically into formate) or even the substitution of NADH with less expensive mimetic molecules is discussed in the text. Such an approach is part of the attempt made to take stock of the situation and identify the points on which work still needs to be conducted to reach an exploitation level of the entire process. [ABSTRACT FROM AUTHOR]

This paper discusses the epochal change in the reputation of carbon dioxide, which is now considered as a raw material alternative to fossil C for the synthesis of chemicals, materials and fuels, as opposed to a waste material that must be confined underground. In particular, its use as renewable C is compared to biomass. In this paper, a specific point is discussed: is ethanol (or any fuel) produced via the catalytic conversion of atmospheric CO2 different from the relevant biomass-sourced product(s)? The answer to this question is very important because it ultimately determines whether or not fuels derived from atmospheric CO2 (either e-fuels or solar fuels) have the right to be subsidized in the same way that biofuels are. Conclusions are drawn demonstrating that ethanol derived from atmospheric CO2 deserves the same benefits as bio-ethanol, with the additional advantage that its synthesis can be less pollutant than its production via the fermentation of sugars. The same concept can be applied to any fuel derived from atmospheric CO2. [ABSTRACT FROM AUTHOR]

This review summarizes the deliberations of a workshop colloquium on the 'opportunities for catalysis research in carbon management'. Research progress within the context of greenhouse gas/carbon issues in the areas of hydrogen generation and utilization, carbon dioxide activation, catalysis research to further our search for new and more efficient catalytic processes.

The production of rhodium peroxocarbonate from RhCl(eta(super 2)-O2)(P)3, where P = PEt2Ph or PEtPh2, and CO2 occurs through a split in the O-O bond and insertion of CO2. The Rh-linked O atom of the peroxo group of RhCl(CO4)(P3) is responsible for the transfer of oxygen to the ancillary phosphine ligand to selectively form R3P=O. Data obtained from Raman, FTIR and NMR spectroscopic studies are discussed.

The vibrational modes and solution spectra for solid Ni(CO2)(PCy3)2 were established by FTIR and Raman spectroscopy. The two absorptions from CO stretching modes did not arise from crystal effect and they indicated that the coordination mode is identical in solution and solid state. The existence of the nu(CO) diad was due to Fermi resonance effect. The side-on conformer of the compound was observed to be more stable than the end-on one.

Solid state and solution NMR spectroscopy are utilized in determining how the bonding of carbon dioxide to transition metal systems is altered upon dissolution in a solvent. To this end, Ni(PCy3)2(CO2) is investigated. Results show that, in Ni(PCy3)(CO2) in solution at 173 degrees K, CO2 is bonded to nickel in an eta2-CO mode, while at room temperature, the CO2 molecule is fluxional. This may involve the increasing disengagement of the carbon atom from Ni to give an eta1-O intermediate.