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Carbon dioxide (CO

The direct conversion of naturally abundant carbonyl compounds provides a powerful platform for the efficient synthesis of valuable chemicals. In particular, the conversion of ketones to alkenes is a commonly encountered chemical transformation, often achieved via the multistep Shapiro reaction with tosylhydrazone and over stoichiometric organolithium or Grignard reagent. Herein, we report an earth abundant nickel-catalyzed alkenylation of naturally abundant methylene ketones to afford a wide range of alkene derivatives, mediated by hydrazine. The protocol features a broad substrate scope (including alkyl ketones, aryl ketones, and aldehydes), good functional group compatibility, mild reaction conditions, water tolerance, and only environmentally friendly N

The electrocatalytic reduction of CO2 coupled with the oxidation of 5-hydroxymethylfurfural in a single cell based on molecular catalysts was successfully conducted with high faradaic efficiency, which could successfully be driven by solar energy.

The phosphorus-doped hollow polygonal g-C3N4 rods were prepared and applied to photocatalytic CO2 reduction reaction with [Co(bpy)3]Cl2 as co-catalyst, delivering a CO evolution rate up to 447.5 μmol g−1 h−1 with a selectivity ca. 96%.

The palladium-catalyzed four-component carboxylative cyclization of propargylic amines, aryl iodides, CO2 and CO was developed, which has broad substrate scope and application prospects.

The O-β-oxoalkyl carbamates were synthesized via the visible light-initiated HAT pathway from CO2, amines and inactive substrates with the assistance of CBr4, leading to simultaneous construction of C–O and C–N bonds under ambient conditions.

Electrochemically induced sulfonylation of alkenes with disulfides as the starting reagents was developed. This transformation is a quite rare example of disulfides usage as S-partners in electrochemical C-S coupling. In...

The photocatalytic reduction of CO2 into fuels offers the prospect for creating a new CO2 economy. Harnessing visible light-driven CO2 -to-CO reduction mediated by the long-lived triplet excited state of rhenium(I) tricarbonyl complexes is a challenging approach. We here develop a series of new mononuclear rhenium(I) tricarbonyl complexes (Re-1-Re-4) based on the imidazole-pyridine skeleton for photo-driven CO2 reduction. These catalysts are featured by combining pyridyl-imidazole with the aromatic ring and different pendant organic groups onto the N1 position of 1,3-imidazole unit, which display phosphorescence under Ar-saturated solution even at ambient conditions. By contrast, {Re[9-(pyren-1-yl)-10-(pyridin-2-yl)-9H-pyreno[4,5-d]imidazole)](CO)3 Cl} (Re-4) by introducing pyrene ring at the N1 position of pyrene-fused imidazole unit exhibits superior catalytic performance with a higher turnover number for CO (TONCO =124) and >99.9 % selectivity, primarily ascribed to the strong visible light-harvesting ability, long-lived triplet lifetimes (164.2 μs) and large reductive quenching constant. Moreover, the rhenium(I) tricarbonyl complexes derived from π-extended pyrene chromophore exhibit a long lifetime corresponding to its ligand-localized triplet state (3 IL) evidenced from spectroscopic investigations and DFT calculations.

Invited for the cover of this issue is the group of Liang-Nian He at Nankai University. The image depicts that 2D ultrathin metal organic layers (MOLs) with bis-metallic catalytic sites make an efficient photocatalyst resulting in efficient and selective visible-light-driven CO

The electrocatalytic CO

A series of diatomite supported Cu/Ni bimetallic catalysts were prepared using the co-impregnation method to improve the efficiency and selectivity toward methyl 12-hydroxystearate in the hydrogenation of methyl ricinoleate. The catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (H2-TPR). All the characterization results verified the formation of highly dispersed Cu/Ni alloy on support. Moreover, by subtly regulating the Ni/Cu molar ratio as well as the reaction parameters, the hydrogenation of methyl ricinoleate to methyl 12-hydroxystearate proceeded efficiently and selectively, affording 97% yield of methyl 12-hydroxystearate and nearly equivalent conversion of methyl ricinoleate under 2 MPa H2 pressure and at 130 °C in 4 h with only 1 wt% of the catalyst Ni7Cu1/diatomite (based on methyl ricinoleate). Besides, the supported Cu–Ni bimetallic catalyst is stable during recycle and reuse. After five cycles of reuse, much catalytic activity is still preserved. Therefore, this low-cost and stable bimetallic catalyst would be promising for the hydrogenation of methyl ricinoleate to methyl 12-hydroxystearate, representing an example of green catalysis for efficiently conversion of biomass to value-added chemicals and materials.

Significant efforts have been devoted to the photochemical CO2 reduction reaction (CO2RR) as a significant pathway for the development of renewable energy systems. However, the competitive hydrogen evolution reaction (HER) greatly impedes the fundamental understanding and industrial application of the CO2RR. Herein, we report polyhedral oligomeric silsesquioxane (POSS)-based porous organometallic polymers (POMPs) that are able to catalyze the photochemical CO2RR to produce syngas. Their surface area, CO2 adsorption ability, visible-light harvesting capacity and photoinduced electron–hole separation efficiency can be regulated by tuning the Re-bipyridine content in POMPs. Consequently, the effects of these properties on CO2RR and HER activities have been investigated and the surface area and electron transfer efficiency of these materials have been elucidated as the key points. Importantly, we also reveal the applicability of the developed strategy in designing new catalysts for the CO2RR.

CO2 valorization into valuable chemicals has attracted much attention, among which carboxylative cyclization represents an appealing transformation strategy to synthesize heterocyclic compounds. Conventionally, the carboxylative cyclization comprises CO2 capture and subsequent nucleophilic attack of the resulting carboxylic anion to an unsaturated bond, by which the monofunctionalization of the unsaturated bond is realized and the heterocyclic compounds, such as 5-/6-membered cyclolactone, cyclocarbonate, and oxazolidinone, are accordingly generated. Nowadays, the CO2-participated multicomponent carboxylative cyclizations have evoked intense interest due to their ability to perform the bifunctionalization of the unsaturated bond in the ring-closing step, thus assembling complex molecules. Up to now, by activating the unsaturated bonds with functionalized reagents and designing cascade reactions of organometallic compounds, substituents including iodine, trifluoromethyl, perfluoroalkyl, alkyl, cyanoalkyl, allyl, aryl, phenoxy, allenyl, selenyl, amino, and phosphonyl groups have been incorporated into the cyclocarbonate or oxazolidinone compounds successfully through the multicomponent carboxylative cyclizations. Given the tremendous utility of this synthetic strategy in heterocyclic compound synthesis, this review summarizes the progress of multicomponent carboxylative cyclizations to spur the further development of this field.

An intriguing strategy for copper-catalyzed hydroxymethylation of alkynes with CO2 and hydrosilane was developed. Switched on/off a proton source, for example, t BuOH, direct hydroxymethylation and reductive hydroxymethylation could be triggered selectively, delivering a series of allylic alcohols and homobenzylic alcohols, respectively, with high levels of Z/E, regio- and enantioselectivity. Such a selective synthesis is attributed to the differences in response of vinylcopper intermediate to proton and CO2 . The protonation of vinylcopper species is demonstrated to be prior to hydroxymethylation, thus allowing a diversion from direct alkyne hydroxymethylation to reductive hydroxymethylation in the presence of suitable proton.

Compounds bearing organophosphorus motifs and 2-oxazolidinone have found numerous applications in pharmaceutical chemistry, homogeneous catalysis, and organic materials. Here, we describe an efficient and selective protocol for straightforward access to a series of 5-((diarylphosphoryl)methyl)oxazolidin-2-ones via the copper-catalyzed difunctionalization of the C≡C bond of propargylic amines with CO2 and phosphine oxide. Notably, copper catalysis is a sustainable and benign catalytic mode. This reaction proceeds under mild reaction conditions, which is operationally simple and scalable with a broad scope, exclusive selectivity, and good functional group compatibility. Mechanistic studies suggest a one-pot tandem cyclization/radical addition sequence, along with the phosphorylation/cyclization scheme.

A series of functionalized ionic liquids (ILs) were developed for the reductive functionalization of CO2 with amine and hydrosilane to afford formamides under mild conditions. It was found that 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-based IL i.e. [DBUC12]Br showed high efficiency for the N-formylation reaction of amines without using any organic solvents or additives. Furthermore, control experiments suggested the cations with active hydrogen may weaken the nucleophilicity of anions through ion pairing interactions, thereby affecting the activation of hydrosilane. The reaction mechanism was then investigated by Density Functional Theory (DFT) calculations. This protocol represents a highly efficient and environmentally friendly example for catalytic conversion of CO2 into value-added chemicals such as formamide derivatives by employing DBU functionalized ILs.

The reaction of propargylic amines and CO2 can provide high-value-added chemical products. However, most of catalysts in such reactions employ noble metals to obtain high yield, and it is important to seek eco-friendly noble-metal-free MOFs catalysts. Here, a giant and lantern-like [Zn116 ] nanocage in zinc-tetrazole 3D framework [Zn22 (Trz)8 (OH)12 (H2 O)9 ⋅8 H2 O]n Trz=(C4 N12 O)4- (1) was obtained and structurally characterized. It consists of six [Zn14 O21 ] clusters and eight [Zn4 O4 ] clusters. To our knowledge, this is the highest-nuclearity nanocages constructed by Zn-clusters as building blocks to date. Importantly, catalytic investigations reveal that 1 can efficiently catalyze the cycloaddition of propargylic amines with CO2 , exclusively affording various 2-oxazolidinones under mild conditions. It is the first eco-friendly noble-metal-free MOFs catalyst for the cyclization of propargylic amines with CO2 . DFT calculations uncover that ZnII ions can efficiently activate both C≡C bonds of propargylic amines and CO2 by coordination interaction. NMR and FTIR spectroscopy further prove that Zn-clusters play an important role in activating C≡C bonds of propargylic amines. Furthermore, the electronic properties of related reactants, intermediates and products can help to understand the basic reaction mechanism and crucial role of catalyst 1.

In this work, the protic ionic liquid [DBUH][Im] (1,8-diazabicyclo[5.4.0]-7-undeceniumimidazolide) was developed as an efficient catalyst for the transesterification of ethylene carbonate with methanol to produce dimethyl carbonate. At 70 °C, up to 97% conversion of ethylene carbonate and 91% yield of dimethyl carbonate were obtained with 1 mol% [DBUH][Im] (relative to ethylene carbonate) as catalyst in 2 h. Even at room temperature, the conversion of ethylene carbonate can reach 94% and the yield of dimethyl carbonate can approach 81% for 6 h. Catalytic mechanism investigation showed the high catalytic efficiency of this ionic liquid results from the synergistic activation effect, wherein the cation can activate ethylene carbonate and the anion can activate methanol through hydrogen bond formation. Although the reusability of the ionic liquid need to be further improved, high efficiency and commercial availability of [DBUH][Im] render it a promising catalyst for the preparation of dimethyl carbonate.

An efficient dual-ligand zeolitic imidazolate framework ZIF-8-90 was fabricated for the synthesis of five-membered cyclic carbonate from CO2 and epichlorohydrin (ECH) in the absence of co-catalysts and solvents. The effects of various reaction parameters were studied. The dual-ligand ZIF-8-90 showed very high selectivity (up to 99%). ZIF-8-90 exhibited better catalytic ability with lower cost than ZIF-90 and enhanced framework stability with significantly improved selectivity compared to ZIF-8. Moreover, the catalyst has been successfully reused for three cycles with negligible decrease in the catalytic activity. A plausible mechanism for the ZIF-8-90 catalyzed ECH−CO2 cycloaddition under solvent-free and co-catalyst-free has been proposed.

Developing effective sunlight-driven systems for CO2 reduction is one of the most promising subjects from the perspective of sustainably producing solar fuels. Herein, we develop a strategy to boost CO2 reduction performance by enhancing intermolecular electron transfer efficiency and visible light-absorption ability by introducing bifunctional pyrene groups on the ligand. This catalyst exhibits high-efficiency performance for natural light-powered CO2 reduction (TONCO up to 350 ± 36, ΦCO up to 46.6 ± 3%). This is the first report on using a single-molecule photocatalyst for CO2 reduction under natural conditions. Through the combination of experimental results and DFT calculations, the appending pyrene groups have been proven to promote the catalyst's ability to harness visible light as well as facilitate electron transfer (ET) through intermolecular π–π interactions. Due to the accelerated intermolecular ET, TONCO can be further boosted up to 1367 ± 32 in the presence of the ruthenium photosensitizer. Moreover, an enhancement in CO2 electroreduction performance can also be observed for the pyrenyl-functionalized rhenium catalyst further highlighting the versatile applications of this methodology.

With the increasing awareness of sustainable chemistry and green chemistry, photochemical CO2 fixation has drawn more and more attention in response to the need for renewable C1 resources and inexhaustible clean energy resources. It is appealing to provide carboxylic acids and derivatives using CO2 as a renewable feedstock, which is widely used in the manufacture of pharmaceuticals, pesticides, dyes and other fine chemicals. Classifying them by the types of reaction sites, this review presents an overview of the recent advances and achievements in the photocarboxylation of C(sp3)–X (X = H, N) bonds, C(sp2)–X (X = H, N, (pseudo)halide) bonds and C(sp)–H bonds with CO2, with an emphasis on the mechanistic aspects of the reactions and a perspective on their future prospects, hopefully stimulating the further research and development of this appealing field.