Cobalt-based catalysis for carboxylative cyclization of propargylic amines with CO2 at atmospheric pressure

Design and application of g-C3N4-based materials for fuels photosynthesis from CO2 or H2O based on reaction pathway insights

Photocatalytic CO2 reduction reaction (CRR) and hydrogen evolution reaction (HER) based on graphitic carbon nitride (g-C3N4) that is regarded as the metal-free "holy grail" photocatalyst, provide promising strategies for producing next-generation fuels, contributing to achieving carbon neutrality, alleviating energy and environment crisis. However, the activity of CRR and HER over g-C3N4 leaves much to be desired. Therefore, numerous studies have sprung up to enhance photoactivity. A comprehensive understanding of the CRR and HER reaction pathways is crucial for designing g-C3N4-based materials, further promoting efficient fuel production. Different from previous reviews that focus on g-C3N4 modification from the viewpoint of material science. In this review, we divided the multistep processes of CRR and HER into five reaction pathways and summarized the latest advances for improving each pathway of fuels synthesis through CRR or HER. Meanwhile, the existing bottleneck issues of each step were also discussed. Finally, comprehensive conclusions, including the remaining challenges, outlooks, etc., for CRR and HER over g-C3N4 were put forward. We are sure that this review will conduce to the understanding of the structure-activity relationship between CRR, HER processes, and g-C3N4 structure, which can provide the reference for developing high-powered photocatalysts, not confined to g-C3N4.

MOF-Incorporated Binuclear N-Heterocyclic Carbene-Cobalt Catalyst for Efficient Conversion of CO2 to Formamides

Environmental problem caused by carbon emission is of widespread concern. Involving CO₂ as C₁ resource into chemical synthesis is one of the most attractive ways for carbon recycling. Herein, the first example of host-guest composites featuring metal-organic framework (MOF)-encapsulated binuclear N-heterocyclic carbene (NHC) complex, Co₂ @MIL101, was developed with the molecularly dispersed [Co(IPr)Br]₂ (μ-Br)₂ (Co₂ ) loading in the cage of MIL-101(Cr) via a "ligand-in-dimer-trap" strategy, which was comprehensively investigated through various techniques including synchrotron X-ray absorption, electron microscopy, X-ray diffraction, solid-state nuclear magnetic resonance spectroscopy, and others. The noble-metal-free double-sites catalyst Co₂ @MIL101 exhibited promising stability, activity, efficiency, reusability, and substrate adaptability for converting CO₂ into various formamides with amines and hydrosilanes and achieved the best performance for one of the most useful formamides, N-methyl-N-phenylformamide (MFA), among the recyclable catalysts at ambient conditions, providing a reliable approach to successfully unify the advantages of both homo- and heterogeneous catalysts. Density functional theory calculations were applied to illustrate the superior activity of the binuclear NHC complex center as double-sites catalyst toward the activation of CO₂ .

Nitrogen-Rich Porous Organic Polymers with Supported Ag Nanoparticles for Efficient CO2 Conversion

As CO₂ emissions increase and the global climate deteriorates, converting CO₂ into valuable chemicals has become a topic of wide concern. The development of multifunctional catalysts for efficient CO₂ conversion remains a major challenge. Herein, two porous organic polymers (NPOPs) functionalized with covalent triazine and triazole N-heterocycles are synthesized through the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The NPOPs have an abundant microporous content and high specific surface area, which confer them excellent CO₂ affinities with a CO₂ adsorption capacity of 84.0 mg g^-1 and 63.7 mg g^-1, respectively, at 273 K and 0.1 MPa. After wet impregnation and in situ reductions, Ag nanoparticles were supported in the NPOPs to obtain Ag@NPOPs with high dispersion and small particle size. The Ag@NPOPs were applied to high-value conversion reactions of CO₂ with propargylic amines and terminal alkynes under mild reaction conditions. The carboxylative cyclization transformation of propargylic amine into 2-oxazolidinone and the carboxylation transformation of terminal alkynes into phenylpropiolic acid had the highest TOF values of 1125.1 and 90.9 h^-1, respectively. The Ag@NPOP-1 was recycled and used five times without any significant decrease in catalytic activity, showing excellent catalytic stability and durability.

Selectively Regulating Lewis Acid-Base Sites in Metal-Organic Frameworks for Achieving Turn-On/Off of the Catalytic Activity in Different CO2 Reactions

Regulating Lewis acid-base sites in catalysts to investigate their influence in the chemical fixation of CO₂ is significant but challenging. A metal-organic framework (MOF) with open metal Co sites, {(NH₂ Me₂ )[Co₃ (μ₃ -OH)(BTB)₂ (H₂ O)]⋅9 H₂ O⋅5 DMF}_n (1), was obtained and the results of the catalytic investigation show that 1 can catalyze cycloaddition of CO₂ and aziridines to give 99 % yield. The efficiency of the cyclization of CO₂ with propargyl amines is only 32 %. To improve the catalytic ability of 1, ligand XN with Lewis base sites was introduced into 1 and coordinated with the open Co sites, resulting in a decrease of the Lewis acid sites and an increase in the Lewis base sites in a related MOF 2 ({(NH₂ Me₂ )[Co₃ (μ₃ -OH)(NHMe₂ )(BTB)₂ (XN)]⋅8 H₂ O⋅4 DMF}_n ). Selective regulation of the type of active centers causes the yield of oxazolidinones to be enhanced by about 2.4 times, suggesting that this strategy can turn on/off the catalytic activity for different reactions. The catalytic results from 2 treated with acid solution support this conclusion. This work illuminates a MOF-construction strategy that produces efficient catalysts for CO₂ conversion.

Recyclable Oxofluorovanadate-Catalyzed Formylation of Amines by Reductive Functionalization of CO2 with Hydrosilanes

An efficient method has been developed for the reductive amination of CO₂ by using readily available and recyclable oxofluorovanadates as catalysts. Various amines are transformed into the desired N-formylated products in moderate to excellent yields at room temperature in the presence of phenylsilane. Mechanistic studies based on in situ infrared spectroscopy suggest a reaction pathway initiated through F-Si interactions. The activated phenylsilane allows for CO₂ insertion to produce phenylsilyl formate, which undergoes attack by the amine to generate the target product.

Conversion of CO2 to Heterocyclohexenol Carboxylic Acids through a Metal-Organic Framework Sponge

The conversion of CO₂ into high value-added chemical products is the focus of current scientific research. We make use of the specific porous structure of nanosized metal-organic frameworks (MOFs) loading the highly active yet metastable nano Cu₂O to catalyze the conversion of CO₂ into a series of high value-added bioactive pyridone/pyrone-3-carboxylic acid products via heterocyclic 4-hydroxy-2-pyridones/pyrones, which exhibit high activity, selectivity, and reusability. Nano MOF sponge-covered metastable nanoparticles (NPs) converting CO₂ into high value-added bioproducts provide a facile "dual-side surfactant" strategy, a highly efficient composite catalyst, and a practicable pathway not only for the sustainable use of CO₂ but also for environment-friendly production of bioproducts.

DNA intercalative trinuclear Cu(ii) complex with new trans axial nitrato ligation as an efficient catalyst for atmospheric CO2 fixation to epoxides

A trinuclear octahedral Cu^II complex was synthesized and structurally characterized by single crystal X-ray diffraction studies and behaved as a catalyst for CO₂ fixation to epoxide and as a DNA binder.