Cycloaddition Reaction Of CO2 Research Articles

Modified melamine-based porous organic polymers with imidazolium ionic liquids as efficient heterogeneous catalysts for CO2 cycloaddition

The chemical conversion of carbon dioxide (CO2) into highly value-added products not only alleviates the environmental issues caused by global warming but also makes an impact on economic benefits in the world. The synthesis of cyclic carbonates by the cycloaddition of CO2 with epoxides is one of the most attractive methods for CO2 conversion. However, the development of green and highly efficient heterogeneous catalysts is considered to be a great challenge in catalysis. In this work, alkenyl-modified melamine-based porous organic polymer (MPOP-4A) was firstly synthesized by a one-pot polycondensation method, and it was again modified with imidazolium-based ionic liquids to obtain final modified catalyst (MPOP-4A-IL). Various analytical techniques were used to confirm structure and chemical composition of the prepared materials. The MPOP-4A-IL catalyst synthesized by the post-modification strategy with imidazolium-based ionic liquids exhibited enhanced catalytic activity for CO2 cycloaddition reaction. The enhanced catalytic performance could be attributed to the presence of abundant active sites in their structure such as hydrogen bond donors (HBD), nitrogen (N) sites, and nucleophilic groups for an effective chemical reaction. The MPOP-4A-IL catalyst was found to be metal-free, easy to recycle and reuse, and has good versatility for a series of different epoxides. The interaction of MPOP-4A-IL catalyst with epoxide and CO2 was further verified by density functional theory (DFT) calculations, and the possible mechanism of the CO2 cycloaddition reaction was proposed.

Construction of Three-Dimensional Dendritic Hierarchically Porous Metal-Organic Framework Nanoarchitectures via Noncentrosymmetric Pore-Induced Anisotropic Assembly.

As a unique class of modular nanomaterials, metal-organic framework (MOF) nanoparticles have attracted widespread interest for use in various fields because of their diverse chemical functionalities, intrinsic microporosity, and three-dimensional (3D) nanoarchitectures. However, endowing MOF nanomaterials with precisely controlled structural symmetries and hierarchical macro/mesoporosities remains a formidable challenge for the researchers. Herein, we report a facile noncentrosymmetric pore-induced anisotropic assembly strategy to prepare a series of 3D dendritic MOF (UiO-66) nanomaterials with highly controllable structural symmetries and hierarchical macro/meso/microporosities. The synthetic route of these nanomaterials depends on the anisotropic nucleation of MOF spherical nanocones with noncentrosymmetric center-radial channels and their oriented growth to isotropic nanospheres through a continuous increase in radius and solid angle. This strategy enables the controllable fabrication of asymmetric MOF nanostructures with abundant geometries and porous structures by regulating the concentration of amphiphilic triblock copolymer templates. Furthermore, the average pore diameter of the resultant MOF nanospheres can be systematically manipulated in a wide range from 35 to 130 nm by finely tuning the reaction temperature. Meanwhile, the strategy can also be extended to synthesize other MOF nanoparticles with similar architectures. Compared with microporous UiO-66 nanocrystals, the MOF nanoparticles with controllable structural symmetries and macro/meso/microporosities show enhanced catalytic activity in the CO2 cycloaddition reaction. The methodology provides new insights into the rational construction of sophisticated asymmetric open nanostructures of hierarchically porous MOFs for many potential applications.

Facile Synthesis of Silicon-Based Materials Modified Using Zinc(Ⅱ) 2-Bromoacetic as Heterogeneous Catalyst for the Fixation of CO2 into Cyclic Carbonates

Much effort has been devoted to the development of efficient heterogeneous catalysts for the conversion of carbon dioxide (CO2) into high-value chemicals. Generally, the cycloaddition of CO2 to epoxides is considered a green and atom-economic reaction for the production of cyclic carbonates. Based on this, three kinds of silicon-based catalysts modified using zinc(Ⅱ) 2-bromoacetic (Si-ZnBA-n, n = 1, 2, 3) were facilely synthesized and employed for the chemical fixation of CO2 to epoxides with the use of potassium iodide (KI). A series of characterization techniques were used to characterize the textual structures and physicochemical properties of Si-ZnBA-n. The synergistic effects of Zn, –NH2, –OH and the nucleophilic group guaranteed the catalytic activity of Si-ZnBA-n. Si-ZnBA-1 exhibited the best catalytic activity among Si-ZnBA-n because Si-ZnBA-1 possessed the highest Zn content. Additionally, the effects of the reaction conditions (temperature, pressure, time and catalyst loadings) were also discussed. The propylene carbonate (PC) yield could reach 97% under 130 °C, 2 MPa, for 5 h without the employment of organic solvent, and its selectivity was 99%. In addition, the recycling property of Si-ZnBA-1/KI was also investigated, and the catalytic system exhibited good cycle performance. Meanwhile, the catalyst showed outstanding versatility for CO2 application to various epoxides, and a possibly synergistic reaction mechanism was proposed. Finally, a dynamic model was developed to discuss the activation energy of the CO2 cycloaddition reaction over the Si-ZnBA-1 catalyst.

Exploring the Effect of Different Secondary Building Units as Lewis Acid Sites in MOF Materials for the CO2 Cycloaddition Reaction.

In order to explore the catalytic effect of different Lewis acid sites (LASs) in the CO2 cycloaddition reaction, different secondary building units and N-rich organic ligand 4,4',4″-s-triazine-1,3,5-triyltri-p-aminobenzoate were assembled to construct six reported MOF materials: [Cu3(tatab)2(H2O)3]·8DMF·9H2O (1), [Cu3(tatab)2(H2O)3]·7.5H2O (2), [Zn4O(tatab)2]·3H2O·17DMF (3), [In3O(tatab)2(H2O)3](NO3)·15DMA (4), [Zr6O4(OH)7(tatab)(Htatab)3(H2O)3]·xGuest (5), and [Zr6O4(OH)4(tatab)4(H2O)3]·xGuest (6) (DMF = N,N-dimethylformamide, and DMA = N,N-dimethylacetamide). Large pore sizes of compound 2 enhance the concentration of substrates, and the multi-active sites inside its framework synergistically promote the process of the CO2 cycloaddition reaction. Such advantages endow compound 2 with the best catalytic performance among the six compounds and surpass many of the reported MOF-based catalysts. Meanwhile, the comparison of the catalytic efficiency indicated that Cu-paddlewheel and Zn4O display better catalytic performances than In3O and Zr6 cluster. The experiments investigate the catalytic effects of LAS types and prove that it is feasible to improve CO2 fixation property by introducing multi-active sites into MOFs.

Robust Fluorine-Functionalized {Ln5}-Organic Frameworks for Excellent Catalytic Performance on Cycloaddition of CO2 with Epoxides and Knoevenagel Condensation.

Lanthanide-organic frameworks (LnOFs) are a class of promising catalysts on a large number of organic reactions because of the higher coordination number of Ln3+ ions, inspired by which exploratory preparation of cluster-based LnOFs was carried out by us. Herein, the exquisite combination of spindly [Ln5(μ3-OH)6(CO2)6(H2O)6] clusters (abbreviated as {Ln5}) and fluorine-functionalized tetratopic ligand of 2',3'-difluoro-[p-terphenyl]-3,3″,5,5″-tetracarboxylic acid (F-H4PTTA) engendered two highly robust isomorphic nanoporous frameworks of {[Ln5(FPTTA)2(μ3-OH)6(H2O)6](NO3)}n (NUC-61, Ln = Ho and Dy). NUC-61 compounds are rarely reported {Ln5}-based 3D frameworks with nano-caged voids (19 Å × 17 Å), which are shaped by twelve [Ln5(μ3-OH)6(COO)8] clusters and eight completely deprotonated F-PTTA4- ligands. Activated NUC-61a compounds are characterized by plentiful coexisted Lewis acid-base sites of open LnIII sites, capped μ3-OH, and -F. Judged by the ideal adsorbed solution theory (IAST), activated NUC-61Ho-a had a high CO2/CH4 adsorptive selectivity with the value of 12.7 (CO2/CH4 = 50/50) and 9.1 (CO2/CH4 = 5/95) at 298 K, which could lead to high-purity CH4 (≥99.9996%). Furthermore, catalytic experiments exhibited that NUC-61Ho-a, as a representative, could efficiently catalyze the cycloaddition reactions of CO2 with epoxides as well as the Knoevenagel condensation reactions of aldehydes and malononitrile. This work proves that the {Ln5}-based skeletons of NUC-61 with chemical stability, heterogeneity, and recyclability are an excellent acid-base bifunctional catalyst for some organic reactions.

Cellulose nanofibers (CNF) supported (Salen)Cr(III) composite as an efficient heterogeneous catalyst for CO2 cycloaddition

For the simultaneous attainment of the utilization of renewable biomass resources and the mitigation of greenhouse effects, it is very promising to develop a green, recyclable, and highly efficient heterogeneous catalyst for the synthesis of cyclic carbonates by CO2 cycloaddition reaction with epoxides. Herein, novel cellulose nanofibers (CNF) supported (Salen)Cr(Ⅲ) complex was effectively synthesized for the aforementioned reaction. The cellulose nanofibers (CNF) were firstly modified with (3-aminopropyl) triethoxysilane (APTES), and then its Schiff base with salicylaldehyde was synthesized, which further subjected to coordination treatment with chromium chloride to form a novel heterogeneous catalyst, labelled as CNF-(Salen)Cr(Ⅲ). The catalytic performance of the catalysts shown that CNF-(Salen)Cr(Ⅲ) and co-catalyst TBAB can synergistically catalyze the cycloaddition of CO2 with epichlorohydrin (ECH) at mild reaction conditions, and the yield of chloropropene carbonate (CPC) reached up to 97.8% with high selectivity. The CNF-(Salen)Cr(Ⅲ) complex maintained high catalytic activity after six cycles of repeated runs and has acceptable catalytic effect on other series of epoxies. Based on density functional theory (DFT) calculations, a reaction mechanism including adsorption activation of epoxides, epoxides ring opening, CO2 insertion, and the formation of cyclic carbonate, was proposed for the CNF-(Salen)Cr(Ⅲ) complex catalyzed cycloaddition of CO2 with epoxides.

Theoretical study of supported ionic liquid membrane reaction and transport for CO2 cycloaddition reaction

Membrane reactors are promising for achieving a variety of thermodynamically limited reactions. However, few studies have focused on quantitative analysis of the coupling of reaction and separation matching of membranes. In this work, based on the experimental validation of the forced flow through principle of membrane reactors for catalytic CO2 cycloaddition, describes the membrane reaction performance of supported ionic liquid membranes (SILMs) in the presence of primary irreversible reactions, and draws on a dusty gas model to calculate fluxes within the gas pore space of the support. The degree of product separation is theoretically investigated in relation to the membrane permeation, the resistance difference between the ionic liquid membrane and the support, the liquid loading of the catalyst layer and the fluid flow rate, and adjustable parameters of the model are proposed to predict the SILM performance. In addition, two dimensionless numbers, namely Damköhler (Da) and Péclet (Pe) numbers, are introduced to correlate the equilibrium constant-conversion-DaPe relationship, and the reaction kinetics and permeate flux compatibility are analyzed with the help of CFD simulations, which incorporate parameters of operating conditions and stoichiometric coefficients of the reaction, as well as optimization of reactor geometrical, providing insights to achieve higher conversion improvements.

Hf/porphyrin-based metal-organic framework PCN-224 for CO2 cycloaddition with epoxides

Herein, we describe for the first time the synthesis of the highly porous Hf-tetracarboxylate porphyrin-based metal-organic framework (MOF) (Hf)PCN-224(M) (M = H2, Co2+). (Hf)PCN-224(H2) was easily and efficiently prepared following a simple microwave-assisted procedure with good yields (56–67%; space-time yields: 1100–1270 kg m−3·day−1), high crystallinity and phase purity by using trifluoromethanesulfonic acid and benzoic acid as modulators in less than 30 min. By simply introducing a preliminary step (10 min), 5,10,15,20-(tetra-4-carboxyphenyl)porphyrin linker (TCPP) was quantitatively metalated with Co2+ without additional purification and/or time consuming protection/deprotection steps to further obtain (Hf)PCN-224(Co). (Hf)PCN-224(Co) was then tested as catalyst in CO2 cycloaddition reaction with different epoxides to yield cyclic carbonates, showing the best catalytic performance described to date compared to other PCNs, under mild conditions (1 bar CO2, room temperature, 18–24 h). Twelve epoxides were tested, obtaining from moderate to excellent conversions (35–96%). Moreover, this reaction was gram scaled-up (x50) without significant loss of yield to cyclic carbonates. (Hf)PCN-224(Co) maintained its integrity and crystallinity even after 8 consecutive runs, and poisoning was efficiently reverted by a simple thermal treatment (175 °C, 6 h), fully recovering the initial catalytic activity.

The long-distance charge transfer process in ferrocene-based MOFs with FeO6 clusters boosts photocatalytic CO2 chemical fixation

Metal nodes and organic ligands are important structural units of MOFs, and their properties can profoundly affect the photocatalytic activity. Herein, two ferrocene-based MOFs with FeO6 or AlO6 clusters as the metal nodes and 1,1′-ferrocenedicarboxylic acid (H2FcDC) as the ligands were successfully synthesized. Comparing with normal organic ligands, ferrocene ligands have longer-lived photogenerated charges due to metal-to-ligand charge transfer (MLCT) process, leading to a better photocatalytic activity of the corresponding ferrocene-based MOFs. In addition, the FeO6 clusters are able to further accept the photogenerated electrons from ferrocene ligands compared to the inert AlO6 clusters, allowing a long-distance charge transfer process, namely the proposed metal-to-ligand-to-metal charge transfer (MLMCT) process, which results in a better performance towards photocatalytic CO2 cycloaddition reaction. This work sheds a light on designing MOFs using ferrocene ligands with high photocatalytic activity.

Robust Zn(II)-Organic Framework for High Catalytic Activity on Cycloaddition of CO2 with Epoxides and Reversible Iodine Uptake

Increasingly serious natural disasters caused by excessive CO2 emission have given birth to a series of carbon-neutral technologies, among which the chemical transformation of CO2 catalyzed by metal–organic framework (MOF)-based catalysts has become a focus. Herein, the self-assembly of zinc(II) cation and designed flexible multifunctional ligand of 1,3-di(5,6-dicarboxylbenzimidazol-1-ylmethyl)benzene (H4DDBB) generated a highly robust microporous material of {[Zn(H2DDBB)]·2NMP}n (NUC-69) with 1D rectangle open channels (10.0 × 7.6 Å2). Because the inner wall of voids is densely functionalized by free −COOH groups, Nimidazole atoms, and tetra-coordinated open metal sites, activated NUC-69a exhibits high catalytic performance on the cycloaddition reactions of CO2 with epoxides under mild conditions with high turnover number and turnover frequency. In addition, NUC-69a can be used as an efficient iodine adsorbent with a maximum adsorption capacity of 0.94 g/g (4.26 I2 molecules per formulation unit) and 1.28 g/g (5.81 I2 molecules per formulation unit) in hexane solution and the volatilization phase. Hence, this work provides a productive insight into the design of multifunctional microporous MOFs by enhancing the types of active sites, which makes the developed materials a broader application prospect.

Multi-dimensional application of quaternary phosphonium salt functionalized fiber with high polarization performance: Efficient adsorption of SDBS and green conversion of CO2

A novel mono-quaternary phosphorus salt functionalized fiber (PANQPSF) was developed as the multifunctional material to simultaneously realize selective removal of sodium dodecyl benzene sulfonate (SDBS) from water and green conversion of CO2. Compared with other adsorption materials and functionalized fibers, PANQPSF exhibits the eminent adsorption performance for SDBS due to its high polarization and hydrophobicity, and the adsorption capacity can reach 5.1 mol mol−1, equivalenting to 1066 mg g−1. And the synergistic adsorption mechanism of electrostatic interaction and lipophilic interaction between PANQPSF and SDBS is proposed. Furthermore, the PANQPSF still keeps excellent adsorption capacity even after 10 cycles. More satisfactorily, PANQPSF is used to catalyze the cycloaddition reaction of CO2 and epoxy compounds. The catalytic mechanism based on the nucleophilicity of Br− and the stabilizing effect of electrostatic interaction is promoted. In summary, the adsorption and catalytic performance prove that PANQPSF is an outstanding material with multi-dimensional applications.

Post-synthetic modification of Zr-MOFs using guanidine for cyclic carbonate formation catalysis

A post-synthetic modification of Zr-MOF using ionic nitrogen-based functional groups is proposed for the catalytic cycloaddition reaction of CO2 with epoxides. Herein, guanidinium salt derivatives are used as ionic liquid (IL) catalysts while MOFs are used as a superior absorbent for CO2, allowing the generation of heterogeneous catalysts for CO2 fixation reactions under mild conditions. The UiO66-NH2 and UiO67-NH2 were functionalized with carbodiimides N,N′-dicyclohexylcarbodiimide (DCC) and N,N′-diisopropylcarbodiimide (DIC) to produce cationic guanidinium-containing Zr-MOFs with free bromide ions UiO66-DCCBr, UiO66-DICBr, and UiO67-DICBr. The materials were characterized comprehensively by multiple techniques such as PXRD, FTIR, TGA, SEM, EDS, 1H NMR, 13C NMR, elemental analysis, as well as N2 and CO2 adsorption equilibrium measurements. UiO66-DCCBr showed a high TOF for the formation of cyclic carbonates using several small epoxides under mild conditions (0.5 MPa CO2, 90 °C, without co-catalyst and solvent). In addition, UiO67- DICBr owing to the larger aperture size of MOF displayed better catalytic performance for the conversion of larger epoxides than UiO66-DICBr and UiO66-DCCBr with high yield and selectivity. This result underlines the important role of MOF’s aperture size for the diffusion of substrates in CO2 fixation reactions.

A tetranuclear Er(III)-based cluster with bifunctional properties: Efficient conversion of CO2 and slow magnetic relaxation behavior

A new Er4 cluster [Er4(NO3)2(acac)4(L)2(CH3OH)2]·2CH3CN (1) (H4L = (E)-2-(hydroxymethyl)-2-(((2-hydroxynaphthalen-1-yl)methylene)amino)propane-1,3-diol, and Hacac = acetylacetone) were synthesized by employing a polydentate Schiff-base ligand (H4L) and a β-diketonate co-ligand and further characterized structurally. Alternating current (ac) magnetic susceptibility measurements indicated that cluster 1 shows slow relaxation of magnetization behavior. More importantly, cluster 1 shows high catalytic activity of the cycloaddition reaction of CO2 and epichlorohydrin under mild conditions; and cluster 1 as heterogenous catalyst can be reused at least three times without any obvious loss in catalytic activity. It is worth mentioning that cluster 1 is a rare bifunctional Ln(III)-based material for both molecular based magnetic material and heterogenous catalyst.

A series of bifunctional metalloporphyrins as efficient catalysts for cycloaddition of CO2 with epoxides

Two porphyrins, named H2TEtImP and H2DEtImP, with the four and two N‐ethylated imidazole groups, respectively, as well as their metalloporphyrins, M‐TEtImP (M = Zn, Mn, Co, Mg) and Zn‐DEtImP, were synthesized and characterized by ultraviolet–visible (UV–Vis), mass spectrometry (MS), proton nuclear magnetic resonance (1H NMR), and Fourier transform infrared (FTIR) successfully. The catalytic activity of these newly synthesized porphyrins with metal centers and halogen ions as variables on the cycloaddition reaction between carbon dioxide (CO2) and epoxides was investigated under solvent‐free conditions. The experimental results strongly verified that both halogen ions and metal centers were indispensable active sites. The metal catalytic activity increased in the order Co < Mn < Mg < Zn. The turnover frequency (TOF) of Zn‐TEtImP for the cycloaddition reaction of CO2 and epichlorohydrin was as high as 2213 h−1 (120°C, 1 MPa CO2, 6 h). Moreover, the wide applicability of Zn‐TEtImP to this reaction was demonstrated by substrate extension experiments, and the excellent recyclability of Zn‐TEtImP was confirmed. Finally, the synergistic catalytic mechanism of Lewis acid (metal center) and nucleophile (Br−) was proposed based on the catalytic results.

One-pot efficient fixation of low-concentration CO2 into cyclic carbonate by mesoporous pyridine-functionalized binuclear poly(ionic liquid)s

The direct conversion of low-concentration CO2 from flue gas avoids the energy-intensive purification and concentration of CO2 to implement the next utilization, making it undoubtedly a green process. However, achieving low-concentration CO2 cycloaddition with epoxide over functional poly(ionic liquid) catalysts and understanding the relevant mechanism at the molecular level is still challenging. Here, novel mesoporous pyridine-functionalized binuclear poly(ionic liquid)s (PB-PIL)s were successfully synthesized by the polymerization of DVB, basic monomers, and binuclear ionic liquid monomers, regulating the density of pyridine sites and binuclear halogen counterions to achieve the optimum balance between the active sites and pore structure of copolymerized materials. Remarkably, PB-PILs were active in the cycloaddition reaction of the low-concentration CO2 (15% CO2 + 85% N2) without any co-catalyst and gave a 95% yield of cyclic carbonate. Relied on DFT theoretical calculation, the activation degree of pyridine to CO2 and the promotion of CO2 insertion were deeply explored, providing more broad ideas for the conversion of low-concentration CO2.

Simultaneous Activation of Carbon Dioxide and Epoxides to Produce Cyclic Carbonates by Cross‐linked Epoxy Resin Organocatalysts

AbstractThe development of efficient bifunctional organocatalysts for the catalytic conversion of CO2under mild conditions remains particularly challenging. Inspired by the synergistic mechanism of intramolecular Lewis acid‐base active sites, we report a series of bifunctional cross‐linked epoxy resin organocatalysts containing multiple active sites for the cycloaddition reaction of dilute CO2with epoxides. These catalysts exhibit high reactivity and product selectivity (10 examples, >99 %) for the cycloaddition reactions of a variety of epoxides and CO2, and surprisingly, epichlorohydrin (ECH), can be converted under ambient temperature and pressure (25 °C, 1.0 bar) without co‐catalysts.1H NMR,13C NMR,19F NMR and in situ IR studies suggest that the simultaneous and efficient activation of CO2and epoxides is responsible for the improved catalytic activity. Upon an insightful investigation of the catalytic mechanism, this protocol will contribute to the development of efficient and environmentally friendly metal‐free catalysts.

POSS-based ionic polymer catalyzed the conversion of CO2 with epoxides to cyclic carbonates under solvent- and cocatalyst-free conditions at ambient pressure

A series of polymers are simply synthesized by the copolymerization of vinyl functionalized polyhedral oligomeric silsesquioxanes (POSS) with vinylimidazole based linker by modulating the molar ratio of two monomers. The synthesized POSS-based polymers are capable of catalyzing the cycloaddition reaction of CO2 with a variety of epoxides at atmospheric pressure without solvent and co-catalyst, producing cyclic carbonates with conversion up to 97.1 %. Noteworthy, the reaction kinetics studies have demonstrated that the POSS-based polymers are able to significantly reduce the activation energy of cycloaddition reactions of CO2. In addition, as a heterogenerous catalysts, the POSS-based polymer can be recovered and recycled 5 times without reducing catalytic performance.

Effect of exposed active sites of semi-amorphous Fe-BTC on photocatalytic CO2 cycloaddition reaction under ambient conditions

The capture and efficient use of CO2 is an important issue because CO2 emissions by burning fossil fuels is a primary cause of greenhouse effect. One of the best solutions to this problem is to convert CO2 into valuable organic products through clean technologies. In this work, semi-amorphous material Fe-BTC with highly efficient photocatalytic CO2 cycloaddition reactions was prepared by adopting two strategies: the coordination of Fe ions with H2BDC affected by different solvents and the defect engineering controlled by relatively low temperatures. Combined with FT-IR, SEM, TGA and BET analysis, the two strategies change the properties of Fe-BTC to a certain extent. The NH3-TPD analysis confirmed that the Fe-BTC prepared in different solvents and temperatures had different number of Lewis acid sites, and more Lewis acid sites were beneficial to improve the yield of the reaction. In addition, DFT theoretical calculation also verified that the defective Fe-BTC obtained by relatively low temperature would expose more active sites. Finally, light also played an irreplaceable role in this reaction, as photogenerated charge carriers produced under light excitation could greatly activate CO2 and epoxides, thereby reducing the energy barrier of the reaction. Based on the above photocatalytic experimental results and characterization, the possible mechanism was proposed and explained. This work would provide an economical and effective strategy to obtain more active sites for CO2 cycloaddition reaction under mild conditions.

Intramolecular synergistic catalysis of ternary active sites of imidazole Ionic-liquid polymers immobilized on nanosized CoFe2O4@polystyrene composites for CO2 cycloaddition

The cycloaddition reaction of CO2 with epoxides is challenging, thereby requiring the development of environmentally friendly catalysts. Herein, a strategy was developed to construct a multifunctional heterogeneous magnetic catalyst (MPNPs-[ImR2NH2][ZnBr3]) of aminoethyl imidazole metal halide ionic liquids coated on nano-sized CoFe2O4@polystyrene for CO2 cycloaddition. The created catalytic system displayed the intramolecular synergy of ternary active sites (Zn2+, Br−, and –NH2), as well as coupling of catalysis and magnetic separation. In the absence of co-catalyst and solvent, MPNPs-[ImR2NH2][ZnBr3] exhibited excellent catalytic performance for CO2 cycloaddition (99.92% yield and 100% selectivity) at 120 ℃ with 0.16 mol% catalyst dosage in 2.5 h. By appropriately increasing the reaction duration and catalyst dosage, 98.83% conversion and 99.26% selectivity were achieved even at mild conditions of 60 °C and 0.1 MPa. After 10 cycles of reuse, the recycled MPNPs-[ImR2NH2][ZnBr3] demonstrated the same high-efficiency activity as the fresh catalyst, as well as excellent stability and magnetic separation. Based on the density functional theory (DFT) calculations, the intramolecular synergy of ternary active sites and the catalytic mechanism of bimolecular activation based on the multifunctional structure were proposed. This excellent catalyst was attributed to the intramolecular synergy of ternary active sites, large loading of active centers, lower internal diffusion resistance, the inert protective effect of polystyrene layer and the easily magnetic separation of CoFe2O4, highlighting a new direction for green catalytic chemistry.

A Luminescent Zinc(II) Coordination Polymer for Selective Detection of Fe3+ and Cr2O72− in Water and Catalytic CO2 Fixation

AbstractFluorescence‐based detection technique using coordination polymer has been considered an attractive alternative over conventional approaches. Herein, a new luminescent zinc(II) coordination polymer, [Zn(4‐ABPT)(NIPA)(H2O)], SSICG‐5, is synthesized by using a Lewis acidic Zn(II) ion, aromatic nitro group containing ligand 5‐nitroisophthalic acid (H2NIPA), and basic −NH2 rich ligand 3,5‐di(pyridine‐4‐yl)‐4H‐1,2,4‐triazol‐4‐amine (4‐ABPT). SSICG‐5 can detect Fe3+ and Cr2O72− selectively with a LOD of 0.16 μM and 1.94 μM, respectively. Additionally, carbon dioxide (CO2) fixation via one‐pot CO2 cycloaddition reaction has significant importance for reduced waste formation, minimizing reaction time and lowering chemical usage. Zn metal centre of SSICG‐5 possesses a replaceable coordinated water molecule. The active metal sites combined with the Lewis acidic and basic sites of the ligands make SSICG‐5 an ideal bifunctional heterogeneous catalyst for efficient CO2 cycloaddition reaction under room temperature (RT), solvent‐free conditions. Notably, SSICG‐5 exhibits near quantitative conversion (turnover number (TON) of 198) of propylene oxide to its carbonate compound under mild reaction conditions.