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Iron(III) bis(phenol) amine complex immobilized on the surface of functionalized graphene oxide nanosheets (FeLGDC‐AP/GO) has introduced as a highly active and recoverable catalyst for the epoxidation of alkenes. Optimizing different parameters in the oxidation of styrene as a model substrate revealed that 100% conversion and selectivity were obtained toward styrene oxide in the presence of H2O2 (28 wt%) as oxidant and water/acetone (3:1) as a solvent system in a bicarbonate buffer system. Furthermore, the catalyst displayed 54%–100% conversion and 90%–100% selectivity for the epoxidation of various aromatic and aliphatic alkenes under optimized reaction conditions at room temperature. The recycling experiment showed that FeLGDC‐AP/GO could be easily recovered by simple filtration and recycled six times without loss of the activity and selectivity. The high catalytic activity and selectivity of the developed catalyst could be attributed to the well‐designed coordination sphere around the iron core as well as the presence of GO support, which facilitates the electron transfer process beside the catalyst recovery. [ABSTRACT FROM AUTHOR]

Developing efficient carbon dioxide (CO2) capture and conversion methods is vital for climate change mitigation. Cycloaddition of CO2 with epoxides to form cyclic carbonates is a promising utilization method. In this study, a deep eutectic solvent‐modified dendritic fibrous nano‐silica (DES@DFNS) catalyst was synthesized by functionalizing DFNS with DES. This catalyst was used for the cycloaddition of CO2 with styrene oxide to produce styrene carbonate. The material's morphology and properties were characterized using various analytical techniques, revealing a high surface area, good porosity, and significant concentrations of Lewis acidic and basic sites. Rietveld refinement analysis provided insights into its phase composition, crystallite size, microstrain, stress, and other microstructural properties. Despite a lower surface area, DES@DFNS demonstrated superior catalytic activity. The interaction between DES and DFNS showed that DES was physically adsorbed onto the DFNS surface, contributing to its enhanced performance. Factors such as smaller crystallite size, higher microstrain, increased dislocation density, and improved elastic properties provided more active sites and greater mechanical stability, boosting overall efficiency and durability. The DES@DFNS catalyst achieved 99% conversion of styrene oxide with 96% selectivity and 95% yield of styrene carbonate at 120 °C for 10 h under solvent‐free, atmospheric conditions. The synergistic effect of Lewis acidic and basic sites on DES@DFNS supported catalytic activity under moderate conditions. Additionally, the catalyst demonstrated reusability, maintaining performance for up to six cycles without significant loss of activity, making it a promising candidate for sustainable CO2 fixation and valorization processes. [ABSTRACT FROM AUTHOR]

'On‐water' catalysis entails the significant enhancement of a chemical reaction by water, even when those reactions are known to be water‐sensitive. Here, the findings about the anionic ring opening polymerization of epoxides at the static interface between oil and alkaline water are shared. Unexpectedly, high molar mass fractions are observed with the interfacial system presented herein, albeit at very low conversions (< 5%). Styrene oxide, a notably unreactive epoxide, is chosen as the model compound to investigate the influence of several reaction parameters (i.e., pH, type of the initiator salt, polymerization time, interfacial area, solvent, shaking) on the polymerization. Poly(styrene oxide) (PSO) with an Mn of 5300 g mol−1 is observed via MALDI‐ToF MS, with species of at least 8000 g mol−1. The feasibility of expanding the system to (cyclic) aliphatic and aromatic epoxides, and glycidyl ethers is also explored. The system appears to promote polymerization of epoxides that position at the interface, in such a way that initiation and propagation can occur. A mechanistic interpretation of the interfacial polymerization is suggested. The surprising results obtained in this work urge to revisit the role of water in ionic polymerizations. [ABSTRACT FROM AUTHOR]

New chloride‐ and bromide‐modified metal–organic frameworks (MOFs) based on copper and 1,3‐bis (carboxymethyl)imidazole (bcmim) derivatives have been prepared via post–synthetic modification (PSM) or by a direct route, following a simple, effective, and sustainable protocol. These materials have been characterized, and their catalytic activity has been studied. Cu‐bcmim‐Cl and Cu‐bcmim‐Br materials have been shown to be more efficient acidic catalytic systems than nonmodified materials. The catalytic activity has been tested as a Lewis acid catalyst in the methanolysis of styrene oxide and in the synthesis of quinolines and acridines, with the recovery and recyclability of the catalysts being possible. Furthermore, the catalytic activity of the catalysts has been tested in the oxidative coupling of formamides and carboxylic acids. [ABSTRACT FROM AUTHOR]

Tetradentate ONNO donor ligands H2hz(fp)2 (I), H2hz(butp)2 (II) and H2hz(bp)2 (III) synthesized by the reaction of hydrazine hydrate with 4‐formyl‐3‐methyl‐1‐phenyl‐5‐pyrazolone (fp), 4‐butyryl‐3‐methyl‐1‐phenyl‐5‐pyrazolone (butp) and 4‐benzoyl‐3‐methyl‐1‐phenyl‐5‐pyrazolone (bp), respectively, react with [MoVIO2(acac)2] in 1 : 2 molar ratio in refluxing methanol to give binuclear complexes [(μ‐O){MoVIO2(H2O)}2hz(fp)2] (1) and [(μ‐O){MoVIO2(H2O)}2hz(butp)2] (2) and [(μ‐O){MoVIO2(H2O)}2hz(bp)2] (3). All ligands and complexes are characterized by several techniques that include, FT‐IR, UV/Vis, 1H NMR, 13C NMR spectroscopy, elemental and thermal analysis, and single crystal X‐ray analysis of 2 and 3. Ligands coordinate through a set of ON functionalities of the same ligand to two MoVIO2 groups attached through an oxido‐bridge. Additional coordination of water to each vanadium makes each of them to maintain an octahedral geometry. Azine moiety coordinates to two molybdenum through the symmetrical μ‐{η2‐(N−N)} fashion. Catalytic activity of these complexes was studied for the cycloaddition of CO2 with epoxides. A pressure of 4 bar CO2, 3.0 mg catalyst, 1 mmol of tetrabutylammonium bromide (TBAB) at 120 °C for 6 h were found to be most suited reaction condition for 10 mmol epoxide. Under the optimized reaction conditions, the product yield and selectivity of alkene carbonate for all complexes were investigated. As high as 96 % yield with almost 99 % selectivity for styrene carbonate under these optimized reaction conditions was achieved. [ABSTRACT FROM AUTHOR]

The epoxidation of olefins on Ag/O systems is a significant industrial‐scale process within heterogeneous catalysis. However, the details of the surface reaction remain controversial, and it has been highly challenging to reconcile the findings from cataltyic studies under reaction conditions with the highly detailed static studies under carefully controlled ultra‐high vacuum (UHV) conditions. In this study, we combine molecular beam surface scattering and ion imaging techniques to explore the partial oxidation of styrene. This experimental approach enhances the sensitivity to the extent that we can directly observe the partial oxidation product, styrene oxide, under UHV conditions. We note that partial oxidation exclusively occurs at high oxygen coverages, which we attribute to the reaction of styrene with electrophilic oxygen formed specifically at elevated coverages. [ABSTRACT FROM AUTHOR]

The conventional synthesis of (S)‐flurbiprofen, a valuable non‐steroidal anti‐inflammatory drug (NSAID), involves inefficient chiral resolution with low‐yielding multiple reaction steps, or asymmetric synthesis with low enantioselectivity and/or regioselectivity. Here, we developed high‐yielding, enantioselective, and sustainable synthesis of (S)‐flurbiprofen via two chemoenzymatic approaches from a simple alkene: (A) enzymatic epoxidation‐isomerization‐oxidation cascade and Pd‐catalyzed arylation; and (B) chemical epoxidation, enzymatic isomerization‐oxidation cascade, and Pd‐catalyzed arylation. Styrene oxide isomerase (SOI)‐catalyzed enantio‐retentive Meinwald rearrangement was the key step in the two pathways, but SOI suffers from low activity. SOI was engineered via two rounds of iterative saturation mutagenesis and screening with a three‐enzyme cascade assay, generating a double‐mutant SOIDM (N99A/D95A) with 5.5‐fold improvement in catalytic efficiency (kcat/KM). In Pathway A, cascade biotransformation of 3‐fluoro‐4‐bromo‐α‐methylstyrene with engineered E. coli strain expressing SOIDM, styrene monooxygenase (SMO) and aldehyde dehydrogenase (ALDH), and subsequent Pd‐catalyzed arylation afforded (S)‐flurbiprofen in 98% yield and 91% ee. In Pathway B, chemical epoxidation (Sharpless dihydroxylation and ring‐closing), cascade conversion using an engineered E. coli strain expressing SOIDM, ALDH and NADH oxidase (NOX), and Pd‐catalyzed arylation produced (S)‐flurbiprofen in 83% yield and 98% ee. Compared to conventional synthesis, the developed methods reduced reaction steps, minimized waste generation and improved enantioselectivity or overall yield. [ABSTRACT FROM AUTHOR]

The redox mediated photoelectrochemical (PEC) or electrochemical (EC) alkene oxidation process is a promising method to produce high value‐added epoxides. However, due to the competitive reaction of water oxidation and overoxidation of the mediator, the utilization of the electricity is far below the ideal value, where the loss of epoxidation's faradaic efficiency (FE) is ≈50%. In this study, a Br−/HOBr‐mediated method is developed to achieve a near‐quantitative selectivity and ≈100% FE of styrene oxide on α‐Fe2O3, in which low concentration of Br− as mediator and locally generated acidic micro‐environment work together to produce the higher active HOBr species. A variety of styrene derivatives are investigated with satisfied epoxidation performance. Based on the analysis of local pH‐dependent epoxidation FE and products distribution, the study further verified that HOBr serves as the true active mediator to generate the bromohydrin intermediate. It is believed that this strategy can greatly overcome the limitation of epoxidation FE to enable future industrial applications. [ABSTRACT FROM AUTHOR]

The redox mediated photoelectrochemical (PEC) or electrochemical (EC) alkene oxidation process is a promising method to produce high value‐added epoxides. However, due to the competitive reaction of water oxidation and overoxidation of the mediator, the utilization of the electricity is far below the ideal value, where the loss of epoxidation's faradaic efficiency (FE) is ≈50%. In this study, a Br−/HOBr‐mediated method is developed to achieve a near‐quantitative selectivity and ≈100% FE of styrene oxide on α‐Fe2O3, in which low concentration of Br− as mediator and locally generated acidic micro‐environment work together to produce the higher active HOBr species. A variety of styrene derivatives are investigated with satisfied epoxidation performance. Based on the analysis of local pH‐dependent epoxidation FE and products distribution, the study further verified that HOBr serves as the true active mediator to generate the bromohydrin intermediate. It is believed that this strategy can greatly overcome the limitation of epoxidation FE to enable future industrial applications. [ABSTRACT FROM AUTHOR]

Developing efficient and earth‐abundant catalysts for CO2 fixation to high value‐added chemicals is meaningful but challenging. Styrene carbonate has great market value, but the cycloaddition of CO2 to styrene oxide is difficult due to the high steric hindrance and weak electron‐withdrawing ability of the phenyl group. To utilize clean energy (such as optical energy) directly and effectively for CO2 value‐added process, we introduce earth‐abundant Ti single‐atom into the mesoporous nitrogen, oxygen‐doped carbon nanosheets (Ti−CNO) by a two‐step method. The Ti−CNO exhibits excellent photothermal catalytic activities and stability for cycloaddition of CO2 and styrene oxide to styrene carbonate. Under light irradiation and ambient pressure, an optimal Ti−CNO produces styrene carbonate with a yield of 98.3 %, much higher than CN (27.1 %). In addition, it shows remarkable stability during 10 consecutive cycles. Its enhanced catalytic performance stems from the enhanced photothermal effect and improved Lewis acidic/basic sites exposed by the abundant mesopores. The experiments and theoretical simulations demonstrate the styrene oxide⋅+ and CO2⋅− radicals generated at the Lewis acidic (Tiδ+) and basic sites of Ti−CNO under light irradiation, respectively. This work furnishes a strategy for synthesizing advanced single‐atom catalysts for photo‐thermal synergistic CO2 fixation to high value products via a cycloaddition pathway. [ABSTRACT FROM AUTHOR]

Phenylacetaldehyde (PhA) is an aromatic aldehyde which has a hyacinth‐like floral, sweet and green‐leafy odour. PhA is used as a perfumery chemical and a rate‐controlling additive in cosmeceutical and polymer industries, respectively. The conventional process of PhA manufacturing in industries involve hazardous and costly feedstock and often lead to generation of substantial amount of waste. Moreover, usage of stoichiometric reagents often makes the processes economically impractical. This article illustrates the possibility of production of PhA from low‐cost feedstock styrene through a single‐step, one‐pot method wherein various metal oxides have been utilized as catalysts for styrene oxidation under the influence of cumene hydroperoxide (CHP). Ag2O is found to be the highest PhA‐yielding catalyst and a promising candidate for scaling up for its considerably good reusability up to 6 consecutive uses. A maximum of ~45% PhA selectivity has been observed at ~60% styrene conversion. Interestingly, this process does not require any alkaline/acid wash and hence does not produce any organic/inorganic liquid effluent stream. Furthermore, all the major byproducts found, that is styrene oxide, benzaldehyde and acetophenone, are themselves considered as valorized styrene derivatives. Overall, the metal oxide catalysed styrene oxidation has potential to take over the conventional industrial process(es) for sustainable selective production of PhA Along with a plausible mechanism of styrene oxidation over Ag2O, a conceptualized reaction–separation framework has been reported for intensified production of PhA from CHP‐based styrene oxidation. [ABSTRACT FROM AUTHOR]

Nanoconfinement within enzymes can increase reaction rate and improve selectivity under mild conditions. However, it remains a great challenge to achieve chemical reactions imitating enzymes with directional molecular motion, short reaction time, ≈100% conversion, and chiral conversion in artificial nanoconfined systems. Here, directional flow ring‐opening reactions of styrene oxide and alcohols are demonstrated with ≈100% conversion in <120 s at 22 °C using graphene oxide membrane nanoreactors. Dominant products have the same configuration as chiral styrene oxide in confined reactions, which is dramatically opposed to bulk reactions. The unique chiral conversion mechanism is caused by spatial confinement, limiting the inversion of benzylic chiral carbon. Moreover, the enantiomeric excess of same‐configuration products increased with higher alkyl charge in confined reactions. This work provides a new route to achieve rapid flow ring‐opening reactions with specific chiral conversion within 2D nanoconfined channels, and insights into the impact of nanoconfinement on ring‐opening reaction mechanisms. [ABSTRACT FROM AUTHOR]

Developing a highly efficient and environmentally friendly catalytic system for CO2 cycloaddition reactions is an attractive way to achieve carbon neutrality. In this work, tetrabutylammonium iodide (TBAI) and polyethylene glycol (PEG) were used to produce novel deep eutectic solvents (DESs), which could serve as both solvents and catalysts, displaying excellent activity to synthesis styrene carbonates from CO2 and styrene oxide under metal‐free, cocatalyst‐free, solvent‐free and mild conditions. A detailed study was undertaken on the effects of reaction parameters, recyclability, and substrate scope. Additionally, the H‐bond interaction between the substrate and TBAI/PEG200 was thoroughly investigated using FT‐IR and 1H NMR techniques. The synergistic interaction between the two components of the DES, TBAI, and PEG200, may be the key to the high catalytic activity of this system. The tetrabutylammonium iodide‐based system is an innovative strategy for the CO2 cycloaddition with epoxides, achieved by elaborately devising the H‐bonds of DESs to enhance reactivity. This provides a novel green strategy for potential industrial applications. [ABSTRACT FROM AUTHOR]

Precise design of highly efficient, low metal load and eco‐friendly catalysts is the key to sustainable catalysis and green chemistry. In this work, we develop an ultra‐low loading of Mn(salen) complexes covalent grafted with lignin and applied in the selective epoxidation of olefins using O2 as an oxidant. Lignin not only provides the Mn(salen) graft sites but also promotes substrate enrichment via the π‐stacking interaction between substrate and supports. In particular, high turnover frequencies (TOF) of 1833 h−1 can be obtained for styrene epoxidation under mild conditions, which can be superior to most reported Mn(salen) supported catalysts. Compared with cellulose, the lignin‐based catalysts exhibit a higher selectivity toward styrene oxide during the epoxidation of styrene under mild conditions. Controlled experiments indicate that the synergistic effect between phenolic hydroxyl groups and the Mn(salen) complex can improve the conversion rate and selectivity during the selective epoxidation of styrene. This work designs a series of lignin‐based catalysts with ultra‐low Mn(salen) loading, which broadens the utilization of lignin and gives enlightenment for the rational design of lignin‐based catalysts. [ABSTRACT FROM AUTHOR]

Application of a binary Ga‐based catalyst system for the coupling of CO2 and aziridines to form oxazolidinones is presented. It has been possible to optimize the catalyst system for the selective formation of a single regioisomer, in excellent yield, under relatively mild reaction conditions. The optimized catalyst system has been successfully applied to a range of substituted aziridines derived from styrene oxide. It has been observed that aziridines bearing two aromatic substituents result in piperazine formation through an unexpected dimerization reaction. These piperazine products can be selectively formed in the absence of CO2 or are favored at lower reaction temperatures. A detailed DFT study into the reaction mechanism for the formation of both products has been carried out and an unusual ligand assistance in the case of oxazolidinone synthesis has been identified. More specifically, this ligand interaction promotes the initial ring‐opening of the aziridine and this work presents the first fully elucidated mechanism involving this intermediate. [ABSTRACT FROM AUTHOR]

Introducing organic groups into metal silicate catalysts and thus supposedly changing the surface hydrophobicity has been shown to enhance the catalyst performance in various reactions. However, the organic groups introduction does not unambiguously guarantee hydrophobicity control. Therefore, a thorough characterization is necessary to provide a complete view of the interaction between the catalyst surface, reactants, and products. Herein, an aluminosilicate catalyst with well‐dispersed Al atoms was prepared via the non‐hydrolytic sol‐gel method. This material was post‐synthetically modified with trimethylsilyl groups; their number on the catalyst surface was controlled via a temperature‐vacuum pretreatment. In such a way, aluminosilicate materials with similar porosity, structure, and acid site strength and quality were obtained. Notably, the water sorption measurements showed that trimethylsilylated aluminosilicates adsorb 2.5–3 times less water than the parent material (p/p0=0.3). The turn‐over‐frequency in epoxide ring opening and ethanol dehydration scaled up with the number of trimethylsilyl groups grafted on the catalyst surface. Particularly, the heavily trimethylsilylated sample achieved three to five times higher turnover‐frequency in styrene oxide aminolysis than the parent aluminosilicate material. To the best of the authors' knowledge, it exhibited the most active Al sites for epoxide aminolysis in the present literature. [ABSTRACT FROM AUTHOR]

A new biocatalyst MP8@MIL‐101(Cr/Fe) was prepared by immobilization of a heme octapeptide, Microperoxidase 8 (MP8) within a mixed metal MOF, MIL‐101(Cr/Fe). Both MIL‐101(Cr/Fe) and MP8@MIL‐101(Cr/Fe) were characterized by PXRD, FTIR spectroscopy and TGA. The catalytic activity of MP8@MIL‐101(Cr/Fe) for the oxidation of styrene by H2O2 and tBuOOH was then examined under various reaction conditions (nature of the co‐solvent and of the oxidant, concentration of the oxidant and of the substrate, time, pH) and compared to that of MP8 alone. Under the best conditions used, MP8@MIL‐101(Cr/Fe) was then shown to catalyze the oxidation of styrene about 3 times more efficiently than MP8 alone with approximately 50 % selectivity for styrene oxide. [ABSTRACT FROM AUTHOR]

A series of benzoylacetone‐imine ligands, PhCOCHCMeNHR (L1H, R = CH2Ph; L2H, R = CH2Ph‐4‐Me; and L3H, R = CH2Ph‐4‐OMe), are first synthesized following the condensation of benzoylacetone and 4‐substituted benzylamine. Later, reacting L1H–L3H with one equivalent of AlMe3 in toluene, the monomeric Al derivatives are generated, (PhCOCHCMeNR)AlMe2 (1, R = CH2Ph; 2, R = CH2Ph‐4‐Me; 3, R = CH2Ph‐4‐OMe). All the ligands and metal derivatives are characterized by 1H and 13C NMR spectroscopy. Single crystal X‐ray diffraction analysis reveals the geometry of all ligands and complex 2. As supporting catalysts, the Al derivatives, 1–3, are effective to initiate the coupling of CO2 and styrene oxide to form cyclic carbonates. Although employing TBAI (tetra‐n‐butylammonium iodide), TBAC, tetrabutylammonium chloride, and TBAB (tetra butyl ammonium bromide) as cocatalyst, the optimized catalytic system exhibits the best conversion of epoxide in presence of TBAI under the reaction temperature and time, respectively, 90°C and 6 hr, respectively. The ring opening polymerization of ε‐caprolactone is also appraised subjecting the Al derivatives, 1–3, as catalysts in presence of benzyl alcohol and all the conversions of ε‐caprolactone reach over 95% at the reaction condition of 100°C and 1 hr. [ABSTRACT FROM AUTHOR]

Styrene oxide isomerase (SOI) catalyzes the Meinwald rearrangement of aryl epoxides to carbonyl compounds via a 1,2‐trans‐shift in a stereospecific manner. A number of cascade biotransformations with SOI‐catalyzed epoxide isomerization as a key step have been developed to convert readily available substrates into valuable chiral chemicals. Cascade conversion of terminal or internal alkenes into chiral acids, alcohols or amines was achieved, which involved SOI‐catalyzed enantio‐retentive isomerization of terminal epoxides via 1,2‐H shift, or internal epoxides via 1,2‐methyl shift. SOI‐involved cascades were also developed to convert racemic epoxides into chiral acids or amines via dynamic kinetic resolution. Additionally, combining SOI‐catalyzed isomerization with enantioselective C−C bond forming enzymes enabled the synthesis of chiral amino acids or amino alcohols from racemic epoxides. Finally, integration of SOI‐involved cascades with biosynthesis pathways allowed for the direct utilization of renewable substrates for the sustainable synthesis of high‐value natural chemicals such as alcohols, acids, and esters. [ABSTRACT FROM AUTHOR]

Novel tridentate N2O‐type ligands L1–L4 (((((X‐benzyl)pyridine‐2‐yl)methylamino)methyl)phenol); L1 for X=4‐CH3, L2 for X=H, L3 for X=2‐F, L4 for X=4‐CF3) and their dinuclear copper(II) complexes C1–C4 (C1 for [(L1)2Cu2(NO3)2], C2 for [(L2)2Cu2(NO3)2], C3 for [(L3)2Cu2(NO3)2] and C4 for [(L4)2Cu2(NO3)2]) was synthesized and verified by 1H NMR, IR, and ESI‐Mass. The structural forms of the copper complexes were determined by X‐ray crystallography. The dinuclear copper complexes C1–C4 showed efficient ring‐opening properties of epoxides with methanol under mild conditions. In particular, the copper complex C1 having electron‐donating group in the ligand showed the most efficient reactivity in the ring opening of epoxides. The sole attack at the benzylic carbon of styrene oxide and the less steric preference in 1,2‐epoxyhexane demonstrated that the regiochemistry of the ring opening catalyzed by dinuclear copper complexes might be dependent on the electronic feature of epoxide. [ABSTRACT FROM AUTHOR]

Cr(III) centers have been incorporated into melamine‐terephthalaldehyde porous organic framework (MT‐POF) through N‐donor site coordination. Morphological studies by SEM give evidence of the transformation of spherulitic texture of non‐metalated MT‐POF to aggregated platelike structure in chromium metalated POF, MT‐Cr(III) POF (bulk). The flattening in the surface morphology of bulk MT‐Cr(III) POF might be a consequence of conformational change in POF caused by the template effect of the Cr(III) coordination. On sonication, bulk MT‐Cr(III) POF transformed into a distinguishable stacked nanosheet structure in MT‐Cr(III) POFN as revealed by FE‐SEM and TEM images. MT‐Cr(III) POFN could catalyse the carbon dioxide cycloaddition reaction to epoxides to yield cyclic carbonates in presence of tetrabutylammonium bromide (TBAB) co‐catalyst. It was found that bulkier epoxide substrates showed lesser conversions to their corresponding cyclic carbonates (styrene oxide, 41 %; allyl glycidyl ether, 70 %; butyl glycidyl ether, 63 % conv.), whereas smaller substrates showed much higher conversions (epichlorohydrin, 96 %; epibromohydrin, 95 % conv.) under the reaction conditions [MT‐Cr(III) POFN, 10 mg; TBAB, 2 mol%; 5 bar CO2; 60 °C] giving a clear evidence of the substrate discrimination. The reason for the lesser conversions of the bigger substrates can be attributed to the steric clash rendered by the POF network. [ABSTRACT FROM AUTHOR]

Unspecific peroxygenases (UPOs) are promising biocatalysts for oxyfunctionalisation reactions, owing to their simplicity of handling, stability and robustness. A limitation of using UPOs on a large scale is their deactivation in the presence of even rather modest concentrations of H2O2, requiring a constant and controlled supply of low amount of H2O2. Herein, we report an organometallic complex [Cp*Ir(pica)NO3] {pica=picolinamidate=κ2‐pyridine‐2‐carboxamide ion (−1)} 1 capable of efficiently regenerating FMNH2 from FMN (TOF=350 h−1, 298 K), driven by NaHCOO; FMNH2, in turn, spontaneously reacts with O2 leading to H2O2. After having studied the compatibility of 1 with the UPO from Agrocybe aegerita (rAaeUPO PaDa‐I) and individuated the best experimental conditions, we applied such a hybrid catalytic tandem in some hydroxylation, epoxidation and sulfoxidation reactions. Best performances were obtained by using a 1/rAaeUPO molar ratio of 50. TONs for the biocatalyst of up to 18933 were obtained for the transformation of ethylbenzene derivatives into (R)‐1‐phenylethanols (ee>99 %). 1/rAaeUPO was found to oxidise also cis‐methyl styrene (TON=13488), leading exclusively (1R,2S)‐cis‐methyl styrene oxide (ee>99 %), cyclohexane (TON=1634) and thioanisole (TON=1369). [ABSTRACT FROM AUTHOR]

Using photocatalytic oxidation to convert basic chemicals into high value compounds in environmentally benign reaction media is a current focus in catalytic research. The challenge lies in gaining controllability over product formation selectivity. We design covalent triazine frameworks as heterogeneous, metal‐free, and recyclable photocatalysts for visible‐light‐driven switchable selective oxidation of styrene in pure water. Selectivity in product formation was achieved by activation or deactivation of the specific photogenerated oxygen species. Using the same photocatalyst, by deactivation of photogenerated H2O2, benzaldehyde was obtained with over 99 % conversion and over 99 % selectivity as a single product. The highly challenging and sensitive epoxidation of styrene was carried out by creating peroxymonocarbonate as an initial epoxidation agent in the presence of bicarbonate, which led to formation of styrene oxide with a selectivity up to 76 % with near quantitative conversion. This study demonstrates a preliminary yet interesting example for simple control over switchable product formation selectivity for challenging oxidation reactions of organic compounds in pure water. [ABSTRACT FROM AUTHOR]

The nature of acidic sites in commercially available aluminosilicates, zeolite Na−Y, zeolite NH4+‐ZSM‐5, and as‐synthesized Al‐MCM‐41 have been investigated by employing them as catalysts for capturing CO2 by styrene oxide. The catalysts, in tandem with tetrabutylammonium bromide (TBAB), produce styrene carbonate, and the yield of the product is observed to be governed by the acidity of the catalysts and hence, the Si/Al ratio. All these aluminosilicate frameworks have been characterized by IR, BET, TGA, and XRD. XPS, NH3‐TPD, and 29Si solid‐state NMR studies have been carried out to analyze the Si/Al ratio and the acidity of these catalysts. According to TPD studies, the number of weak acidic sites of these materials follow an order as NH4+‐ZSM‐5 < Al‐MCM‐41 < zeolite Na−Y, which is just in accordance with their Si/Al ratios and the yield of the cyclic carbonates obtained, i. e. 55.3 %, 68 %, and 75.4 % respectively. The TPD data and the yield of the product carried out with calcined zeolite Na−Y indicate that not only the weak acidic sites but also the role of strong acidic sites might appear crucial in the cycloaddition reaction. [ABSTRACT FROM AUTHOR]

New types of one‐pot multi‐step enzymatic cascade transformation involving dynamic kinetic resolution to convert racemic substrates to chiral products in high ee and yield were developed. Unique cascade reactions of easily accessible racemic trans‐β‐methyl or α‐methyl epoxides to produce (S)‐2‐arylpropionic acids, (R)‐ and (S)‐2‐arylpropyl amines were demonstrated via styrene oxide isomerase (SOI)‐catalyzed Meinwald epoxide rearrangement to generate 2‐arylpropanal in situ, which was followed by spontaneous racemization, and alcohol dehydrogenase (ADH)‐catalyzed (S)‐enantioselective oxidation or transaminase (TA)‐catalyzed (R)‐ or (S)‐enantioselective amination, respectively. Cascade reactions performed with isolated enzymes or whole‐cell biocatalysts produced pharmaceutically relevant (S)‐2‐arylpropionic acids, (R)‐ and (S)‐2‐arylpropyl amines with high enantioselectivity and yield. The cascades starting with in situ aldehyde generation from epoxides effectively minimized side reactions related to aldehyde instability and displayed a wide substrate scope. [ABSTRACT FROM AUTHOR]

A series of ester‐ether copolymers were obtained via the reaction between α,ω‐dihydroxyl poly(ϵ‐caprolactone) (PCL) and ethylene oxide (EO) or monosubstituted epoxides catalyzed by strong phosphazene bases. The two types of monomeric units were distributed in highly random manners due to the concurrence of epoxide ring‐opening and fast transesterification reactions. The substituent of epoxide showed an interesting bidirectional effect on the enzymatic degradability of the copolymer. Compared with PCL, copolymers derived from EO exhibited enhanced hydrophilicity and decreased crystallinity which then resulted in higher degradability. For the copolymers derived from propylene oxide and 1,2‐butylene oxide, the hydrophobic alkyl pendant groups also allowed lower crystallinity of the copolymers thus higher degradation rates. However, further enlarging the pendant groups by using styrene oxide or 2‐ethylhexyl glycidyl ether caused a decrease in the degradation rate, which might be ascribed to the higher bulkiness hindering the contact of ester groups with lipase. [ABSTRACT FROM AUTHOR]

In this work, without template and additives, sheet‐like mesoporous Cu3(PO4)2 ⋅ 3H2O was successfully used to create by a simple solvothermal method. XRD, FT‐IR, BET and SEM methods were used to characterize the structure and properties of the samples that were produced. The results revealed that the stacked mesoporous structure of the target sheet‐like product was well‐formed, and the pore diameter was centered at 3.17 nm. In addition, the sheet‐like mesoporous Cu3(PO4)2 ⋅ 3H2O shows excellent ability to improve the yield of styrene oxide by the research of solvents, catalyst dosage, molar ratio of styrene/TBHP, the reaction temperature and the reaction time in the reaction system. Thus, when the solvent was acetonitrile, the catalyst dosage was 10 mg, the molar ratio of styrene/TBHP was 1 : 4, the reaction temperature was 80 °C, and the reaction time was 8 h, the yield of styrene was 74.7 % and the conversion of styrene was 96.7 %, demonstrating that styrene oxide and benzaldehyde were the major products of the process. The cyclic stability of the catalyst was further assessed, and implied that the catalytic activity, selectivity, and the catalyst's properties fails to change significantly after five cycles, which further indicates the superior stability of the catalyst. [ABSTRACT FROM AUTHOR]

Biocatalytic cascades are uniquely powerful for the efficient, asymmetric synthesis of bioactive compounds. However, high substrate specificity can hinder the scope of biocatalytic cascades because the constituent enzymes may have non‐complementary activity. In this study, we implemented a substrate multiplexed screening (SUMS) based directed evolution approach to improve the substrate scope overlap between a transaldolase (ObiH) and a decarboxylase for the production of chiral 1,2‐amino alcohols. To generate a promiscuous cascade, we engineered a tryptophan decarboxylase to act efficiently on β‐OH amino acids while avoiding activity on l‐threonine, which is needed for ObiH activity. We leveraged this exquisite selectivity with matched substrate scope to produce a variety of enantiopure 1,2‐amino alcohols in a one‐pot cascade from aldehydes or styrene oxides. This demonstration shows how SUMS can be used to guide the development of promiscuous, C−C bond forming cascades. [ABSTRACT FROM AUTHOR]

A series of ZnBr2 impregnated on rice husk ash silica catalysts were synthesised via the wet impregnation method for the CO2 cycloaddition to styrene oxide reaction. The X‐ray diffraction (XRD) analysis indicates that the impregnation resulted in the deterioration of the silica's pore channels. Catalyst with 0.5 w/w% of Zn (0.5 wt %ZnBr2‐SiO2) was highly active in the CO2 cycloaddition to styrene oxide. The conversion of styrene oxide (StO) was 89.1 %, with the styrene carbonate (SC) selectivity of 92.1 % under the optimum conditions (130 °C, 60 bar, 3 h and solventless). Additionally, the universality of 0.5 wt %ZnBr2‐SiO2 was also studied with other epoxides, and it shows good to excellent activity. The catalytic performance of the 0.5 wt %ZnBr2‐SiO2 remains constant after being reused three consecutive times. The activation energy of the reaction was determined to be 89.06 kJ/mol. [ABSTRACT FROM AUTHOR]

Highly selective and direct electroreductive ring‐opening carboxylation of epoxides with CO2 in an undivided cell is reported. This reaction shows broad substrate scopes within styrene oxides under mild conditions, providing practical and scalable access to important synthetic intermediate β‐hydroxy acids. Mechanistic studies show that CO2 functions not only as a carboxylative reagent in this reaction but also as a promoter to enable efficient and chemoselective transformation of epoxides under additive‐free electrochemical conditions. Cathodically generated α‐radical and α‐carbanion intermediates lead to the regioselective formation of α‐carboxylation products. [ABSTRACT FROM AUTHOR]

A regioselective hydroboration/hydrolysis of epoxides with pinacolborane catalyzed by NaOH/BEt3 was achieved. Glycidyl oxide, styrene oxide and adamantane epoxide underwent facile hydroboration/deprotection to provide secondary alcohols with exclusive selectivity in good to excellent yields. Moreover, the stereochemistry of epoxides could also be well retained, and the corresponding secondary alcohols were obtained with high optical activity under alkaline catalysis. Significantly, in this reaction, diverse functional groups can be compatible, including hydrogenation‐sensitive groups, such as carbon‐carbon double bonds and halogens. [ABSTRACT FROM AUTHOR]

In the search for a highly efficient heterogeneous catalyst for the epoxidation of styrene, it is still a challenge to develop a system that simultaneously possesses superior catalytic activity and selectivity under aerobic conditions. Herein, we report the use of perovskite LaSrCoFeO6 (LSCF) as a heterogeneous and visible‐light catalyst, and determine that LSCF acts as a highly efficient catalyst for the epoxidation of styrene under aerobic conditions. The formation of 1O2 species transformed from O2⋅− species were proposed as reactive oxygen species for the epoxidation of styrene over the LSCF catalyst, where the directional generation of O2⋅− species on the LSCF catalyst is the key step to yield highly selective epoxidation of styrene. The experimental results of styrene epoxidation show that when the molar ratio of styrene and LSCF catalyst is 150 : 1 and the reaction is under the conditions of visible light (440 nm) and 100 °C for 6 h, the conversion of styrene and selectivity of styrene oxide reached 99.9 % and 80.3 %, respectively. The reaction rate over LSCF catalyst is as high as 50 mmol ⋅ gcat−1 ⋅ h−1. In addition, the reaction kinetics of the epoxidation of styrene over LSCF catalyst was systematically studied. [ABSTRACT FROM AUTHOR]

In this work, four new mononuclear Cr(III) complexes (2–5) bearing bis‐thioether‐diphenolate, [OSSO]‐type ligands, were synthesized and characterized. These complexes in combination with bis(triphenylphosphine)iminium chloride (PPNCl) promoted the coupling of CO2 with epoxides. Depending on the type of substrate and the conditions, the reaction results in the selective formation of either polycarbonate or cyclic carbonate. For example, the reactions in the presence of complex 2 led to the exclusive formation of poly(cyclohexene carbonate, PCHC) from cyclohexene oxide (CHO) (TOF up to 39 h−1, at T=45–100 °C, time=24 h, pCO2=20 bar, epoxide/2 (mol/mol)=1000, and PPNCl/2=0.5–2.0 mol %). Under the same conditions and PPNCl/2=0.5–5.0 mol %, the reactions of CO2 with styrene oxide (SO), epichlorohydrin (ECH), 1,2 epoxydodecane (EDD), and allyl glycidyl ether (AGE) have shown selective conversion to the corresponding cyclic carbonates (TOF up to 41 h−1). [ABSTRACT FROM AUTHOR]

A mild, efficient, and metal‐free synthetic protocol for the synthesis of β‐amino alcohols is reported. The reaction proceeds at room temperature with only 0.5 mol % catalyst loading and affords β‐amino alcohol derivatives in excellent yield. This protocol is well‐tolerated by a wide range of styrene oxide and aniline derivatives. A notably efficacious gram‐scale synthesis is also reported with a high TON=842. Further, the Hammett correlation study was also performed to identify the rate‐determining step. [ABSTRACT FROM AUTHOR]

The Meinwald rearrangement is a synthetically useful reaction but often lacks regioselectivity and stereocontrol. A significant challenge in the Meinwald rearrangement of internal epoxides is the non‐regioselective migration of different substituents to give a mixture of products. Herein, an enzyme‐catalyzed regioselective and stereospecific 1,2‐methyl shift in the Meinwald rearrangement of internal epoxides is reported. Styrene oxide isomerase (SOI) catalyzed the unique isomerization of internal epoxides through 1,2‐methyl shift without 1,2‐hydride shift to give the corresponding aldehydes and a cyclic ketone as the sole product. SOI‐catalyzed isomerization showed high stereospecificity, fully retaining the stereoconfiguration. The synthetic utility of this enzymatic Meinwald rearrangement was demonstrated by its incorporation into three new types of enantioselective cascades, to convert trans‐β‐methyl styrenes into the corresponding R‐configured alcohols, acids, or amines in high ee and yield. [ABSTRACT FROM AUTHOR]

We undertake silver cyanide (AgCN) powder for its catalytic epoxidation of cyclohexene or styrene in CH3CN with variable substrate‐to‐solvent volume ratios using H2O2(aq) at 60 °C. The reaction mixtures can facilely separate into organic and aqueous layers. Cyclohexene oxide can be produced in the organic layer with 100 % selectivity from the substrate cyclohexene, while styrene oxide was identified with 80 % selectivity against benzaldehyde in styrene oxidation. After reactions, we can recycle the AgCN particles with comparable bulk property clarified via XRD, XPS, XAS, FT‐IR, and 13C‐SS NMR spectroscopy. Using H218O2 as the oxidant, both epoxide products and acetamide are highly enriched with 18O‐atom, indicating that the π bond‐activation is essential for forming the cyclohexene/styrene oxides in the organic and acetamide in the aqueous layers. The oxidation of cyclohexene/styrene catalyzed by AgCN powder through surface activation by H2O2(aq) and assisted by the non‐innocent CH3CN‐originated acetamide can achieve highly selective π‐bond activation with high reactivity. [ABSTRACT FROM AUTHOR]

A novel electrochemically assisted cycloaddition process is proposed, in which highly efficient coupling of CO2 with styrene oxide (SO) can be achieved to form styrene carbonate (SC) as a high‐value‐added product. A series of Cu catalysts with different morphologies and chemical states were fabricated on carbon paper (CP) by using in‐situ electrodeposition, and the sample with nano‐dendrimer structure was found to exhibit a relatively high activity of 74.8 % SC yield with 92.7 % SO conversion under gentle reaction conditions, thus showing its potential for practical applications. The relatively high electrochemically active surface area and charge transfer ability of dendrimer‐like Cu benefited the electrochemical reaction. In particular, the Cu2+ species that were formed in situ during the reaction played a vital role in enhancing the activity and selectivity of the proposed Cu/CP hybrid catalyst. Cu2+ atoms served as active sites that can not only electrochemically activate CO2 but also facilitate the ring opening of SO. Mechanistic analysis suggested that the reaction followed electrochemical and liquid‐phase heterogeneous paths, which provide a new green and sustainable route for efficient utilization of CO2 resources for fine chemical electrosynthesis. [ABSTRACT FROM AUTHOR]

Controllable deposition of nanosphere with zeolitic imidazolate frameworks (ZIFs) is an efficient method to achieve unique properties and create new types of multifunctional ZIF core–shell materials with enhanced properties. Core‐shell ZIF‐67@CeO2 nanosphere was designed with ZIF‐67 nanoparticles as seed for the deposition of CeO2 nanocrystals. The as‐prepared ZIF‐67@CeO2 nanosphere can catalyze CO2 cycloaddition reaction with significant activity. The synergistic acid‐base catalytic sites of ZIF‐67@CeO2 nanosphere were investigated through TPD analysis. These sites can effectively coordinate and activate the substrate molecules, thereby enhancing catalytic efficiency for CO2 cycloaddition reaction. The ZIF‐67@CeO2 nanosphere showed almost 100.00 % conversion of styrene oxide and 100.00 % selectivity of desired cyclic carbonate (120 °C, 7.5 bar, and 8 h). In addition, ZIF‐67@CeO2 showed a negligible decrease in the catalytic activity even after being reused for four cycles. [ABSTRACT FROM AUTHOR]

The metal‐templated hydrogen bond donors (HBD) are prospective catalytic systems for the activation of organic molecules in chemical reactions. Here we report the application of the chiral cationic Co(III) complexes based on commercially available (S,S)‐1,2‐diaminocyclohexane and (R,R)‐1,2‐diphenylethylendiamine and salicylaldehydes with an iodide counter‐anion as bifunctional one‐component hydrogen bond donor/nucleophilic catalysts for the conversion of carbon dioxide with epoxides into valuable cyclic carbonates under solvent‐ and co‐catalyst free conditions. We demonstrated that (R,R)‐1,2‐diphenylethylendiamine based complex Λ(R,R)‐2 is superior to (S,S)‐1,2‐diaminocyclohexane based Δ(S,S)‐1 a catalyzing the reaction at ambient conditions (RT and 1 bar CO2). The TON and TOF values of 850 and 35 h−1, respectively, were achieved at low catalyst loading (0.1 mol %) at 10 bars of CO2 and 100 °C. Furthermore, the Co(III) complexes catalyzed the reaction with diluted air/CO2 mixture (15 vol % of CO2) producing the desired styrene carbonate in up to 75% yield. A plausible catalytic cycle consistent with all experimental observations was proposed based on DFT calculations. The DFT calculations elucidated the difference in the ring opening step in cases of propylene oxide and styrene oxide. In addition, the kinetic resolution of terminal epoxides was observed with selectivity factor (s) of up to 1.6 in case of the complex Λ(R,R)‐2. [ABSTRACT FROM AUTHOR]

Supramolecular catalysis can provide distinct advantages for the catalytic conversion of CO2 into carbonates by cycloaddition to epoxides. For example, the absence of metals in the catalytic site, and the easy design for optimization. The incorporation of multiple functionalities in pseudopeptidic macrocycles with a pendant arm allows catalytic systems to be obtained where halide anions (nucleophilic activating agents for epoxides), hydrogen bond acceptor sites (activating agents for epoxides and stabilizing sites for anionic intermediates), and amine groups (Lewis basic sites for activating CO2) are in proximity. This allows a high activity in the cycloaddition of CO2 to styrene oxide under mild conditions (turnover number (TON) = 900, CO2 balloon, 100 °C, 5 h). The primary amino groups in the arm facilitate the immobilization of these macrocyclic structures in cross‐linked polymeric matrices containing ammonium halide fragments. Such multifunctional insoluble polymers afford excellent catalytic results with high TON and turnover frequency values and remarkable productivities (>10 gprod gresin−1 h−1). This activity is maintained for a variety of epoxides and is retained after several catalytic runs. Their performance is significantly higher than those reported for most heterogenous supramolecular catalytic systems for CO2 transformation into carbonates. [ABSTRACT FROM AUTHOR]

TAMOF‐1, a homochiral metal‐organic framework (MOF) constructed from an amino acid derivative and Cu(II), was investigated as a heterogeneous catalyst in kinetic resolutions involving the ring opening of styrene oxide with a set of anilines. The branched products generated from the ring opening of styrene oxide with anilines and the unreacted epoxide were obtained with moderately high enantiomeric excesses. The linear product arising from the attack on the non‐benzylic position of styrene oxide underwent a second kinetic resolution by reacting with the epoxide, resulting in an amplification of its final enantiomeric excess and a concomitant formation of an array of isomeric aminodiols. Computational studies confirmed the experimental results, providing a deep understanding of the whole process involving the two successive kinetic resolutions. Furthermore, TAMOF‐1 activity was conserved after several catalytic cycles. The ring opening of a meso‐epoxide with aniline catalyzed by TAMOF‐1 was also studied and moderate enantioselectivities were obtained. [ABSTRACT FROM AUTHOR]

A series of MOFs with a 6‐connected spn topology were synthesized (MOF‐808‐(Zr, Hf), PCN‐777‐(Zr, Hf), MOF‐818‐(Zr, Hf)). Through the in situ DRIFTS of NH3 adsorption‐desorption, we found that the activated catalyst mainly contains Lewis acid sites. The effects of different organic ligands on the Lewis acid of the Zr6 cluster were analyzed by XPS and NH3‐TPD, and the relative Lewis acidity of the same metal was obtained: PCN‐777>MOF‐808>MOF‐818. In the Py‐FTIR results, we confirmed that MOF‐818 has a higher acid site density. In the activity test, MOFs with mesoporous structure showed better catalytic activity under normal temperature and pressure. Among them, MOF‐818 can still maintain a high degree of crystallinity after catalysis. Finally, we use density functional theory to propose the mechanism of the cycloaddition reaction of carbon dioxide and styrene oxide. The results show that the metal is coordinated with styrene oxide and halogens attack the β carbon of the epoxide. [ABSTRACT FROM AUTHOR]

Keywords: biomass; carbonization; CO2 cycloaddition; ionic liquids; paper mill sludgeUpcycling Waste BiomassIn article number 2300655, Marcileia Zanatta, Marta C. Corvo, and co‐workers show that, by transforming paper industry waste into porous carbonaceous materials, these materials serve as effective supports in the ionic liquid‐catalyzed cycloaddition of CO2 to styrene oxide, achieving high conversion rates and selectivity..By Mónica Stanton Ribeiro; Maria M. R. A. Lima; Márcia Vilarigues; Marcileia Zanatta and Marta C. CorvoReported by Author; Author; Author; Author; Author [Extracted from the article]

Sustainable initiatives using various biologically active plant materials have been receiving huge amount of attention in the immediate past. Herein, we present the plant mediated synthetic methodology for preparing zinc oxide (ZnO) nanoparticles (NPs) via a greener protocol using water chestnut peel (WCP), an agricultural bio‐waste whose versatility is well known both behaving as a stabilizing and reducing agent. This method of synthesis of ZnO NPs ensures a cost competitive, non‐toxic, economically viable and environmentally benign pathway while using WCP as efficient scaffolds. The crystalline nature and morphology of as synthesized NPs were confirmed using Powder X‐ray Diffraction (PXRD) and Scanning Electron Microscopy (SEM). Biogenically synthesized NPs have average crystalline size 20.49 nm and irregular spikes morphology. Furthermore, the biogenically synthesized ZnO NPs were utilized for catalysing the ring opening reaction of styrene oxide from aniline and aniline derivatives enabling the reaction reach up to 99 % yields. Motivated by the excellent conversion of ring opening reaction the biogenically synthesized catalyst has also been explored to earmark their versatility and efficiency for facilitating numerous organic transformations which simultaneously emphasise their role in safeguarding the environment. [ABSTRACT FROM AUTHOR]

Tuning graphitic surface with nitrogen functionalities renders potential carbocatalysts for a wide range of reactions. Herein, g‐C3N4/graphite composite material (g‐C3N4@G) is reported for oxidation of styrene to styrene oxide. The detailed physiochemical properties of g‐C3N4@G are investigated by X‐ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), X‐ray diffraction (XRD) and Fourier transmission infrared spectroscopy (FTIR) analysis. The TEM and SEM micrographs indicate the formation of g‐C3N4 sheets and N1s XPS results confirm the formation of g‐C3N4 on the graphitic surface. The role of specific catalytic sites is experimentally studied by the use of model catalysts those mimic the functional groups on the surface of g‐C3N4@G. It is suggested that the catalytic sites on the surface showcase a synergeistic effect, with sp2 hybridized N site being most selective for styrene oxide. [ABSTRACT FROM AUTHOR]

An iron (II) complex with oxazoline and pyrrole functional groups was prepared and used to catalyze the epoxidation of alkenes by m‐chloroperoxybenzoic acid. The iron (II) complex exhibited good catalytic activity for the epoxidation of aromatic terminal alkenes and cyclic alkene in acetonitrile. The 99.7 % conversion of styrene with 91.2 % selectivity of styrene oxide was achieved after reaction 30 minutes at 25 °C. The auxiliary ligands, solvents and oxidants are sensitive to the epoxidation reaction. A possible catalytic mechanism for epoxidation of alkene was proposed. [ABSTRACT FROM AUTHOR]

Given the capture and utilization of carbon dioxide (CO2) emission, the CO2 separation and catalysis fixation of CO2 and epoxides have been of intense interest. In this respect, a microporous copper-based metal-organic framework (MOF) Cu2(ABTC) (ABTC=3,3’,5,5’-azobenzenetetra-carboxylic acid) was synthesized. The Cu–MOF endowed with open Cu sites, accessible pore cages and hexagonal channel (9.6 & 11 Å) exhibits permanent porosity (BET surface area of 2200 m²g -1 ), good low-pressure CO2 uptake (93 cm3g 1, at 298 K), and moderate CO2 selectivity over N2 and CH4. In light of catalysis fixation of CO2 and epoxides, Cu2(ABTC) exhibited outstanding performance with high conversion of styrene oxide (96%), and yield towards the formation of styrene carbonate (90%) under mild conditions (1 atm of CO2, 60°C, 8 h). Notably, the catalytic activity of Cu2(ABTC) outperformed that of other Cu-MOFs, and the recovered Cu2(ABTC) can be reused up to six times without considerable reduction in catalytic activity. [ABSTRACT FROM AUTHOR]

NiII and MnIII Schiff base complexes (Salophen‐Ni and Salophen‐MnCl) bearing a pending carboxylic group were prepared and characterized. Both complexes were grafted onto a mesoporous amino‐functionalized SBA‐15 silica, by formation of an amide function between the propylamine groups of the support and the carboxylic acid functions of the salophen ligand (corresponding respective to 1.30 wt.% of Ni and 1.06 wt.% of Mn). The co‐catalytic behaviour of the free and grafted complexes was then evaluated in the CO2 cycloaddition reaction onto styrene oxide, using tetra‐butylammonium bromide (n−Bu4NBr) as the main catalyst. In homogeneous conditions, the MnIII Schiff base complex and the NiII one, to a lesser extent, behave as efficient co‐catalysts for this reaction (styrene conversion of 100 % and 65 % respectively after 3 h at 120 °C, under 15 bars of CO2). Upon immobilization at the surface of the amino‐functionalized SBA‐15, we showed that the co‐catalytic activity of the less efficient one, i. e. Ni2+ salophen complex, could be enhanced (reaching a full conversion after 7 h), hence highlighting a potential synergistic effect between the unused amine functions of the support and the Ni2+ salophen co‐catalyst. Both salophen complexes were successfully re‐used in homogeneous conditions or after their immobilization without any appreciable loss of activity. This work is only a first step towards a completely heterogeneous catalytic system, in which the tetraalkylammonium halide catalyst and the metal‐salophen co‐catalyst will both be covalently anchored on the same support. [ABSTRACT FROM AUTHOR]

CO2 insertion reactions on terminal epoxides (styrene oxide, 1,2‐epoxyhexane and butyl glycidyl ether) were performed in a binary homogeneous mixture comprising NaBr as the nucleophilic catalyst and diethylene glycol (DEG) as both solvent and catalyst activator (cation coordinating agent). The reaction protocol was initially studied under batch conditions either in autoclaves and glass reactors: quantitative formation of the cyclic organic carbonate products (COCs) were achieved at T=100 °C and p0(CO2)=1–40 bar. The process was then transferred to continuous‐flow (CF) mode. The effects of the reaction parameters (T, p(CO2), catalyst loading, and flow rates) were studied using microfluidic reactors of capacities variable from 7.85 ⋅ 10−2 to 0.157 cm3. Albeit the CF reaction took place at T=220 °C and 120 bar, CF improved the productivity and allowed catalyst recycle through a semi‐continuous extraction procedure. For the model case of 1,2‐epoxyhexane, the (non‐optimized) rate of formation of the corresponding carbonate, 4‐butyl‐1,3‐dioxolan‐2‐one, was increased up to 27.6 mmol h−1 equiv.−1, a value 2.5 higher than in the batch mode. Moreover, the NaBr/DEG mixture was reusable without loss of performance for at least 4 subsequent CF‐tests. [ABSTRACT FROM AUTHOR]