Conversion Of Epoxides Research Articles

Cerium Pyrazolates Grafted onto Mesoporous Silica SBA-15: Reversible CO2 Uptake and Catalytic Cycloaddition of Epoxides and Carbon Dioxide.

The activation and catalytic conversion of CO2 is a current topic relating to molecular chemistry and materials science alike. As a transdisciplinary field of research, surface organometallic chemistry (SOMC) might be applicable to perform synergistically, thus striking a new path in sustainable chemistry. Both ceric and cerous rare-earth-metal pyrazolates, which were recently shown to reversibly insert CO2 and to promote the catalytic cycloaddition of epoxides and carbon dioxide, were grafted onto large-pore mesoporous silica SBA-15500, thermally pretreated at 500 °C. The obtained hybrid materials [Ce(Me2pz)4]2@SBA-15500, Ce(Me2pz)4(thf)@SBA-15500, Ce4(Me2pz)12@SBA-15500, and [Ce(Me2pz)3(thf)]2@SBA-15500 (Me2pz = 3,5-dimethylpyrazolato) were characterized by DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy), solid-state 1H/13C NMR spectroscopy, elemental analysis, ICP/OES, and N2 physisorption. The lanthanum(III)-based material [La(Me2pz)3(thf)]2@SBA-15500 was synthesized for better assessment of the cerous materials being highly sensitive to oxidation. To mimic ceric surface species, Ce[OSi(OtBu)3]3Cl was treated with 1 equiv of K(Me2pz), generating the mixed pyrazolyl/siloxy complex KCe[OSi(OtBu)3]4(Me2pz) featuring a cerium(IV)-bonded terminal pyrazolato ligand. All hybrid materials show efficient and reversible carbon dioxide uptake of maximum 20 wt % in the solid state. When combined with tetra-n-butylammonium bromide (TBAB), the hybrid materials catalyze the cycloaddition of CO2 and epoxides, displaying good conversion of various epoxides and reusability.

Towards Thermally Reversible Networks Based on Furan-Functionalization of Jatropha Oil.

A novel biobased monomer for the preparation of thermally reversible networks based on the Diels-Alder reaction was synthesized from jatropha oil. The oil was epoxidized and subsequently reacted with furfurylamine to attach furan groups via an epoxide ring opening reaction. However, furfurylamine also reacted with the ester groups of the triglycerides via aminolysis, thus resulting in short-chain molecules that ultimately yielded brittle thermally reversible polymers upon cross-linking via a Diels-Alder reaction. A full-factorial experimental design was used in finding the optimum conditions to minimize ester aminolysis and to maximize the epoxide ring opening reaction as well as the number of furans attached to the modified oil. The optimum conditions were determined experimentally and were found to be 80 °C, 24 h, 1:1 molar ratio, with 50 mol % of LiBr with respect to the modified oil, resulting in 35% of ester conversion, 99% of epoxide conversion, and an average of 1.32 furans/triglyceride. Ultimately, further optimization by a statistical approach led to an average of 2.19 furans per triglyceride, which eventually yielded a flexible network upon cross-linking via a Diels-Alder reaction instead of the brittle one obtained when the furan-functionalization reaction was not optimized.

Hydroxy-containing ionic liquids as catalysts in the synthesis of organic carbonates from epoxides and CO2

Hydroxy-containing ionic liquids such as triethyl(3-hydroxypropyl)ammonium, 1-(3-hydroxypropyl)-3-methylimidazolium, 3-(2-hydroxyethyl)-1-methylimidazolium, and 1-(3-hydroxypropyl)pyridinium chlorides were used as catalysts for the addition of carbon dioxide to epoxides, which gives cyclic carbonates. The effect of CO2 pressure and reaction temperature on the conversion of epoxides, as well as a promoting effect of inorganic substrates were studied.

Detailed chemomechanistic sensitivity study on the alkoxylation of fatty amines

AbstractThe mechanism of the autocatalytic alkoxylation of fatty amines was elucidated using a combined experimental and theoretical approach. The kinetic parameters of the elementary reaction steps are fitted to the experimental data gained in semibatch for propylene and butylene oxides with dodecylamine. A quality‐of‐fit sensitivity study was conducted to assess the robustness and accuracy of the model. Herein, we identified the kinetic parameters that are either crucial for a good fit or rate controlling in terms of the overall kinetics. It was found that the critical steps are the activation of the epoxide ring by a hydroxyl group present on either the intermediate or final product, highlighting the autocatalytic nature of the reaction. Furthermore, we introduced a so‐called degree of conversion control to characterize the importance of each elementary reaction step toward the epoxide conversion. The degree of conversion control showed that the uncatalyzed route toward the secondary amine is only influential at low conversion. At higher conversion the route via the catalytic intermediate dominates. Alternative mechanisms were investigated as well but did not significantly improve the quality of fitting and were thus discarded.

Critical Roles of Doping Cl on Cu2O Nanocrystals for Direct Epoxidation of Propylene by Molecular Oxygen.

Direct epoxidation of propylene by molecular oxygen alone is one of the "dream reactions" in heterogeneous catalysis. Despite much effort, the yield of propylene epoxide is still too low to be commercially attractive due to the trade-off between conversion and selectivity. Here, we demonstrate that doping Cl into the lattice of Cu2O nanocrystals by the intergrowth method not only can enhance the catalytic selectivity and conversion of direct propylene epoxidation but also can solve the long-existing Cl loss problem. In particular, Cl-doped rhombic dodecahedral Cu2O with (110) exposing facets exhibited 63% PO selectivity with a 12.0 h-1 turnover frequency at 200 °C, outperforming any other coinage metal-based catalysts under mild conditions. Comprehensive characterization and theoretical calculations revealed that the Cl-decorated Cu(I) facilitated formation of electrophilic oxygen species, thus boosting the production of propylene oxide. This work provides a general strategy to develop catalysts and explore the promoter effect by creating uniform isolated anion doping to activate a nearby metal center by virtue of well-defined nanocrystals.

A Porous CoII-MOF for CO2 Cycloaddition and the Protective Effect against Staphylococcus aureus Systemic Infection in the Department of Ultrasound

A new metal-organic framework (MOF) based on CoII ions as nodes, [Co2(H2O)3(cada)](DMF)4, which has coordinated water molecules at the occupied CoII sites along with a suitable pore environment, was constructed by reaction of 5,5′-(9H-carbazole-2,7-diyl)diisophthalic acid (H4cada) and Co(NO3)2·6H2O in a water and DMF mixed solvent. The resulting activated MOF 1ais able to uptake considerable amounts of CO2 at room temperature, and be further used for the efficient conversion of epoxides along with CO2 into cyclic carbonates under mild conditions without a co-catalyst. To control intra-hospital cross-infection in the Department of Ultrasound, the anti-bacterial activity of the compound was assessed in a systemic Staphylococcus aureus infection mouse model. The survival rate of systemic Staphylococcus aureus infected mice after compound treatment was determined to evaluate protective effect of the compound invivo. The number of colony-forming units (CFUs) in the organs of infected mice was also counted for further verification.

36-LB: Linoleic Acid Derived Oxylipins, Memory, and Microvascular Retinal Complications in Patients with Type 2 Diabetes Mellitus

Introduction: Memory decline is accelerated in type 2 diabetes mellitus (T2DM), and it is thought that microvascular disease may be a contributor. Oxylipins, bioactive lipid species derived from polyunsaturated free fatty acids such as linoleic acid, can act on small vessels. Cytochrome p450 derived epoxides may be immunologically active, whereas their hydrolysis into diols by soluble epoxide hydrolase (sEH) may render them inactive or cytotoxic. We examine linoleic acid epoxide and diol concentrations in peripheral blood and their associations with memory performance and retinal microvascular disease in patients with T2DM or prediabetes. Methods: Patients with T2DM or prediabetes were recruited from 3 sites. Memory was assessed via California Verbal Learning Test 2nd Edition (CVLT-II). Patient history of retinopathy was recorded. Serum oxylipin concentrations were measured via ultra-high-performance liquid chromatography tandem mass-spectrometry. Results: In people with T2DM or prediabetes (n=76, 55% women, 63±9 years old, HbA1C=7.4±1.2% mmol/mol, duration of diabetes 8±10 years), 9.2% had retinopathy, and the mean CVLT-II was -0.07±1.01 Z-score units (indicating generally average performance). The linoleic acid derived epoxide 12(13)-epoxyoctadecenoic acid concentration was negatively correlated with CVLT-II performance (β=-0.298, p=0.003), whereas the diol derived from that species (12,13-dihydroxyoctadecenoic acid) was elevated in people with retinopathy (9.1±4.1 nM vs. 6.5±11.5 nM, U=72.0, p=0.008). Discussion: Oxylipins generated by cytochrome p450 and sEH should be explored as potential biomarkers for cognitive complications and microvascular disease in T2DM. The observed relationships might suggest the presence of a cytochrome p450-mediated response that may generate differential response and lack benefit in T2DM, possibly due to sEH-mediated conversion of epoxides into diols, warranting further study. Disclosure S.K. Wong: None. M.M. Nguyen: None. C. Major-Orfao: None. K.L. Lanctôt: None. N. Herrmann: None. P. Oh: None. B.R. Shah: None. J. Gilbert: Speaker’s Bureau; Self; Abbott, Amgen, Ascensia Diabetes Care. Other Relationship; Self; AstraZeneca, Boehringer Ingelheim (Canada) Ltd., Dexcom, Inc., Eli Lilly and Company, Janssen Pharmaceuticals, Inc., Merck & Co., Inc., Novo Nordisk Inc., Sanofi. A. Assal: None. I. Halperin: Advisory Panel; Self; Tandem Diabetes Care. Speaker’s Bureau; Self; Abbott, Boehringer Ingelheim (Canada) Ltd., Dexcom, Inc., Novo Nordisk Inc., Sanofi. P. Yang: None. T. Pedersen: None. A. Taha: None. W. Swardfager: None. Funding Canadian Institutes of Health Research (410010992)

Allyl functionalized UiO-66 metal-organic framework as a catalyst for the synthesis of cyclic carbonates by CO2 cycloaddition

The conversion of epoxides to cyclic carbonates is one of the most common CO2 fixation reactions. Metal-organic frameworks (MOFs), due to their porosity, easily tunable properties and Lewis acidic sites, are extensively used in heterogeneous catalysis. In this paper, we report the derivatization of the metal-organic framework (MOF) UiO-66 (University of Oslo) with allyloxy groups to give UiO-66-BAT (BAT=bisallyloxyterephthalate). The catalyst was characterized by PXRD, BET, IR, SEM, digestion NMR and CO2 adsorption. UiO-66-BAT had a good CO2 uptake of 84cc/g at 273K and a Qst value of 27.5kJmol−1. Due to the affinity of the allyloxy group toward CO2 and the proximity of the zirconium Lewis acid sites, we applied UiO-66-BAT as a catalyst for the conversion of epoxides to cyclic carbonates by using CO2. We showed that UiO-66-BAT converts propylene oxide (PO) to its corresponding cyclic carbonates at 50°C, a 5bar pressure, and a 6 h reaction time with a 95% yield. UiO-66-BAT also gave a good yield in the conversion of numerous aliphatic and aromatic epoxides. The catalysts exhibited a good recyclability for up to 9 cycles.

Identification and catalytic properties of new epoxide hydrolases from the genomic data of soil bacteria

Epoxide hydrolases (EHs) catalyse the conversion of epoxides into vicinal diols. These enzymes have extensive value in biocatalysis as they can generate enantiopure epoxides and diols which are important and versatile synthetic intermediates for the fine chemical and pharmaceutical industries. Despite these benefits, they have seen limited use in the bioindustry and novel EHs continue to be reported in the literature.We identified twenty-nine putative EHs within the genomes of soil bacteria. Eight of these EHs were explored in terms of their activity. Two limonene epoxide hydrolases (LEHs) and one ⍺/β EH were active on a model compound styrene oxide and its ring-substituted derivatives, with low to good percentage conversions of 18–86%. Further exploration of the substrate scope with enantiopure (R)-styrene oxide and (S)-styrene oxide, showed different epoxide ring opening regioselectivities. Two enzymes, expressed from plasmids pQR1984 and pQR1990 de-symmetrised the meso-epoxide cyclohexene oxide, forming the (R,R)-diol with high enantioselectivity. Two LEHs, from plasmids pQR1980 and pQR1982 catalysed the hydrolysis of (+) and (−) limonene oxide, with diastereomeric preference for the (1S,2S,4R)- and (1R,2R,4S)-diol products, respectively. The enzyme from plasmid pQR1982 had a good substrate scope for a LEH, being active towards styrene oxide, its analogues, cyclohexene oxide and 1,2-epoxyhexane in addition to (±)-limonene oxide.The enzymes from plasmids pQR1982 and pQR1984 had good substrate scopes and their enzymatic properties were characterised with respect to styrene oxide. They had comparable temperature optima and pQR1984 had 70% activity in the presence of 40% of the green solvent MeOH, a useful property for bio-industrial applications. Overall, this study has provided novel EHs with potential value in industrial biocatalysis.

Synthesis of cyclic carbonates by ruthenium(VI) bis-imido porphyrin/TBACl-catalyzed reaction of epoxide with CO2

The catalytic activity of the ruthenium(VI) bis-imido porphyrin complex/TBACl binary system in promoting the CO[Formula: see text] cycloaddition to epoxides forming cyclic carbonates is here reported. The system was very efficient in catalyzing the conversion of differently substituted epoxides under mild experimental conditions (100 [Formula: see text]C and 0.6 MPa of CO[Formula: see text]. Even if the sole TBACl resulted active under the optimized experimental conditions, the addition of ruthenium species was fundamental to maximizing the reaction productivity both in terms of epoxide conversions and cyclic carbonate selectivities. A preliminary mechanistic study indicated a positive role of ruthenium imido nitrogen atom in activating carbon dioxide.

Catalytic Isomerization of α-Pinene Epoxide Over a Natural Zeolite

Isomerization of α-pinene epoxide was carried out over a Colombian natural zeolite as potential geocatalyst with heulandite, chabazite and clipnotilolite as main crystallographic phases; the heulandite was identified as the active phase. Over synthetic zeolites, isomerization of α-pinene epoxide depended on Si/Al ratio, unit cell and the kind of structure. The best solvent was toluene and not isomerization activity was observed in presence of solvents with carboxyl groups. Complete α-pinene epoxide conversion and 45% selectivity to campholenic aldehyde were obtained at 70 °C, with fencholenic aldehyde, carveol, and p-cymene as main by-products. Decrease of activity of natural zeolite was associated with loss of acid sites. A reaction mechanism based on experimental and computational data was proposed including adsorption of α-pinene epoxide on Fe or Al sites of the natural zeolite; a reaction rate constant of 4.02 × 10–4 mol g−1 min−1 was estimated from a pseudo homogeneous kinetic model.

Triazine-based Organic Polymer-catalysed Conversion of Epoxide to Cyclic Carbonate under Ambient CO2 Pressure.

In this work we have achieved epoxide to cyclic carbonate conversion using a metal-free polymeric catalyst under ambient CO2 pressure (1.02 atm) using a balloon setup. The triazine containing polymer (CYA-ANIS) was prepared from cyanuric chloride (CYA-Cl) and o-dianisidine (ANIS) in anhydrous DMF as solvent by refluxing under the N2 gas environment. The presence of triazine and amine functional groups in the polymer results in the adsorption of CO2 up to 7 cc/g at 273 K. This inspired us to utilize the polymer for the conversion of a series of functionalised epoxides into their corresponding cyclic carbonates in the presence of tetrabutyl ammonium iodide (TBAI) as co-catalyst. The product has wide range of applications like solvent in lithium ion battery, precursor for polycarbonate, etc. The catalyst was efficient for the conversion of different mono and di-epoxides into their corresponding cyclic carbonates under atmospheric pressure in the presence of TBAI as co-catalyst. The study indicates that epoxide attached with electron withdrawing groups (like, CH2 Cl, glycidyl ether, etc.) displayed better conversion compared to simple alkane chain attached epoxides. This is mainly due to the stabilization of electron rich intermediates produced during the reaction (e. g. epoxide ring opening or CO2 incorporation into the halo-alkoxide anion). This catalyst mixture was capable to maintain its reactivity up to five cycles without losing its activity. Post catalytic characterization clearly supports the heterogeneous and recyclable nature of the catalyst.

Squaramide–Quaternary Ammonium Salt as an Effective Binary Organocatalytic System for Oxazolidinone Synthesis from Isocyanates and Epoxides

Squaramide–quaternary ammonium salt is illustrated as a simple, tunable, and competent metal‐free binary catalytic platform for the atom‐economic conversion of epoxides and isocyanates into oxazolidinones. Although, various metal catalysts have been employed for the title reaction, application of organocatalysis is scarce. At first, a rational survey of catalytic activity of several air‐stable and architecturally distinct squaramides was undertaken. Thereafter, the impact on catalytic capability of different parameters, such as temperature, catalyst loading, and nature of nucleophiles, was examined. This binary organocatalytic system for the oxazolidinone synthesis, composed of a squaramide entity along with a suitable halide anion, was applied to the challenging conversion of a plethora of alkyl‐ and aryl‐substituted epoxides– including disubstituted and enantioenriched ones– and isocyanates into the corresponding oxazolidinones in high‐to‐excellent yields. The time‐dependent formation of oxazolidinone from epoxide and isocyanate was monitored by FTIR‐ATR and 1H NMR spectroscopy and the scalability of this process was also described. In light of 1H NMR experiment, a hydrogen‐bonding/anion‐binding mechanism was proposed wherein the nucleophilic ring‐opening operation, and oxo‐ and carbamate‐anions stabilization occur cooperatively towards isocyanate fixation.

Assessment of the Effect of Sorafenib on Omega-6 and Omega-3 Epoxyeicosanoid Formation in Patients with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of cancer death. The multikinase inhibitor sorafenib is widely used for systemic therapy in advanced HCC. Sorafenib might affect epoxyeicosanoids, as it is also a potent inhibitor of the soluble epoxide hydrolase (sEH), which catalyzes the conversion of epoxides derived from long-chain polyunsaturated fatty acids (PUFAs), such as arachidonic acid (AA) and omega-3 docosahexaenoic acid (DHA), into their corresponding diols. Experimental studies with AA-derived epoxyeicosatrienoic acids (EETs) showed that they can promote tumor growth and metastasis, while DHA-derived 19,20-epoxydocosapentaenoic acid (19,20-EDP) was shown to have anti-tumor activity in mice. In this pilot study, we assessed the effect of sorafenib treatment on the presence of lipid mediators, such as EETs, in blood of the patients with HCC using the lipidomics technology. We found a significant increase in 11,12-EET and 14,15-EET levels in HCC patients treated with sorafenib. Furthermore, while not significant in this small sample set, the data presented indicate that sorafenib can also increase the level of omega-3 DHA-derived 19,20-EDP. While the effect on EETs might hamper the anti-tumor effect of sorafenib, we hypothesize that supplementation of DHA in sorafenib-treated HCC patients could increase the level of 19,20-EDP and thereby enhance its anti-tumor effect.

Study on Catalytic Synthesis of Low Molecular Weight Polyether Polyol by Composite Alkaline Earth Metal

Polyether Polyol is one of the main intermediates in the synthesis of polyurethane. This research work investigated the optimization of polyether polyol from propylene oxide using Single Factor Experiments and Response Surface Methodology (RSM) through composite alkaline earth metal catalyst (BaO/MgO/γ-Al2O3). The BaO/MgO/γ-Al2O3 catalyst was prepared with alkaline earth metal oxide immobilized on γ-Al2O3 by co-precipitation method. The preparation conditions of the catalysts is calcination temperature=600 °C, n(Ba):n(Al)=0.1:1, n(Mg):n(Al)=0.3:1. Represented with XRD, SEM, BET, CO2-TPD, etc. Characterization results showed that the catalysts indicated strong basic site, perfect particle surface area, pore volume, pore size and relatively uniform particle size distribution. Batch analyses demonstrated that the polyether molecular weight and the epoxide conversion was highly influenced by different process factors which include reaction temperature, pressure, time and the amount of catalyst. The conversion of propylene oxide and molecular weight to target product reached almost 63.5% and 600, respectively under the conditions of reaction temperature 190 °C, pressure 2 MPa, time 6 h and catalyst dosage 6%.

New efficient tetraphenyl silylated poly(azomethine)s based on “pincer-like” bis(imino)pyridine iron(III) complexes as heterogeneous catalysts for CO2 conversion

Aromatic poly(azomethine)s containing simultaneously for the first time both tetraphenyl silane moeties and “pincers” of bis(imino)pyridine were prepared, to provide these polymers with a robust structure and ability to anchor metals. The polymers were prepared from difunctional monomers which provide an special conformation yielding moderate surface areas (up to 60 m2/g). The insolubility and further incorporation of iron to these polymers have generated a new set of heterogeneous catalysts with high metal content, high thermal stability and with excellent catalytic performance in the cycloaddition of CO2 to epoxides to form cyclic carbonates. Very small amounts of catalysts work efficiently, in the absence of solvent, at moderate CO2 pressures (3 bar) showing very high yields of epoxide conversion (up to 95%), 100% of selectivity to the corresponding cyclic carbonate in all cases and high turn-over numbers (up to 7000) being reused at least five times with no apparent loss in catalytic activity. The new catalysts are more efficient than a similar catalyst previously reported for this conversion and work in milder conditions.

Ti(IV)-Tris(phenolate) Catalyst Systems for the Ring-Opening Copolymerization of Cyclohexene Oxide and Carbon Dioxide.

Titanium(IV) complexes of amino-tris(phenolate) ligands (LTiX, X = chloride, isopropoxide) together with bis(triphenylphosphine)iminium chloride (PPNCl) are active catalyst systems for the ring-opening copolymerization of carbon dioxide and cyclohexene oxide. They show moderate activity, with turnover frequency values of ∼60 h–1 (0.02 mol % of catalyst, 80 °C, 40 bar of CO2) and high selectivity (carbonate linkages >90%), but their absolute performances are lower than those of the most active Ti(IV) catalyst systems. The reactions proceed with linear evolution of polycarbonate (PCHC) molar mass with epoxide conversion, consistent with controlled polymerizations, and evolve bimodal molar mass distributions of PCHC (up to Mn = 42 kg mol–1). The stoichiometric reaction between [LTiOiPr] and tetraphenylphosphonium chloride, PPh4Cl, allows isolation of the putative catalytic intermediate [LTi(OiPr)Cl]−, which is characterized using single-crystal X-ray diffraction techniques. The anionic titanium complex [LTi(OR)Cl]− is proposed as a model for the propagating alkoxide intermediates in the catalytic cycle.

Synthesis of bio-based cyclic carbonate from vegetable oil methyl ester by CO2 fixation with acid-base pair MOFs

Bio-based five-membered cyclic carbonates were synthesized from renewable O-acetyl methyl ricinoleate that from crops and CO2 via two steps and the products after each reaction step were characterized by fourier transform infrared spectroscopy. For the acid-catalyzed process, O-acetyl methyl ricinoleate epoxidation of unsaturated double bonds was accomplished using lipase as a sustainable replacement. The effect of different experimental conditions, including the solvent, initiator types, initiator ratios, enzyme amount, reaction temperature, and reaction time, on epoxide conversion was analyzed. O-acetyl methyl ricinoleate conversion reached 95 % under the optimized reaction conditions and the resulting epoxide was subsequently reacted with CO2 using the acid-base pair UiO-66-NH2 to produce cyclic carbonate. CO2 adsorption and fixation occurred simultaneously due to the use of bifunctional UiO-66-NH2 and epoxide conversion reached 94.4 % with CO2 using UiO-66-NH2. The substrates applicability was tested after each step and it was found that more than 92 % of the fatty acid methyl esters were converted into their corresponding epoxides and more than 90 % epoxide conversion occurred, with the exception of epoxy methyl linolenate (85.4 %) due to the presence of multiple double bonds in methyl linolenate. These results demonstrate this reaction scheme can be efficiently adopted for vegetable oil methyl esters.

1,2‐Diketones as photoinitiators of both cationic and free‐radical photopolymerization under UV (392 nm) or Blue (455 nm) LEDs

ABSTRACTThe photoinitiation abilities of three 1,2‐diketones [i.e., acenaphthenequinone (ANPQ), aceanthrenequinone (AATQ), and 9,10‐phenanthrenequinone (PANQ)]‐based photoinitiating systems [PISs, with additives such as iodonium salt, N‐vinylcarbazole (NVK), tertiary amine, and phenacyl bromide (R‐Br)] for cationic photopolymerization and free‐radical photopolymerization under the irradiation of ultraviolet (UV; 392 nm) or blue (455 nm) light‐emitting diode (LED) bulb are investigated. All 1,2‐diketones studied exhibit ground state absorption that match with the emission spectra of UV (392 nm) or blue LED (455 nm) better than that of the well‐known blue‐light‐sensitive photoinitiator camphorquinone (CQ). In particular, AATQ/iodonium salt/NVK can show high photoinitiating ability (with epoxide conversion yield >70%) under the UV light irradiation due to the effect of NVK. In addition, 1,2‐diketone/iodonium salt (and optional NVK) systems are capable of initiating free‐radical photopolymerization of methacrylates, with conversions of 50–58%. Furthermore, some 1,2‐diketone/tertiary amine (and optional R‐Br) combinations are found to demonstrate high efficiency to initiate free‐radical photopolymerization, and 71% of methacrylate conversion can be achieved with PANQ/tertiary amine/R‐Br PIS. Some 1,2‐ketone‐based PISs can even exhibit higher efficiency than the CQ‐based systems. The photochemical mechanism of the radical generation from the 1,2‐diketone‐based PISs is investigated and found to be consistent with the related photopolymerization efficiency. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 792–802

Metalated-bipyridine-based porous hybrid polymers with POSS-derived Si-OH groups for synergistic catalytic CO2 fixation.

Herein, we construct a new series of N-heterocyclic ligand bipyridine-based porous hybrid polymers (denoted Bpy-PHPs) from the Heck reaction of a rigid building unit octavinylsilsesquioxane (VPOSS) and 5,5'-dibromo-2,2'-bipyridine. Surprisingly, the typical sample Bpy-PHP-4 was found to be a metal-/halogen-free heterogeneous catalyst in the cycloaddition reaction of CO2 with a few epoxides under atmospheric pressure. After coordination with ZnBr2, the resultant ZnBr2@Bpy-PHP-4 afforded largely enhanced heterogeneous catalytic activities upon the conversion of carbon dioxide (CO2) and various epoxides into cyclic carbonates without using any co-catalysts under mild conditions. The moderate catalytic activities of Bpy-PHP-4 may be due to the presence of hydrogen bond donors (HBDs), i.e., polyhedral oligomeric silsesquioxane (POSS)-derived Si-OH groups and N active sites from Bpy linkers. In comparison, the high catalytic efficiency of ZnBr2@Bpy-PHP-4 should be attributed to the synergistic catalysis of Si-OH groups, N active atoms, and Bpy-coordinated ZnBr2. Moreover, the catalyst ZnBr2@Bpy-PHP-4 can be easily recovered and reused ten times without any significant loss of catalytic activities. This work affords an efficient metal-based porous hybrid polymer heterogeneous catalyst for the cycloaddition reaction of CO2 and epoxides under mild and co-catalyst-free conditions.