Catalytic Glucose Isomerization by Porous Coordination Polymers with Open Metal Sites

Highly efficient catalytic isomerization reactions from glucose to fructose in aqueous media using porous coordination polymers (PCPs) or metal–organic frameworks (MOFs) is reported for the first time. The catalytic activity of PCPs functionalized with ? NH₂, ? (CH₃)₂, ? NO₂, and ? SO₃H groups on the pore surface is systematically tested. The catalytic activity can be tuned by the acidity of open metal sites (OMSs) by modifying the organic linkers with the functional groups. As a result, it is demonstrated that MIL‐101 functionalized with ? SO₃H not only shows high conversion of glucose but also selectively produces fructose. Further, catalytic one‐pot conversion of amylose to fructose is achieved, thanks to the high stability of the framework in an acidic solution. These results show that MOF/PCP compounds having OMSs are promising materials for various useful heterogeneous catalytic reactions, in particular in the biomass field.     

The synthesis and study of the physicochemical and catalytic properties of composites with the sulfated perfluoropolymer/carbon nanofiber composition

Composites with the sulfated perfluoropolymer (SFP) (Nafion, etc.)—mesoporous support composition (SFP/support)—are promising solid acid catalysts with strong acid sites and very stable sulfo groups towards leaching processes. The effect of the SFP on the carbon nanofiber (CNF) (SFP/CNF) composite synthesis method, as well as the precursors of the acid phase, on the key acid catalyst characteristics (specific surface area and concentration and accessibility of the acid sites) is studied. The possibility of the direct composite synthesis from SO₂F-polymer latexes obtained as a result of the water emulsion SFP synthesis (without the intermediate stages of isolating the SO₃H form) is shown. The acid phase precursor types which are acceptable for the SFP/CNF composite synthesis (the equivalent polymer weight > 580 g/mol) are selected. The effect of the amount of the supported polymer on the total specific surface area and concentration and accessibility of the composite acid site is investigated. The structure of the synthesized composites is studied (by TEM, SAXS, and isopropanol TPD), and their catalytic activity in the test acetic acid esterification reaction is compared to the catalytic activity of pure polymer samples and acetic acid. It is found that the synthesized SFP/CNF samples outperform commercial SFP/SiO₂ samples (SAC, DuPont), as well as the SFP/CNF samples prepared using polymer solutions in the SO₃H form, in terms of the catalytic characteristics.     

Solid Polymer Electrolytes Studied by NMR Spectroscopy and DFT Calculations

Summary: Results obtained recently on polymer electrolytes poly(ethylene oxide) (PEO)/LiCF₃SO₃ and poly(2-ethyl-2-oxazoline) (POZ)/AgCF₃SO₃ by a combination of solid-state ¹³C and ¹H NMR spectroscopy and DFT quantum-chemical calculations are discussed. Essentially the same local structure was found for the amorphous and crystalline phases of semicrystalline PEO/LiCF₃SO₃ polymer electrolyte. The amorphous POZ/AgCF₃SO₃ complex has a defined stoichiometry with two POZ monomeric units per one AgCF₃SO₃. A close contact between the metal salt and polymer was determined for both investigated systems from the Lee-Goldburg cross-polarization ¹H → ¹³C dynamics.     

Morphology Tailoring of Sulfonic Acid Functionalized Organosilica Nanohybrids for the Synthesis of Biomass‐Derived Alkyl Levulinates

Morphology evolution of sulfonic acid functionalized organosilica nanohybrids (Si(Et)Si‐Pr/ArSO₃H) with a 1D tubular structure (inner diameter of ca. 5 nm), a 2D hexagonal mesostructure (pore diameter of ca. 5 nm), and a 3D hollow spherical structure (shell thickness of 2–3 nm and inner diameter of ca. 15 nm) was successfully realized through P123‐templated sol–gel cocondensation strategies and fine‐tuning of the acidity followed by aging or a hydrothermal treatment. The Si(Et)Si‐Pr/ArSO₃H nanohybrids were applied in synthesis of alkyl levulinates from the esterification of levulinic acid and ethanolysis of furfural alcohol. Hollow spherical Si(Et)Si‐Pr/ArSO₃H and hexagonal mesoporous analogues exhibited the highest and lowest catalytic activity, respectively, among three types of nanohybrids; additionally, the activity was influenced by the ?SO₃H loading. The activity differences are explained in terms of different Brønsted acid and textural properties, reactant/product diffusion, and mass transfer rate, as well as accessibility of ?SO₃H sites to the reactant molecules. The reusability of the nanohybrids was also evaluated.     

酸性功能化离子液体催化合成叶青素

以含磺酸基离子液体1-(4-磺酸基)丁基-3-甲基咪唑四氟硼酸盐([4-sulfbmim][BF₄])为酸性催化剂,由乙缩醛和苯甲醇合成了叶青素。 采用正交实验方法考察了合成条件的影响,固定反应温度为20 ℃条件下,确定优化合成条件为：n(苯甲醇)∶n(乙缩醛)=1∶8,反应时间60 min,催化剂用量为每摩尔苯甲醇4 g,产率为92.2%。 与H₂SO₄催化剂相比[4-sulfbmim][BF₄]的催化活性相对较弱,但综合效果优于H₂SO₄。 [4-sulfbmim][BF₄]循环使用6次,催化活性基本不变。     

Selective vinyl cationic polymerization of monomers with two cationically polymerizable groups. IV. New initiating systems for selective and living polymerization of p-isopropenylphenyl glycidyl ether

A variety of cationic initiators were employed for p-isopropenylphenyl glycidyl ether (IPGE), an α-methylstyrene derivative with an epoxy pendant, and optimum initiators and reaction conditions were evaluated in terms of its selective vinyl polymerization and living polymerization. Despite the coexistence of two cationically polymerizable groups in IPGE, binary initiating systems (HI, CF₃COOH, or CH₃CH(OiBu)-OCOCH₃, each coupled with ZnI₂) and sulfonic acids (CF₃SO₃H and CH₃SO₃H) selectively polymerized the vinyl group of IPGE in CH₂Cl₂ at ?78°C to produce soluble polymers with epoxy pendant groups in high yield. Metal halides (BF₃OEt₂ and AlEtCl₂) polymerized both the vinyl and epoxy groups of IPGE to give crosslinked insoluble polymers. In contrast, under these conditions, the HI/ZnI₂ system also led to a long-lived polymer, the molecular weight of which increased upon addition of a fresh feed of monomer to a completely polymerized reaction mixture, whereas the use of other initiators resulted in nonliving polymers. At higher temperatures (?40 and ?15°C), soluble poly(IPGE) was also obtained with HI/ZnI₂, but the polymer yield decreased with raising temperature, because of the occurrence of termination reaction.     

Ring-opening polymerization of lactones by rare-earth metal triflates and by their reusable system in ionic liquids

The ring-opening polymerizations (ROPs) of lactones catalyzed by rare-earth metal trifluoromethanesulfonates (triflates) (RE(OTf)₃) were examined. Among various complexes, scandium triflate (Sc(OTf)₃) emerged as an effective catalyst in toluene. The ROP of lactones by Sc(OTf)₃ proceeded in a living fashion, and the number of polymer molecules was controlled by the amount of protic additives such as benzyl alcohol and H₂O. In other words, one molecule of Sc(OTf)₃ catalytically produced a number of polymer molecules (up to 40 molecules) depending on the amount of protic additives. The plausible mechanism was depicted as an activated monomer mechanism. The polylactones with a number-average molecular weight over 25,000 were successfully synthesized. Immobilization of RE(OTf)₃ was investigated in three ionic liquids, and cerium triflate (Ce(OTf)₄) showed relatively high catalytic activity in a biphasic system of 1-butyl-3-methylimidazolium hexafluoroantimonate and toluene in the ROP of ?-caprolactone (CL). The ionic liquid containing Ce(OTf)₄ was used, at least three times, in the ROP of CL without losing catalytic activity.     

Features of сhitosan interaction with copper(II) and cobalt(II) tetrasulfophthalocyanines

The interaction of chitosan with copper(II) and cobalt(II) tetrasulfophthalocyanines is studied by spectral methods. The main parameters of binding of chitosan to anionic metal phthalocyanines are determined by Scatchard analysis. It is found that the formation of the polymer complex is considerably contributed by donor?acceptor interactions between the coordinately unsaturated metal phthalocyanine and chitosan amino groups. Сhitosan reacts with a monomeric cobalt(II) tetrasulfophthalocyanine, whereas copper(II) tetrasulfophthalocyanine in its complex with chitosan remains in the dimeric state. The reaction centers responsible for the Cu(SO₃H)₄Pc)₂–chitosan and Co(SO₃H)₄Pc–chitosan complexes are revealed by means of IR spectroscopy.     

Functionalization of polymeric surfaces by simple photoactivation of C?H bonds

A universal photoassisted pathway to functionalize polymeric surfaces is presented by transferring the inert surface sp³ C? H bonds into reactive groups, such as ? SO₃H, ? NH₂, ? SH, and ? COOH. The proposed method uses acetone as photoinitiator and different phenols with a para substituent XR as the reactants. Acetone excited by UV irradiation acts as a pair of scissors cutting both the surface C? H bonds of the polymer substrate and the O? H bonds of phenol, leading to the formation of carbon‐centered surface chain free radicals and oxygen‐centered phenoxy free radicals. By coupling of these two radicals, a variety of functional X groups with an R spacer from XR species of different phenol reactants were readily bonded to the polymeric surfaces, where phenol reactants included 4‐hydroxylbenzene sulfonic acid for ? SO₃H, p‐aminophenol and tyramine for ? NH₂, 4‐hydroxythiophenol for ? SH, and tyrosine for ? COOH. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Nano‐WO3‐SO3H as a New Photocatalyst Insight Through Covalently Grafted Brønsted Acid: Highly Efficient Selective Oxidation of Benzyl Alcohols to Aldehydes

Modification of nano‐WO₃ with ?SO₃H groups as a covalently grafted solid acid reduced its band‐gap energy from 2.8 to 2.4 eV and made it an ideal nominee for photocatalytic reaction under visible light irradiation. This nano‐photocatalyst has been successfully used for the selective oxidation of different benzyl alcohols to corresponding aldehydes under blue LED irradiation. The reaction became approximately two times faster with excellent yields. It has shown that the nitrobenzene as an available industrial oxidant is applicable for photocatalytic oxidation of benzyl alcohol; remarkably high yield and selectivity have been observed.     

Electrocatalytic properties of nanocomposites based on conducting polymers and titanium dioxide in oxygen reduction process

Electrochemical characteristics and electrocatalytic properties in the oxygen reduction reaction are studied on hybrid nanocomposites based on conducting polymers (polyaniline, polypyrrol) doped with phosphomolybdic acid (PMA), and TiO₂ and also their bifunctional analogs containing up to 5 wt % of nanosize platinum. It is found that the obtained nanocomposites in 0.5 M H₂SO₄ are capable of reversible electro-chemical redox transitions (in the range of potentials from ?0.6 to 1.0 V vs. Ag/AgCl), in which the main contribution is provided by the corresponding conducting polymer and dopant (PMA). It is shown that activity of the studied nanocomposites in the oxygen reduction reaction is caused by the joint catalytic effect of all their components: the polymer, TiO₂, H₃PMo₁₂O₄0, Pt.     

A new catalytic system for the copolymerization of dicyclopentadiene with CO: PdCl2/phen/M(CF3SO3)n

A new three-component catalytic system, PdCl₂/phen/M(CF₃SO₃)_n, was studied in the copolymerization of dicyclopentadiene (DCPD) with CO. It was found that the PdCl₂/phen/CF₃SO₃H catalytic system gave a very low catalytic activity, and the PdCl₂/phen/M(CF₃SO₃)_n catalytic system exhibited high activity when M(CF₃SO₃)_n was introduced instead of CF₃SO₃H. The resultant cooligomer was analyzed using various techniques such as FT-IR, ¹H NMR, ¹³C NMR, DSC and TGA. The results indicated that the copolymer was a polyspiroketal (PS) of CO and DCPD. Due to the tension of the ring of DCPD, the degree of copolymerization is low and the degree of crystallinity is also not high. The effects of ligands, M(CF₃SO₃)_n, solvents, 1,4-benzoquinone/PdCl₂ molar ratio, and temperatures on the copolymerization have been discussed in detail. The results showed that this novel catalytic system exhibited highly efficient activity, especially when 1,10-phenanthroline (phen) was used as ligand and Cu(CF₃SO₃)₂ was used as cocatalyst. The corresponding reaction rate was 49 000 g PS/molPd h when the reaction was carried out at 60 °C and 3.0 MPa of CO. The weight average molecular weight (M_w) and the number average molecular weight (M_n) of the resultant cooligomer were 1180 g/mol and 564 g/mol, respectively.     

Novel type of SO3H–functionalized nano‐titanium dioxide as a highly efficient and recyclable heterogeneous nanocatalyst for the synthesis of tetrahydrobenzo[b]pyrans

n ‐Butylsulfonated nano‐titania (n‐TiO₂‐NH‐(CH₂)₄‐SO₃H) as a highly efficient and reusable nanocatalyst was prepared by grafting 2,4‐toluene diisocyanate as a bi‐functional covalent linker onto a nano‐titania support, followed by reduction and then ring opening‐reaction of the synthesized amine with 1,4‐butanesultone. Fourier transform infrared spectroscopy, X‐ray diffraction, field‐emission scanning electron microscopy and thermogravimetric analysis were used to characterize the catalyst. The catalytic activity of n‐TiO₂‐NH‐(CH₂)₄‐SO₃H was evaluated in the synthesis of tetrahydrobenzo[b ]pyrans, which affords high yields. Statistical experimental design was applied as an efficient and powerful method to achieve the optimal conditions for this catalytic reaction leading to high yield. Moreover, the catalyst was recovered and reused at least six times without a significant decrease in catalytic activity.     

Studies on the copolymerization of norbornene with CO catalyzed by a new catalytic system PdCl<Subscript>2</Subscript>/phen/M(CF<Subscript>3</Subscript>SO<Subscript>3</Subscript>)<Subscript>n</Subscript>

A new three-component catalytic system, PdCl₂/phen/M(CF₃SO₃)_n where M = La, Y, Yb, Zn, and Cu, was studied for the copolymerization of norbornene (NBE) with CO to prepare polyketone (PK). It was found that the CF₃SO₃H catalytic system gave a low catalytic activity for the copolymerization of norbornene with CO, but when M(CF₃SO₃)_n was introduced instead of CF₃SO₃H, the PdCl₂/phen/M(CF₃SO₃)_n catalytic system exhibited much higher activity. The effects of ligands, M(CF₃SO₃)_n, solvents, and temperatures on the copolymerization have been discussed in detail. The results showed that with 1,10-phenanthroline (phen) and Cu(CF₃SO₃)₂ used as cocatalysts, the corresponding reaction rate reached 82 000 g PK (mol Pd)⁻¹h⁻¹ when the reaction was carried out in methanol at 90°C and 3.0 MPa of CO, and the weight average molecular weight (M _w) of the resultant copolymer is 1090 g/mol. The copolymer was characterized with various techniques such as FT-IR, ¹HNMR, ¹³CNMR, TGA, and DSC. The infrared spectrum of the product includes two features at 1697 and 1732 cm⁻¹ for the NBE/CO copolymer in CH₃OH that are attributed to carbonyl groups in ketones (repeating unit) and esters (end group), respectively. Due to the tension of the ring of norbornene, the degree of copolymerization is not high. Published in Russian in Kinetika i Kataliz, 2007, Vol. 48, No. 1, pp. 51–58. This article was submitted by the authors in English.     

The Synthesis of Poly(Vinyl Alcohol) Grafted with Fluorinated Protic Ionic Liquids Containing Sulfo Functional Groups

There has been an ongoing need to develop polymer materials with increased performance as proton exchange membranes (PEMs) for middle- and high-temperature fuel cells. Poly(vinyl alcohol) (PVA) is a highly hydrophilic and chemically stable polymer bearing hydroxyl groups, which can be further altered. Protic ionic liquids (proticILs) have been found to be an effective modifying polymer agent used as a proton carrier providing PEMs’ desirable proton conductivity at high temperatures and under anhydrous conditions. In this study, the novel synthesis route of PVA grafted with fluorinated protic ionic liquids bearing sulfo groups (–SO₃H) was elaborated. The polymer functionalization with fluorinated proticILs was achieved by the following approaches: (i) the PVA acylation and subsequent reaction with fluorinated sultones and (ii) free-radical polymerization reaction of vinyl acetate derivatives modified with 1-methylimidazole and sultones. These modifications resulted in the PVA being chemically modified with ionic liquids of protic character. The successfully grafted PVA has been characterized using ¹H, ¹⁹F, and ¹³C-NMR and FTIR-ATR. The presented synthesis route is a novel approach to PVA functionalization with imidazole-based fluorinated ionic liquids with sulfo groups.     

Reactions of the nitrate radical with a series of reduced organic sulphur compounds in air

A 480 L evacuable reaction chamber, equipped with FT-IR spectroscopy on-line and ion chromatography off-line, has been used to study the gas phase reaction between the nitrate radical, NO₃, and the reduced organic sulphur compounds CH₃CH₂SH, (CH₃CH₂)₂S, (CH₃CH₂)₂S₂, and CH₃CH₂SCH₃ in air. The products CH₃CH₂SO₃H, SO₂, H₂SO₄, CH₃CHO, and CH₃CH₂ONO₂ were identified and quantified in the reactions of the first three compounds, CH₃CH₂SH, (CH₃CH₂)₂S, and (CH₃CH₂)₂S₂. The reaction products were CH₃CH₂SO₃H, CH₃SO₃H, SO₂, H₂SO₄, CH₃CHO, and CH₂O in the reaction of CH₃CH₂SCH₃. On the basis of identified reaction products and intermediates observed in the infrared spectra, mechanisms are proposed for the reactions between the NO₃ radical and the four reduced organic sulphur compounds. The results of this study, together with those from previous experiments performed in this laboratory on CH₃SCH₃, CH₃SH, and CH₃SSCH₃ lead to the conclusion that all these species, in the reaction with the NO₃ radical, follow a similar degradation mechanism producing SO₂, H₂SO₄, R? SO₃H, R? CHO, and R? CH₂ONO₂, as the main reaction products. The inital step of the reaction of NO₃ with R? S? R and R? S? H type (R = CH₃, CH₂CH₃) reduced organic sulphur compounds was found to be H-atom abstraction, probably after the formation of an initial adduct. For the reaction between NO₃ and R? S? S? R type compounds, evidence for an addition-decomposition reaction, as the initial steps, was obtained. R? S·, R? S(O)·, and R? S(O)₂· appear to be formed as intermediates in all the reactions. © John Wiley & Sons, Inc.     

HPA decorated Halloysite Nanoclay: An efficient catalyst for the green synthesis of Spirooxindole derivatives

A novel heterogeneous catalyst, HPA@HNTs‐IMI‐SO₃H, was designed and synthesized based on functionalization of halloysite nanotubes with ionic liquid and subsequent incorporation of heteropolyacid. The structure of the catalyst was studied and confirmed by using SEM/EDX, FTIR, XRD, ICP‐AES, TGA, DTGA and BET. Moreover, the catalytic activity of HPA@HNTs‐IMI‐SO₃H was investigated for promoting ultrasonic‐assisted three‐component reaction of isatines, malononitrile or cyanoacetic esters and 1,3‐dicarbonyl compounds to afford corresponding spirooxindole in high yields and short reaction time. The reusability of the catalyst was also studied. Notably, the catalyst could be recovered and reused for three reaction runs. However, reusing for fourth reaction runs led to the decrease of the catalytic activity. Considering leaching test results, that observation was attributed to the leaching of heteropolyacids, which can be induced by ultrasonic irradiation.     

Rhodium‐Catalyzed Dehydrogenative Silylation of Acetophenone Derivatives: Formation of Silyl Enol Ethers versus Silyl Ethers

A series of rhodium–NSiN complexes (NSiN=bis (pyridine‐2‐yloxy)methylsilyl fac‐coordinated) is reported, including the solid‐state structures of [Rh(H)(Cl)(NSiN)(PCy₃)] (Cy=cyclohexane) and [Rh(H)(CF₃SO₃)(NSiN)(coe)] (coe=cis‐cyclooctene). The [Rh(H)(CF₃SO₃)(NSiN)(coe)]‐catalyzed reaction of acetophenone with silanes performed in an open system was studied. Interestingly, in most of the cases the formation of the corresponding silyl enol ether as major reaction product was observed. However, when the catalytic reactions were performed in closed systems, formation of the corresponding silyl ether was favored. Moreover, theoretical calculations on the reaction of [Rh(H)(CF₃SO₃)(NSiN)(coe)] with HSiMe₃ and acetophenone showed that formation of the silyl enol ether is kinetically favored, while the silyl ether is the thermodynamic product. The dehydrogenative silylation entails heterolytic cleavage of the Si?H bond by a metal–ligand cooperative mechanism as the rate‐determining step. Silyl transfer from a coordinated trimethylsilyltriflate molecule to the acetophenone followed by proton transfer from the activated acetophenone to the hydride ligand results in the formation of H₂ and the corresponding silyl enol ether.     

Experimental and numerical study on water sorption over modified mesoporous silica

–SO₃H modified mesoporous silica adsorbent with water sorption capacity and fast desorption kinetics for water sorption was synthesized and studied via a combined experimental and numerical approach. Mesoporous silica was synthesized using sol–gel method in H₂SO₄ medium. The water adsorption isotherms and kinetics over the silica were evaluated by a dynamic water vapor sorption analyzer. Mesoporous silica was modeled using annealing simulation with CVFF forcefield. –SO₃H modified mesoporous silica was modeled by the attachment of –SO₃H to the surface hydroxyl groups and validated. Simulation results show water sorption capacity at low relative humidity (RH) increases with –SO₃H loading on mesoporous silica. Energy distribution of intermolecular interaction and micro-view of water sorption over –SO₃H modified mesoporous silica reveal that although strong interaction (intermolecular interaction of ?40 to ?20 kcal/mol) between hydrophilic groups (–SO₃H) with water can increase water sorption capacity at low RH, weak H₂O–H₂O interaction (intermolecular interaction of ?20 to ?10 kcal/mol) dominated water sorption capacity at both low and high RH.     

Bimetallic Nanoparticles in Supported Ionic Liquid Phases as Multifunctional Catalysts for the Selective Hydrodeoxygenation of Aromatic Substrates

Bimetallic iron–ruthenium nanoparticles embedded in an acidic supported ionic liquid phase (FeRu@SILP+IL‐SO₃H) act as multifunctional catalysts for the selective hydrodeoxygenation of carbonyl groups in aromatic substrates. The catalyst material is assembled systematically from molecular components to combine the acid and metal sites that allow hydrogenolysis of the C=O bonds without hydrogenation of the aromatic ring. The resulting materials possess high activity and stability for the catalytic hydrodeoxygenation of C=O groups to CH₂ units in a variety of substituted aromatic ketones and, hence, provide an effective and benign alternative to traditional Clemmensen and Wolff–Kishner reductions, which require stoichiometric reagents. The molecular design of the FeRu@SILP+IL‐SO₃H materials opens a general approach to multifunctional catalytic systems (MM′@SILP+IL‐func).