Solution-phase Catalysts Research Articles

Combining Solid FePc Immobilized on Py-Functionalized Carbon Matrix with Soluble Redox Mediator FePc As an Efficient Cathode Catalyst for Non-Aqueous Li-O2 Batteries

It is important to develop bifunctional catalysts with high activity and stability for reversible oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) in lithium-oxygen (Li-O2) batteries. Recently, the iron phthalocyanine (FePc) complex has been considered a promising candidate for bifunctional (ORR/OER) O2 catalysts due to its low cost, high catalytic properties, and ease of preparation. In this work, two different structural types of FePc-based solution-phase catalysts as soluble redox mediators (SRMs) and solid FePc immobilized on pyridine-functional carbon supports (multi-walled carbon nanotube, MWCNT and graphene, GR) are investigated to evaluate the influence of FePc structural design on their catalytic activity and kinetics.Our work demonstrated that FePc(solid)/Py/MWCNT exhibited better bifunctional catalytic activity than FePc(solid)/Py/GR in the same electrolyte because of the stronger axial bonding between FePc(solid) and Py/MWCNT. The combination of FePc(solid)/Py/MWCNT and FePc(sol) displays the best cyclability, which can be attributed to the highly efficient solid-liquid interface. Moreover, FePc(solid)/Py/MWCNT without FePc(sol) shows the lowest overpotential owing to the surface-grown thin film Li2O2 is structurally less order than the solution-grown toroidal Li2O2.

Redox Mediator with the Function of Intramolecularly Disproportionating Superoxide Intermediate Enabled High‐Performance Li–O2 Batteries (Adv. Energy Mater. 12/2022)

Li–O2 Batteries In article number 2102764, Quanfeng Dong and co-workers propose the use of a high-efficiency redox mediator with the function of mediating superoxide intermediates as a bifunctional solution-phase catalyst for Li–O2 batteries, which provides a useful reference for the design and development of multifunctional O2 catalysts for metal–air batteries.

Immobilization of size variable Au nanoparticles on surfactant-modified silica and their catalytic application toward 4-nitrophenol reduction: A comparative account of catalysis

Galvanic replacement reaction (GRR) is a widely used powerful synthesis technique to produce different hollow nanoparticles. In the present work, As(0) nanoparticles in two different size ranges (e.g. 50±7 and 70±10 nm) are synthesized by sodium borohydride reduction of arsenite under controlled pH, and subsequently they are used as templates for GRR reaction to produce two different sized hollow gold nanoparticles (HGNPs), which are designated as RHGNPs and BHGNPs (because of their red and blue colors respectively), with average diameter 55±7 and 72±7 nm, respectively. The unique feature of the reduction of arsenite to As(0) and not to AsH3, is the control of medium pH at 7-9. Now the use of RHGNPs and BHGNPs in homogeneous phase restricts them to recollect and reuse properly. So a soft solid template, cationic surfactant-modified silica (SMS) having positive charge in the surface has been considered to ‘adsolubilize’ the RHGNPs and BHGNPs. The ionic attraction between negatively charged surface of both the HGNPs (which arises due to the in-situ stabilization by surface adsorbed H2AsO4⁻) and the positively charged SMS holds them tightly. SMS after the adsorption of RHGNPs on to it looks pinkish-red and the material is designated as RG-SMS. Similarly, SMS after the adsorption of BHGNPs looks bluish-purple and the material is called BG-SMS. This is a unique procedure to prepare RG-SMS and BG-SMS. The catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of sodium borohydride has been studied using RG-SMS and BG-SMS (i.e. red and blue HGNPs immobilized in the solid phase) as the catalyst to examine the size effect. While both the nanoparticles exhibit excellent catalytic activity, the smaller particles (Au present in RG-SMS) are observed to be more effective than the larger ones (Au present in BG-SMS). The reaction is carried out with varying catalyst doses and initial 4-NP concentrations and the reaction follows first order kinetics in all cases. The first order rate constant values obtained are 0.0667 min−1 and 0.0257 min−1 for RG-SMS and BG-SMS respectively at a dose of 0.041 g L−1 and at 4-NP concentration 9.9 × 10−5 M. The turnover frequency (TOF) obtained at a dose 0.041 g L−1 are 0.0159 per minute and 0.0079 per min for the catalytic reaction using RG-SMS and BG-SMS, respectively. The results suggest that RG-SMS bears ∼2 times higher catalytic activity than that of BG-SMS. The reusability of both catalysts up to the 4th cycle has been checked. The catalytic activity of the HGNPs in the solution phase and the solid phase (i.e. on SMS) are compared. It has been observed that solution phase catalysts are better in terms of activity but solid supported catalysts are better in terms of their shelf-life and ease of application.

Enhanced Electrochemical Performance of Aprotic Li‐CO2 Batteries with a Ruthenium‐Complex‐Based Mobile Catalyst

Li-CO2 batteries are regarded as next-generation high-energy-density electrochemical devices. However, the greatest challenge arises from the formation of the discharge product, Li2 CO3 , which would accumulate and deactivate heterogenous catalysts to cause huge polarization. Herein, Ru(bpy)3 Cl2 was employed as a solution-phase catalyst for Li-CO2 batteries and proved to be the most effective one screened so far. Spectroscopy and electrochemical analyses elucidate that the RuII center could interact with both CO2 and amorphous Li2 C2 O4 intermediate, thus promoting electroreduction process and delaying carbonate transformation. As a result, the charge potential is reduced to 3.86 V and over 60 discharge/charge cycles are achieved with a fixed capacity of 1000 mAh g-1 at a current density of 300 mA g-1 . Our work provides a new avenue to improve the electrochemical performance of Li-CO2 batteries with efficient mobile catalysts.

MOF selectively catalyzes ethylene dimerization

A simple heat treatment can convert a common metal-organic framework (MOF) to an active catalyst for ethylene dimerization. The resulting solid catalyst could potentially replace the expensive solution-phase catalyst currently used for making the monomer 1-butene, a common ingredient in polybutylene and other polymers (Nat. Commun. 2019, DOI: 10.1038/s41467-019-10013-6). Most large-scale catalytic processes rely on solid catalysts. Compared with solution-phase catalysts, which are often organometallic compounds, solid catalysts do not require solvents and cocatalysts or activators, and they are generally easier and less expensive to separate from the product and reuse. But unlike their liquid-phase counterparts, solid catalysts lack uniform active sites and are therefore prone to making unwanted side products. MOFs could offer the best of both worlds: they are porous solids with molecular order. But making them catalytically active remains challenging. Through a series of tests on a ruthenium-based MOF kn...

Controlling Reversible Expansion of Li2O2 Formation and Decomposition by Modifying Electrolyte in Li-O2 Batteries

Summary The aprotic lithium-oxygen (Li-O2) battery has attracted worldwide attention because of its ultrahigh theoretical energy density. However, its practical application is critically hindered by cathode passivation, large polarization, and severe parasitic reactions. Here, we demonstrate an originally designed Ru(II) polypyridyl complex (RuPC) though which the reversible expansion of Li2O2 formation and decomposition can be achieved in Li-O2 batteries. Experimental and theoretical results revealed that the RuPC can not only expand the formation of Li2O2 in electrolyte but also suppress the reactivity of LiO2 intermediate during discharge, thus alleviating the cathode passivation and parasitic reactions significantly. In addition, an initial delithiation pathway can be achieved when charging in turn; thus, the Li2O2 products can be decomposed reversibly with a low overpotential. Consequently, the RuPC-catalyzed Li-O2 batteries exhibited a high discharge capacity, a low charge overpotential, and an ultralong cycle life. This work provides an alternative way of designing the soluble organic catalysts for metal-O2 batteries.

Reduction of α,ω-Dihalohexanes with Electrogenerated Nickel(I) Salen

A recent study has described the electrocatalytic reduction of 1,6-dibromohexane at a silver electrode.1 To mitigate the costs of silver electrodes, glassy carbon electrodes can be used in the presence of a solution-phase catalyst. [[2,2′-[1,2-Ethanediylbis-(nitrilomethylidyne)]bis[phenolato]-N,N′,O,O′]nickel(I), further referred to as nickel(I) salen, has been used as an electrogenerated catalyst in tandem with glassy carbon electrodes due to its ability to reductively cleave carbon—halogen bonds in organic compounds. Previous studies at glassy carbon electrodes with nickel(I) salen or at silver electrodes have primarily focused on reduction of monohalogenated compounds or linear hydrocarbons substituted at both primary positions with mixed halogens. Catalytic reduction of such straight-chain alkyl halides with electrogenerated nickel(I) salen yielded both straight-chain monomeric and dimeric products in high yields.2 In this study, electrogenerated nickel(I) salen was used to reduce 1,6-dibromohexane, 1,6-diiodohexane, and 1-bromo-6-iodohexane catalytically. These substrates were electrolyzed in the presenece of 0.10 M tetramethylammonium tetrafluoroborate (TMABF4) in N,N-dimethylformamide at a glassy carbon electrode. Cyclic voltammetry indicated that direct reduction of 1,6-dibromohexane and 1,6-diiodohexane occurs respectively at –1.64 and –1.56 V vs. a cadmium mercury amalgam reference electrode (Cd(Hg)) with a potential of –0.76 V vs. an aqueous saturated calomel electrode. In contrast, catalytic cathodic peaks are at –0.92 and –0.97 V vs. Cd(Hg) for 1,6-dibromohexane and 1,6-diiodohexane, respectively, indicating that nickel(I) salen does indeed reduce these substrates electrocatalytically. Controlled-potential (bulk) electrolyses of the halogenated substrates led to minor conversion to cyclohexane and halogenated dimers with significant amounts of starting material remaining in solution. This drastic decrease in yield compared to previous studies is hypothesized to be the result of alkylation of the imino bond on the salen ligand.2,3 Though nickel(II) salen can undergo a reversible, one-electron reduction to form nickel(I) salen, reduction of nickel(II) salen can also create a ligand-reduced radical at the imino bond, thus resulting in alkylation of both imino bonds on the salen ligand during electrolysis.3 This dialkylation is responsible for the decreased yield of reaction products and was confirmed with the aid of liquid chromatography—mass spectrometry. A mechanism is proposed with radical intermediates which result in dialkylated nickel(II) salen. Martin, E. T.; Strawsine, L. M.; Mubarak, M. S.; Peters, D. G., Direct Reduction of 1,2- and 1,6-Dibromohexane at Silver Cathodes in Dimethylformamide. Electrochim. Acta 2015, 186, 369–376.Mubarak, M. S.; Peters, D. G., Homogeneous Catalytic Reduction of α,ω-Dihaloalkanes with Electrogenerated Nickel(I) Salen. J. Electroanal. Chem. 1995, 388, 195–198.Martin, E. T.; McGuire, C. M.; Peters, D. G., Catalytic Reduction of Organic Halides by Electrogenerated Nickel(I) Salen. Electrochem. Soc. Interface 2016, 25, 41–45. Figure 1

Combining homo- and heterogeneous catalysis

Most synthetic catalysts fall squarely into one of two categories—homogeneous or heterogeneous, each with its characteristic strong points. Few catalytic systems capitalize on the best of both worlds. Now, a study led by chemists at Massachusetts Institute of Technology takes a key step in that direction (J. Am. Chem. Soc. 2017, DOI: 10.1021/jacs.7b10723). Heterogeneous catalysts, especially ones used in electrochemistry, tend to be robust metals that efficiently bind reactant molecules and mediate catalytic reactions via electron transfer. But molecular details of the binding and active sites are tough to pin down and their structures often change during reaction. In contrast, the structures of metallo-organic molecules that serve as homogeneous solution-phase catalysts are well studied and can be modified easily via synthesis to tune catalyst performance. When used as electrocatalysts, however, electron transfer from the electrode through the catalyst to the reagent molecule is a stepwise, thermodynamically unfavorable process. To bypass

Molecular system identification for enzyme directed evolution and design.

The rational design of chemical catalysts requires methods for the measurement of free energy differences in the catalytic mechanism for any given catalyst Hamiltonian. The scope of experimental learning algorithms that can be applied to catalyst design would also be expanded by the availability of such methods. Methods for catalyst characterization typically either estimate apparent kinetic parameters that do not necessarily correspond to free energy differences in the catalytic mechanism or measure individual free energy differences that are not sufficient for establishing the relationship between the potential energy surface and catalytic activity. Moreover, in order to enhance the duty cycle of catalyst design, statistically efficient methods for the estimation of the complete set of free energy differences relevant to the catalytic activity based on high-throughput measurements are preferred. In this paper, we present a theoretical and algorithmic system identification framework for the optimal estimation of free energy differences in solution phase catalysts, with a focus on one- and two-substrate enzymes. This framework, which can be automated using programmable logic, prescribes a choice of feasible experimental measurements and manipulated input variables that identify the complete set of free energy differences relevant to the catalytic activity and minimize the uncertainty in these free energy estimates for each successive Hamiltonian design. The framework also employs decision-theoretic logic to determine when model reduction can be applied to improve the duty cycle of high-throughput catalyst design. Automation of the algorithm using fluidic control systems is proposed, and applications of the framework to the problem of enzyme design are discussed.

Electrochemical Properties of Lithium Air Secondary Batteries with Nonaqueous Electrolyte Solution Containing Manganese-Based Organic Complexes As Solution-Phase Catalysts

Introduction Lithium air secondary batteries (LABs) have the highest theoretical energy density among secondary batteries reported so far. However, major problems are poor cycle characteristics and large discharge/charge overpotential. To improve these properties, various kinds of solid-phase catalysts loaded into air electrodes have been reported [1]. One of the significant problems is that the solid-phase catalysts become inactivated gradually because discharge product Li2O2 accumulats on the surface of the air electrode as a result of imperfect decomposition during the charging process after a large number of cycles [2]. Since a solution-phase catalyst dissolved in the electrolyte solution could work stably during the cycles, it would overcome these issues associated with the solid-phase catalyst. Recently, as solution-phase catalysts, transition metal complexes such as manganese phthalocyanine (MnPc) [3], cobalt phthalocyanine (CoPc) [4] have been reported [3-5]. It is necessary to investigate the electrocatalytic activities for various kinds of solution-phase catalysts because the catalytic mechanism is unclear. We focused on manganese-containing salen-type complexes (MnSl) as a new solution-phase catalyst (Fig. 1). The electrochemical properties would be improved by involving oxygen adsorbed on the central Mn-ion site with the reaction over the air electrode [6]. Here, we report discharge/charge properties in LABs using MnSl as solution-phase catalyst. Experimental MnSl [(R,R)-(−)-N,N-Bis(3,5–di–tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese(III)chloride] and MnPc [manganese(II) phthalocyanine] as a reference catalyst were purchased from Sigma-Aldrich Co. LLC. A 2.0 wt% of both catalysts vacuum-dried at 90 °C for 12 h was added to an electrolyte solution of 1.0 mol/l LiTFSA / TEGDME (tetraglyme). Ketjenblack EC-600JD (KB, 80 wt%) and polyvinylidene difluoride (PVdF, 20 wt%) coated on carbon paper (Toray, TGP-H-120) was used as the air electrode. A Li metal sheet was used as the negative electrode. The experimental LAB cell was assembled using a commercial cell (ECC-Air, EL-Cell GmbH). Electrochemical experiments were conducted under galvanostatic condition at 200 mA/g in dry air atmosphere. Current density and discharge/charge capacity were normalized by the mass of the reaction layer (KB + PVdF) in the air electrode. Results and discussion Figure 2 shows the first discharge/charge curves of LAB cells with MnSl, with MnPc catalyst, and whithout the solution-phase catalysts. The cells with MnSl catalyst and MnPc show higher average discharge voltages of 2.64 and 2.55 V and larger discharge capacities of 4903 and 3309 mAh/g, respectively, compared to the cell without the catalysts. In addition, the cell with MnSl catalyst shows lower average charge voltage of 3.93 V and larger charge capacity of 6390 mAh/g than the other cells. These results suggest that the solution-phase catalyst could have electrocatalytic activities. Moreover, the MnSl catalyst exhibits rather higher activity than the conventional catalyst, MnPc. However, with the MnSl catalyst, the first charge capacity was larger than the discharge capacity by about 2000 mAh/g. This behavior suggests that some side reactions might co-occur with the charge (oxygen evolution) reaction in the high-voltage region above 4.0 V. Figure 3 shows SEM images of the air electrodes as prepared and after the first discharge without and with MnSl catalyst. Compared to the electrode surface as prepared shown in Fig. 3(a), the fine sub-micrometer discharge products with similar structures were deposited in a part of the electrode surface both without and with MnSl catalyst as shown in Fig. 3(b) and (c). In particular, there were spherical micrometer structures of the discharge products only with MnSl as shown in Fig. 3(c). MnSl catalyst three-dimensionally catalyzed deposition and decomposition of Li2O2 over the air electrode, which led to significant increase in the capacity. According to the above results, the MnSl catalyst exhibited higher activities than MnPc. One of the reasons might be that the oxygen adsorption on the central metal Mn containing N-Mn-N bonds is stronger in MnSl than in MnPc. At the IMLB meeting, we will also discuss the cycle characteristics of LABs with the MnSl catalyst.

Solution Phase Catalysts for Lithium-Oxygen Batteries

A lithium-oxygen battery (LOB) would deliver the highest energy density of a rechargeable battery. But there is a central problem of catalytic action required for the rechargeable LOB: conventional solid state catalysts are not effective enough to catalyze the multiphase electrochemical reactions on the cathode side. The discharge product Li2O2 is also in solid state; it will accumulate at the catalyst surface and hence block the electrode reactions during the discharge process. Meanwhile, during the charging process, it is also difficult to make good contact between the solid catalyst and Li2O2. Therefore, instead of solid catalysts, some novel solution phase catalysts have been developed to solve the above problems1-3. Here, we present a solution-phase catalyst, iron phthalocyanine (FePc), and provide a mechanism involving iron-oxygen coordination and a redox shuttle across the electrolyte4. The Fe-oxygen coordination and the electron dislocation in the big conjugated structure lowers the energy of the high energy intermediates in the ORR and OER. The dissolved FePc can act as a molecular shuttle of (O2)− species and electrons between the surface of electronically conducting carbon and product Li2O2 particles. With this novel approach, the formation and decomposition of Li2O2 is no longer confined to the carbon surface. The Li2O2blocking effect in the discharge process was greatly depressed. Meanwhile, the redox shuttle mechanism effectively lowers the overpotential during the charging process. Thus, the capacity and cyclability of the battery was improved dramatically. Some other solution phase catalysts based on the redox shuttle mechanism, such as ferrocene-derived compounds and iodine, will also be discussed. The efficiency of various redox couples to oxidize the Li2O2during charging is compared with an oxygen monitoring method. We also show some evidence of side reactions caused by some certain redox shuttle compounds. Reference: (1) Y.H. Chen, S.A. Freunberger, Z.Q. Peng, O. Fontaine & P.G. Bruce, "Charging a Li-O-2 battery using a redox mediator". Nat. Chem., 2013, 5(6),489-494. (2) H.-D. Lim, H. Song, J. Kim, H. Gwon, Y. Bae, K.-Y. Park, J. Hong, H. Kim, T. Kim, Y.H. Kim, X. Lepró, R. Ovalle-Robles, R.H. Baughman & K. Kang, "Superior Rechargeability and Efficiency of Lithium–Oxygen Batteries: Hierarchical Air Electrode Architecture Combined with a Soluble Catalyst". Angewandte Chemie International Edition, 2014, 53(15),3926-3931. (3) B.J. Bergner, A. Schurmann, K. Peppler, A. Garsuch & J. Janek, "TEMPO: A Mobile Catalyst for Rechargeable Li-O2 Batteries". J. Am. Chem. Soc., 2014, 136(42),15054-15064. (4) D. Sun, Y. Shen, W. Zhang, L. Yu, Z. Yi, W. Yin, D. Wang, Y. Huang, J. Wang, D. Wang & J.B. Goodenough, "A Solution-Phase Bifunctional Catalyst for Lithium–Oxygen Batteries". J. Am. Chem. Soc., 2014, 136(25),8941-8946.

Size-selected gold clusters on porous titania as the most "gold-efficient" heterogeneous catalysts.

Research on homogeneous and heterogeneous catalysis is indeed convergent and finds subnanometric particles to be at the heart of catalytically active species. Here, monodisperse gold clusters are deposited from the gas phase onto porous titania generating well-defined model systems and the resulting composite materials exhibit a sharp size-dependency on the number of gold atoms per cluster and exceptionally high-turnovers toward the bromination of 1,4-dimethoxybenzene are observed. This indicates that the deliberate generation of active centres is of utmost importance for the creation of the most "gold-efficient" catalysts.

Catalytic Dioxygen Activation by (Nitro)(meso-tetrakis(2-N-methylpyridyl)porphyrinato)cobalt(III) Cation Derivatives Electrostatically Immobilized in Nafion Films: An Experimental and DFT Investigation

Complexes of the (nitro)( meso-tetrakis(2- N-methylpyridyl)porphyinato)cobalt(III) cation, [LCoTMpyP(2)(NO 2)] (4+), in which L = water or ethanol have been immobilized through ionic attraction within Nafion films (Naf). These immobilized six-coordinate species, [LCoTMPyP(2)(NO 2)/Naf], have been found to catalyze the oxidation of triphenylphosphine in ethanol solution by dioxygen, therefore retaining the capacity to activate dioxygen catalytically without an additional reducing agent as was previously observed in nonaqueous solution for the non-ionic (nitro)cobalt porphyrin analogs. Heating these immobilized six-coordinate species under vacuum conditions results in the formation of the five-coordinate nitro derivatives, [CoTMPyP(2)(NO 2)/Naf] at 85 degrees C and [CoTMPyP(2)/Naf] at 110 degrees C. The catalytic oxidation of gas-phase cyclohexene with O 2 is supported only by the resulting immobilized five-coordinate nitro complex as was previously seen with the corresponding solution-phase catalyst in dichloromethane solution. The simultaneous catalytic oxidation of triphenylphosphine and cyclohexene with O 2 in the presence of the Nafion-bound six-coordinate ethanol nitro complex is also observed; however, this process is not seen for the CoTPP derivative in dichloromethane solution. The oxidation reactions do not occur with unmodified Nafion film or with Nafion-supported [BrCo(III)TmpyP]/Naf or [Co(II)TmpyP]/Naf, indicating the necessity for the nitro/nitrosyl ligand in the oxidation mechanism. The existence of a second reactive intermediate is indicated because the two simultaneous oxidation reactions depend on two distinct oxygen atom-transfer steps having different reactivity. The absence of homogeneous cyclohexene oxidation by the six-coordinate (H 2O)CoTPP(NO 2) derivatives in the presence of Ph 3P and O 2 in dichloromethane solution indicates that the second reactive intermediate is lost by an unidentified route only in solution, implying that the immobilization of it in Nafion allows it to react with cyclohexene. Although direct observation of this species has not been achieved, a comparitive DFT study of likely intermediates in several catalytic oxidation mechanisms at the BP 6-31G* level supports the possibility that this intermediate is a peroxynitro species on the basis of relative thermodynamic accessibility. The alternate intermediates evaluated include the reduced cobalt(II) porphyrin, the dioxygen adduct cobalt(III)-O 2 (-), the oxidized cobalt(II) pi-cation radical, and the nitrito complex, cobalt(III)-ONO.

Time-Resolved Observation of Carbon Nanotube Growth by Using an Environmental TEM

We report in-situ observations of the growth of carbon nanotubes (CNTs) by using an environmental transmission electron microscope (E-TEM). E-TEM is a specially designed transmission electron microscope (TEM) with a dierential pumping system where gas can be flowed into the specimen whilst keeping a high vacuum level in the remainder of the TEM column. In order to grow CNTs, Ni nanoparticles as a catalyst were deposited on holey SiOx-TEM mesh grids by using a solution phase catalyst deposition method. Chemical vapor deposition (CVD) was carried out inside the TEM column by flowing acetylene gas ( 10 mTorr) over the Ni catalyst heated to 600 C. At a given growth condition, the CNTs grew with a serpentine morphology with the growing apex frequently returning to the substrate to become anchored at both ends. The growth durations were observed to be quite short, and the growth rate was estimated to be 0.2 mm/sec, which is relatively fast, at low C2H2 pressures of <10 mTorr. Growth was confirmed to occur at the tip where the nickel catalyst particle is located, rather than at the base of the tube, as suggested in the tip growth model. Both multi-walled CNT and single-walled CNT were synthesized simultaneously under the same reaction conditions. This suggests that the nature of the catalyst still plays an important role in determining the characteristics of the CNT even though these characteristics can be controlled by altering either the reaction temperature or pressure.

Preparation of non-cross-linked polystyrene-supported quaternary ammonium salts and use as phase transfer catalysts under microwave

Non-cross-linked chloromethyl polystyrene (NCPS) with high loading and excellent solubility has been effectively and facilely prepared using radical copolymerization of styrene and p-chloromethyl styrene under microwave irradiation. The NCPS supported quaternary ammonium salts have also been prepared by two different methods: chemical modification reactions on NCPS and one-pot reaction of St, CMS and TBA. The catalysts coupled the advantages of conventional solution phase catalysts and insoluble polymer-supported catalysts, catalyzed some nucleophilic substitution reactions under phase transfer catalysis condition effectively under microwave irradiation.

Efficient Formation of Iron Nanoparticle Catalysts on Silicon Oxide by Hydroxylamine for Carbon Nanotube Synthesis and Electronics

Iron containing nanoparticles are found to spontaneously form on hydroxylated SiO2 substrates when immersed in a freshly mixed aqueous solution of FeCl3 and hydroxylamine. Upon calcination, a submonolayer of uniformly distributed iron oxide nanoparticles can be derived and used to catalyze the growth of single-walled carbon nanotubes by chemical vapor deposition. This simple method affords clean single-walled nanotube films on SiO2. The solution phase catalyst deposition approach allows for submicron scale catalyst patterning. Patterned growth of nanotubes with this catalyst retains high degrees of surface cleanliness and leads to arrays of nanotube electronic devices including field effect transistors. The population of hydroxyl groups on SiO2, reaction time, and pH of the solutions are found to be important to the deposition of nanoparticles through a surface-mediated hydroxylamine/FeCl3 chemistry.

A solution phase catalyst for an enantioselective Diels–Alder reaction

A new chiral catalyst for the enantioselective Diels–Alder reaction has been synthesized, namely [(4S,4′S)-4,4′,5,5′-tetra­hydro-4,4′-diiso­propyl-2,2′-(di­benzyl­methyl­ene)­dioxazole-κ2N,N′]­bis(tri­fluoro­methanesulfonato-κO)copper(II) tetra­hy­dro­furan solvate, [Cu(CF3O3S)2(C27H34N2O2)]·C4H8O. It is used in a model study for comparing solid-phase and solution-phase catalyst activity.

Efficient thermochemical alkane dehydrogenation and isomerization catalyzed by an iridium pincer complex

(i–PrPCP)IrH2 is found to be a remarkably effective solution-phase catalyst for the ‘acceptorless’ thermochemical dehydrogenation of cycloalkanes (and isomerization in the case of cyclodecane), and the first such catalyst reported to effect the dehydrogenation of n-alkanes.