Full Conversion Research Articles

Fast Visible-Light 3D Printing of Conductive PEDOT:PSS Hydrogels.

Functional inks for light-based 3D printing are actively being searched for being able to exploit all the potentialities of additive manufacturing. Herein, a fast visible-light photopolymerization process is showed of conductive PEDOT:PSS hydrogels. For this purpose, a new Type II photoinitiator system (PIS) based on riboflavin (Rf), triethanolamine (TEA), and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is investigated for the visible light photopolymerization of acrylic monomers. PEDOT:PSS has a dual role by accelerating the photoinitiation process and providing conductivity to the obtained hydrogels. Using this PIS, full monomer conversion is achieved in less than 2min using visible light. First, the PIS mechanism is studied, proposing that electron transfer between the triplet excited state of the dye (3 Rf*) and the amine (TEA) is catalyzed by PEDOT:PSS. Second, a series of poly(2-hydroxyethyl acrylate)/PEDOT:PSS hydrogels with different compositions are obtained by photopolymerization. The presence of PEDOT:PSS negatively influences the swelling properties of hydrogels, but significantly increases its mechanical modulus and electrical properties. The new PIS is also tested for 3D printing in a commercially available Digital Light Processing (DLP) 3D printer (405nm wavelength), obtaining high resolution and 500µm hole size conductive scaffolds.

Ketyl Radical Anion Mediated Radical Polymerization and Anionic Ring-Opening Polymerization to Give Polymers with Low Molecular Weight Distribution.

The development of novel polymerization capable of yielding polymers with low molecular weight distribution (Đ) is essential and significant in polymer chemistry, where monofunctional initiator contains only one initiation site in these polymerizations generally. Here, ketyl radical anion species is introduced to develop a novel Ketyl Mediated Polymerization (KMP), which enables radical polymerization at carbon radical site and anionic ring-opening polymerization at oxygen anion site, respectively. Meanwhile, polymerization and corresponding organic synthesis generally couldn't be performed simultaneously in one pot. Through KMP, organic synthesis and polymerization are achieved in one pot, where small molecules (cyclopentane derivates) and polymers with low Đ are successfully prepared under mild condition simultaneously. At the initiation step, both organic synthesis and polymerization are initiated by single electron transfer reaction with ketyl radical anion formation. Cyclopentane derivates are synthesized through 3-3 coupling reaction and cyclization. Polystyrene and polycaprolactone with low Đ and a full monomer conversion are prepared by KMP via radical polymerization and anionic ring-opening polymerization, respectively. This work therefore enables both organic synthesis and two different polymerizations from same initiation system, which saves time, labour, resource and energy and expands the reaction mode and method libraries of organic chemistry and polymer chemistry.

Ketyl Radical Anion Mediated Radical Polymerization and Anionic Ring‐Opening Polymerization to Give Polymers with Low Molecular Weight Distribution

AbstractThe development of novel polymerization capable of yielding polymers with low molecular weight distribution (Đ) is essential and significant in polymer chemistry, where monofunctional initiator contains only one initiation site in these polymerizations generally. Here, ketyl radical anion species is introduced to develop a novel Ketyl Mediated Polymerization (KMP), which enables radical polymerization at carbon radical site and anionic ring‐opening polymerization at oxygen anion site, respectively. Meanwhile, polymerization and corresponding organic synthesis generally couldn't be performed simultaneously in one pot. Through KMP, organic synthesis and polymerization are achieved in one pot, where small molecules (cyclopentane derivates) and polymers with low Đ are successfully prepared under mild condition simultaneously. At the initiation step, both organic synthesis and polymerization are initiated by single electron transfer reaction with ketyl radical anion formation. Cyclopentane derivates are synthesized through 3–3 coupling reaction and cyclization. Polystyrene and polycaprolactone with low Đ and a full monomer conversion are prepared by KMP via radical polymerization and anionic ring‐opening polymerization, respectively. This work therefore enables both organic synthesis and two different polymerizations from same initiation system, which saves time, labour, resource and energy and expands the reaction mode and method libraries of organic chemistry and polymer chemistry.

Hydrothermal stable Ni nanoparticles encapsulated in carbon for hydrothermal hydrogenation of long-chain fatty acids to alkanes

Upgrading bio-oil to hydrocarbon fuels has been a research focus in the field of renewable energy. However, preparing catalysts with high activity, low cost, and high hydrothermal stability poses enormous challenges. In this work, nickel nanoparticles (Ni NPs) encapsulated in carbon are synthesized with an extremely simple scheme and used to catalyze palmitic acid to alkanes through a one-pot method in aqueous phase. The Ni0.5@C0.5 catalyst is highly efficient at achieving full conversion from palmitic acid at 280 °C within 120 min, and the yield of alkanes reached up to 97.9% and exhibited superior hydrothermal stability. Research results indicate that highly dispersed Ni0 is the active site of the catalyst. The coating structure with a graphitic layer provides the guarantee of hydrothermal stability of the catalyst. Firstly, the carbon layer can effectively avoid direct exposure of metal to high-temperature water, and inhibit metal leaching. In addition, the internal carbon layer separates and disperses Ni NPs and inhibits aggregation. Moreover, the Ni0.5@C0.5 catalyst is suitable for the hydrothermal hydrogenation of various fatty acids/methyl esters. This work provides a new strategy for obtaining catalysts with excellent hydrothermal stability and improving the catalytic activity of bio-oil deoxygenation.

Ruthenium, rhodium and iridium complexes of a silyl-substituted N-heterocyclic carbene ligand and their catalytic performance in hydrosilylation of terminal alkynes

Herein, [Ru(NHC)(p-cymene)Cl2] (3) and [MCl(NHC)(cod)] (M=Rh (4) or Ir (5)) (cod=1,5‒cyclooctadiene) complexes of a silyl‒substituted N-heterocyclic carbene ligand (NHC) have been prepared by the transmetalation reaction between Ag‒NHC (2) and corresponding starting metal compound. The characterization of the complexes has been completed by NMR spectroscopy and elemental analyses. Solid state structures of Ag- (2) and Rh-NHC (4) have also been determined by single crystal X-ray analysis. [RhCl(NHC)(CO)2] type bis-carbonyl complex (6) has also been prepared and CO stretching frequencies pointed the strong σ‒donor ability of the silyl-substituted NHC. The catalytic activity of all complexes have been examined in hydrosilylation of terminal alkynes. Among the complexes, Ir-NHC has been found out as active catalyst with around 90% conversion and β‒(Z) selectivity at room temperature. Further studies revealed that this complex is able to maintain its stability in catalytic reaction conditions, chemoselective to alkynes in the presence of alkenes, and operable in scale-up reactions. In contrast, bis-carbonyl Rh-NHC performed 82% β‒(Z) selectivity with full conversion of alkyne in first 4 h of reaction, but when reaction time was extended to 24 h, almost all β‒(Z) vinylsilane isomerised to thermodynamically more stable β‒(E).

One-pot ternary sequential reactions for photopatterned gradient multimaterials

One-pot ternary sequential reactions for photopatterned gradient multimaterials

Photo-Oxidation in Three-Phase Flow with Continuous Photosensitizer Recycling

Microreactors have emerged as a promising platform for conducting photo-oxidations, offering green routes to facilitate significant chemical transformations. In this study, the sustainability of photo-oxidations is improved by a three-phase gas/liquid/liquid flow reaction in a photo-microreactor with continuous recycling, which is applied to a model reaction. Recycling is enabled by the photosensitizer and the substrate, which are in immiscible phases. The effect of various operational parameters on the reaction and the contact pattern among phases is explored, and the interplay between the flow pattern and photo-oxidation is discussed. The highest conversion is detected for flow conditions that display significantly lower diffusion distance between the dispersed photosensitizer slug and the oxygen bubble, highlighting the link between the flow pattern and mass transfer. Furthermore, phase separation was automated using a liquid–liquid separator where the photosensitizer and organic substrate were recycled continuously to achieve full conversion. The proposed approach eliminates the downstream purification step and provides a sustainable pathway toward photo-oxidations in microreactors.

Oxidation coupling of terminal alkynes over CuPd bimetallic alloy enhanced by optimized charge transfer and alloy structure

Homocoupling of terminal alkynes is an effective approach for the synthesis of 1,3-diyne, which is an important building block for numerous fine chemicals and pharmaceuticals. However, this reaction frequently encounters difficulties in catalyst recovery, and requires the addition of base or organic ligands, limiting their practical applications. Herein, we developed an efficient and recyclable CuPd bimetallic nanoalloy catalyst, which exhibited superior activity and selectivity in the homocoupling of terminal alkynes under mild conditions without any additives. In contrast to the low activity of monometallic Cu or Pd catalysts, a full conversion with a 100% selectivity for 1,3-diyne was achieved on bimetallic Cu2Pd1-400 nanoalloy with an extremely high activity. The comprehensive characterizations clearly evidenced that the alloying Cu with Pd was found to perturb the Cu electronic structure, and the positively charged Cu on the step and edge sites of CuPd nanoalloy catalyzed the homocoupling reaction via Cu-acetylide intermediates, and the density functional theory calculations revealed that the desorption of 1,3-diyne on CuPd nanoalloy was the rate-determining step for the whole reaction. This work provides a viable strategy for the rational design and fabrication of other nanoalloy catalysts for the green synthesis related to terminal alkyne oxidation.

In Situ Reconstruction of Helical Iron Borophosphate Precatalyst toward Durable Industrial Alkaline Water Electrolysis and Selective Oxidation of Alcohols

AbstractIron‐based (pre)catalysts have attracted enormous attention for various electrooxidation reactions due to the low cost, high abundance, and multiple accessible redox states of iron. Herein, a well‐defined helical iron borophosphate (LiFeBPO) is developed as an electro(pre)catalyst for the oxygen evolution reaction (OER) and selective alcohol oxidation. When deposited on nickel foam (NF), LiFeBPO exhibits an exceptional OER performance at ambient conditions attaining a current density of 100 mA cm−2 at ≈276 mV overpotential in 1 m KOH. Notably, this anode sustains durable alkaline water electrolysis at 500 mA cm−2 for over 330 h under industrial conditions (6 m KOH and 85 °C). In –situ and ex situ investigations reveal a deep reconstruction of LiFeBPO during OER, which transforms into a 3D open porous skeleton assembled by ultrasmall, low‐crystalline α‐FeOOH nanoparticles (interfacing with NiOOH of NF). This structure contributes to exposing accessible surface active sites, as well as accelerating mass transport and bubble detachment. Moreover, this electrode also catalyzes the electrooxidation of alcohols (methanol, ethylene glycol, and glycerol) to formic acid (FA) with high selectivity and full conversion. This study provides promising solutions for designing suitable anodes for the simultaneous production of green hydrogen fuel and value–added FA from electrooxidation reactions.

Building Blocks and COFs Formed in Concert—Three‐Component Synthesis of Pyrene‐Fused Azaacene Covalent Organic Framework in the Bulk and as Films

AbstractA three‐component synthesis methodology is described for the formation of covalent organic frameworks (COFs) containing extended aromatics. Notably, this approach enables synthesis of the building blocks and COF along parallel reaction landscapes, on a similar timeframe. The use of fragmental building block components, namely pyrene dione diboronic acid as aggregation‐inducing COF precursor and the diamines o‐phenylenediamine (Ph), 2,3‐diaminonaphthalene (Naph), or (1R,2R)‐(+)‐1,2‐diphenylethylenediamine (2Ph) as extending functionalization units in conjunction with 2,3,6,7,10,11‐hexahydroxytriphenylene, resulted in the formation of the corresponding pyrene‐fused azaacene, i.e., Aza‐COF series with full conversion of the dione moiety, long‐range order, and high surface area. In addition, the novel three‐component synthesis was successfully applied to produce highly crystalline, oriented thin films of the Aza‐COFs with nanostructured surfaces on various substrates. The Aza‐COFs exhibit light absorption maxima in the blue spectral region, and each Aza‐COF presents a distinct photoluminescence profile. Transient absorption measurements of Aza‐Ph‐ and Aza‐Naph‐COFs suggest ultrafast relaxation dynamics of excited‐states within these COFs.

Building Blocks and COFs Formed in Concert-Three-Component Synthesis of Pyrene-Fused Azaacene Covalent Organic Framework in the Bulk and as Films.

A three-component synthesis methodology is described for the formation of covalent organic frameworks (COFs) containing extended aromatics. Notably, this approach enables synthesis of the building blocks and COF along parallel reaction landscapes, on a similar timeframe. The use of fragmental building block components, namely pyrene dione diboronic acid as aggregation-inducing COF precursor and the diamines o-phenylenediamine (Ph), 2,3-diaminonaphthalene (Naph), or (1R,2R)-(+)-1,2-diphenylethylenediamine (2Ph) as extending functionalization units in conjunction with 2,3,6,7,10,11-hexahydroxytriphenylene, resulted in the formation of the corresponding pyrene-fused azaacene, i.e., Aza-COF series with full conversion of the dione moiety, long-range order, and high surface area. In addition, the novel three-component synthesis was successfully applied to produce highly crystalline, oriented thin films of the Aza-COFs with nanostructured surfaces on various substrates. The Aza-COFs exhibit light absorption maxima in the blue spectral region, and each Aza-COF presents a distinct photoluminescence profile. Transient absorption measurements of Aza-Ph- and Aza-Naph-COFs suggest ultrafast relaxation dynamics of excited-states within these COFs.

Solvent-Free Heterogeneous Catalytic Hydrogenation of Polyesters to Diols.

The utilization of carbon resources stored in plastic polymers through chemical recycling and upcycling is a promising approach for mitigating plastic waste. However, most current methods for upcycling suffer from limited selectivity towards a specific valuable product, particularly when attempting full conversion of the plastic. We present a highly selective reaction route for transforming polylactic acid (PLA) into 1,2-propanediol utilizing a Zn-modified Cu catalyst. This reaction exhibits excellent reactivity (0.65 g gcat -1 h-1 ) and selectivity (99.5 %) towards 1,2-propanediol, and most importantly, can be performed in a solvent-free mode. Significantly, the overall solvent-free reaction is an atom-economical reaction with all the atoms in reactants (PLA and H2 ) fixed into the final product (1,2-propanediol), eliminating the need for a separation process. This method provides an innovative and economically viable solution for upgrading polyesters to produce high-purity products under mild conditions with optimal atom utilization.

Solvent‐Free Heterogeneous Catalytic Hydrogenation of Polyesters to Diols

AbstractThe utilization of carbon resources stored in plastic polymers through chemical recycling and upcycling is a promising approach for mitigating plastic waste. However, most current methods for upcycling suffer from limited selectivity towards a specific valuable product, particularly when attempting full conversion of the plastic. We present a highly selective reaction route for transforming polylactic acid (PLA) into 1,2‐propanediol utilizing a Zn‐modified Cu catalyst. This reaction exhibits excellent reactivity (0.65 g gcat−1 h−1) and selectivity (99.5 %) towards 1,2‐propanediol, and most importantly, can be performed in a solvent‐free mode. Significantly, the overall solvent‐free reaction is an atom‐economical reaction with all the atoms in reactants (PLA and H2) fixed into the final product (1,2‐propanediol), eliminating the need for a separation process. This method provides an innovative and economically viable solution for upgrading polyesters to produce high‐purity products under mild conditions with optimal atom utilization.

One step synthesis of novel CuS-ZnS/SiO2@n-octadecane nanocapsules with full spectral absorption range and high photothermal conversion efficiency

In this manuscript, CuS-ZnS/SiO2@n-octadecane nanocapsules were prepared by a simple one-step Cu2+ and Zn2+ co-deposition method. The results of XRD, SEM, TEM, FTIR and XPS show that nanocapsules composed of CuS-ZnS/SiO2 shell and n-octadecane core material were successfully prepared, and the particles deposited was proved to be composite structure of CuS-ZnS. The solution concentration, reaction temperature and pH value have significant effects on the morphology of the nanocapsules prepared. The appropriate conditions are 0.02 mol/L CuSO4, 0.02 mol/L Zn(CH3COO)2, 60 °C, and no additional pH adjustment. Under the optimum conditions, the melting enthalpy reached 45.11 J/g, and after 100 times of cold and hot cycles, the melting enthalpy of the sample only decreased by 3.2%, showing good thermal stability. The CuS-ZnS composite structure makes CuS-ZnS/SiO2 nanocapsules exhibit a wider spectrum absorption performance. The absorption effect of CuS-ZnS/SiO2 nanocapsules to ultraviolet light is significant, compared to the slight reducing of the visible light, while the absorption of near-infrared light is strong. The photothermal conversion efficiency of the samples is significantly improved from 9.7% to 86.6%. Hence, the prepared nanocapsules achieve full spectral absorption, which has a broad application prospect in solar thermal utilization.

High activities of nickel (II) complexes containing phosphorus-nitrogen ligands in hydrogen transfer reaction of imines using formic acid as a renewable hydrogen source

The catalytic reduction of imines to obtain secondary amines is an important route in the synthesis of molecules of biological or pharmaceutical interest. A series of new nickel (II) complexes bearing phosphorous-nitrogen (P,N) or phosphorous-nitrogen-phosphorous (P,N,P) ligands were characterized and studied as catalysts in hydrogen transfer reaction of imines, using formic acid as a hydrogen source, while avoiding the use of molecular hydrogen (H2). The complexes, of general formula NiCl2(L), [Ni(L)2](CF3SO3)2 (in which L is a P,N ligand) and [NiCl(L)]Cl (in the case of a tridentate PNP ligand), were active catalysts in the imine hydrogen, with turnover frequencies (TOF) up to 373 h−1 with NiCl2L1 complex (L1 = 2-(diphenylphosphinoamino) pyridine) and N-benzylideneaniline as substrate, while a [Ni(L)2](CF3SO3)2 complex bearing the same P,N ligand achieved a slightly lower activity (TOF = 320 h−1). Catalyst recyclability was also studied, achieving near full conversion after four cycles, with a total substrate/catalyst ratio of 1000:1.

Synthesis of Co―N―C catalysts from a glucose hydrochar and their efficient hydrogenation of nitrobenzene

A low-cost, green catalyst for nitrobenzene (NB) hydrogenation is needed for aniline production. We report the preparation of highly-dispersed Co particles supported on N-doped carbons by the hydrothermal treatment of glucose, followed by the pyrolysis of a mixture of urea, glucose hydrochar and cobalt nitrate in one-pot. The effect of the pyrolysis temperature on the microstructure of the catalysts was studied. Results indicated that the activity for NB hydrogenation was highly affected by the surface area, Co-loading level and Co-Nx coordination in the catalysts. Co@NCG-800 pyrolyzed at 800 °C with 10% Co in the precursor had extraordinary activity for NB hydrogenation, achieving full conversion and 99% aniline selectivity in isopropanol at 100 °C and 1 MPa H2 pressure for 2.5 h. NB conversion and aniline selectivity over the catalysts remained almost unchanged after six recycles, due to the strong coordination between the N- and Co-species. The reaction system showed not only a high NB activity but also a green and durable catalytic process, with easy operation, easy separation and catalyst reusability.

Vanadium Catalyst in Micelles: Toward a Greener Aerobic Oxidative Cleavage of Vicinal Diols in Water

Aqueous micellar media offer an alternative to organic solvents for the development of safe and environmentally benign synthesis. A vanadium aminotriphenolate complex, known to be an effective catalyst for the aerobic oxidative C–C cleavage of vicinal diols in organic solvents, was incorporated in zwitterionic dodecyl phosphocholine (DPC) and in mixed TPGS-750-M:DPC micelles. It efficiently performed affording the corresponding carbonyl derivatives with no overoxidation, with catalyst loading down to 0.2 mol % and reaching TONs up to 500. The mixed micelles, which combine the enhanced stability conferred by zwitterionic DPC and the exceptional extraction properties of non-ionic TPGS-750-M, could be recycled and full conversion achieved upon reloading with catalyst and substrate. The study of the correlation between the reactivity of different substrates and their local concentration in the micellar core, derived from DOSY experiments, highlights that, while lipophilicity is important, the ease with which the substrate can access the catalyst, and therefore the location of the catalyst in the micellar phase, must also be considered when trying to rationalize reactivity in micelles.

Efficient Conversion of Methyl Lactate to Methyl Acrylate over Cesium-Modified Al-Rich Beta Zeolites

Dehydration of methyl lactate (ML) obtained from biomass is a sustainable route for the production of methyl acrylate (MA). Herein, we demonstrate that cesium-exchanged Al-rich Beta zeolite (Cs-Beta) is highly efficient for the dehydration of ML to MA, exhibiting full ML conversion with 87.4% MA yield at 340 °C. In situ FT-IR spectra and kinetic studies provide evidence that the ML dehydration on the Cs-Beta zeolite follows a forward ion-exchange/dehydration/reverse ion-exchange reaction pathway. Model experiments, DFT calculations, TG-DSC analysis, and FT-IR spectra showed that coke formation competes with the dehydration of ML to MA. Kinetic studies and theoretical simulations demonstrate that cesium cations in the micropores of Beta zeolite have a strong steric hindrance, suppressing the formation of oligomers and coke. These results offer new insights for developing highly selective and stable catalysts for the dehydration of ML to MA in the future.

Conversion of Methanol into Hydrocarbons over Biomass‐Assisted ZSM‐5 Zeolites: Effect of the Biomass Nature

AbstractBiomass waste was revealed to act as a promising bio‐template to modify and possibly tailor the zeolite intrinsic properties: texture, crystallinity and acidity. According to the “bio‐sourced secondary template (BSST)” concept, 7 types of abundant biomasses (lignin, oxidized lignin, coffee bagasse, spent tea leaves and three kinds of algae) were selected and their role was evaluated in the zeolite crystallization. As‐synthesized biomass‐assisted ZSM‐5 zeolites were characterized by XRD, SEM, BET and NH3‐TPD techniques to investigate the effects of biomass extra‐addition. The results showed that mainly surface acidic properties were impacted by the presence of biomass. Among them, spent tea leaves‐mediated ZSM‐5 (named A‐tea) exhibited a high catalytic performance in the methanol‐to‐olefins reaction (MTO), with full methanol conversion for more than 50 h at 83 % selectivity towards light olefins, probably due to its mild acidity. Besides, more acidic ZSM‐5 zeolites obtained using three algae (algaCM, algaTM and algaBB), according to the B‐method, demonstrated a methanol conversion superior to 50 % during 75, 94 and 134 h, respectively. This study led to synthesize potential catalysts exhibiting a high MTO catalytic performance, as well as providing hints for future investigations aiming to control zeolite nucleation and growth following the BSST strategy.

Assessing nutrient and sediment load reduction potential of vegetation by utilizing the nutrient tracking tool at the field and watershed scale in a Great Lakes priority watershed

PurposeNutrient and sediment pollution of surface waters remains a critical challenge for improving water quality. This study takes a user-friendly field-scale tool and assesses its ability to model at both the field and watershed scale within the Fox River Watershed (FRW), Wisconsin, USA, along with assessing how targeted vegetation implementation could attenuate nutrient and sediment exports.MethodsTo assess potential load reductions, the nutrient tracking tool (NTT) was used with a scoring system to identify areas where vegetation mitigation could be implemented within three selected FRW sub-watersheds. A corn soybean rotation, an implementation of a 10-m-vegetated buffer, a full forest conversion, and tiling were modeled and assessed. The corn–soybean results were aggregated and compared to watershed level gauge data in two sub-watersheds. Edge-of-field data was compared to modeled results using multiple parameterization schemes.ResultsThe agricultural areas that scored higher and were untiled showed greater potential nutrient and sediment export reduction (up to 80 to 95%) when vegetation mitigation was implemented in the model. Field-scale results aggregated to the watershed scale showed disparities between modeled and measured phosphorus exports but modeled sediment exports fell within observed gauge data ranges. Field-specific parameter adjustments resulted in more accurate modeled results compared to measured edge-of-field export data but needed further refinement.ConclusionTargeted mitigation using a vegetation-based scoring system with the NTT model was shown to be a helpful tool for predicting nutrient and sediment reductions. Using a field-scale model aggregated to the watershed scale presents tradeoffs regarding processes found beyond the edge of field.