Synthesis and Characterization of Poly(5'-hexyloxy-1',4-biphenyl)-b-poly(2',4'-bispropoxysulfonate-1',4-biphenyl) with High Ion Exchange Capacity for Proton Exchange Membrane Fuel Cell Applications

Proton exchange membrane (PEM) is pivotal for proton exchange membrane fuel cells (PEMFCs). In the present work, a block copolymer with hydrophilic alkyl sulfonated side groups and hydrophobic flexible alkyl ether side groups, poly(5'-hexyloxy-1',4-biphenyl)-b-poly(2',4'-bispropoxysulfonate-1',4-biphenyl) (HBP-b-xBPSBP), is designed and synthesized by copolymerization of the hydrophilic and hydrophobic oligomers. The oligomers are synthesized via a Pd-catalyzed Suzuki cross-coupling of 1,3-dibromo-5-hexyloxybenzene, and 3,3'-[(4,6-dibromo-1,3-phenylene)bis(oxy)]bis(propane-1-sulfonate) or 1,4-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzene. The good solubility and film-forming characteristics are achieved via the introduction of flexible hexyloxy side groups, and high ion exchange capacity (IEC) is achieved via the introduction of high density of alkyl sulfonated side groups. The HBP-b-0.5BPSBP has the highest IEC of 3.17 mmol/g, the highest proton conductivity of 43.5 mS/cm at 95 °C and 90% relative humidity (RH) and low methanol permeability of 6.45×10^-7  cm² /s. Meanwhile, crosslinked HBP-b-xBPSBP exhibits promising water uptake, swelling ratio and low methanol permeability. These characteristics are attributed to the crosslinked structure and the hydrophilic/hydrophobic nanophase separation morphology promoted by the poly(m-phenylene) main chains, flexible alkyl ether groups, and alkyl sulfonated side groups.

Microwave-assisted catalytic conversion of chitin to 5-hydroxymethylfurfural using polyoxometalate as catalyst

The key challenges for converting chitin to 5-hydroxymethylfurfural (5-HMF) include the low 5-HMF yield. Moreover, the disadvantages of traditional acid-base catalysts including complex post-treatment processes, the production of by-products, and severe equipment corrosion also largely limit the large-scale conversion of chitin to 5-HMF. In this view, herein we have demonstrated a microwave aided efficient and green conversion of chitin to 5-HMF while using polyoxometalate (POM) as a catalyst and DMSO/water as solvent. Chitin treated with H2SO4 followed by ball-milling (chitin-H2SO4-BM) was selected as the starting compound for the conversion process. Four different POMs including H3[PW12O40], H3[PMo12O40], H4[SiW12O40] and H4[SiMo12O40] were used as catalysts. Various reaction parameters including reaction temperature, amount of catalyst, mass ratios of water/DMSO and reaction time have been investigated to optimize the 5-HMF conversion. The H4[SiW12O40] catalyst exhibited the highest catalytic performance with 23.1% HMF yield at optimum operating conditions which is the highest among the literature for converting chitin to 5-HMF. Significantly, the disadvantages of the state of the art conversion routes described earlier can be overcome using POM-based catalysts, which makes the process more attractive to meet the ever-increasing energy demands, in addition to helping consume crustacean waste.

Solution-Processed Transparent Conducting Electrodes for Flexible Organic Solar Cells with 16.61% Efficiency

Nonfullerene organic solar cells (OSCs) have achieved breakthrough with pushing the efficiency exceeding 17%. While this shed light on OSC commercialization, high-performance flexible OSCs should be pursued through solution manufacturing. Herein, we report a solution-processed flexible OSC based on a transparent conducting PEDOT:PSS anode doped with trifluoromethanesulfonic acid (CF₃SO₃H). Through a low-concentration and low-temperature CF₃SO₃H doping, the conducting polymer anodes exhibited a main sheet resistance of 35 Ω sq^-1 (minimum value: 32 Ω sq^-1), a raised work function (≈ 5.0 eV), a superior wettability, and a high electrical stability. The high work function minimized the energy level mismatch among the anodes, hole-transporting layers and electron-donors of the active layers, thereby leading to an enhanced carrier extraction. The solution-processed flexible OSCs yielded a record-high efficiency of 16.41% (maximum value: 16.61%). Besides, the flexible OSCs afforded the 1000 cyclic bending tests at the radius of 1.5 mm and the long-time thermal treatments at 85 °C, demonstrating a high flexibility and a good thermal stability.

Hydrogenation of α-Pinene over Platinum Nanoparticles Reduced and Stabilized by Sodium Lignosulfonate

A one-pot clean preparation procedure and catalytic performance of platinum nanoparticles (NPs) reduced and stabilized by sodium lignosulfonate in aqueous solution are reported. No other chemical reagents are needed during the metal reduction and stabilization step, thanks to the active participation of sodium lignosulfonate (SLS). UV-vis, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), 1H NMR, 195Pt NMR, and two-dimensional heteronuclear single-quantum coherence (2D HSQC) NMR studies were thoroughly performed to analyze the formation, particle size, and main lattice planes of NPs, the valence-state changes of the metal, and structural changes of SLS. An ecofriendly selective synthesis of cis-pinane from an abundant renewable natural resource, α-pinene, was developed in the presence of the prepared Pt NP aqueous system. Furthermore, this catalyst system was proved to show easy recovery and stable reusability by five-run tests. The synergistic effect of SLS reduction and stabilization not only avoided the introduction of conventional reducing agents and stabilizers but also made full use of the byproducts of the pulp and paper industry. This proved to be an environmentally friendly method for converting the natural resource α-pinene to cis-pinane.

Sulfonic-acid-functionalized carbon fiber from waste newspaper as a recyclable carbon based solid acid catalyst for the hydrolysis of cellulose

Waste newspaper is one of the most common cellulosic materials. Therefore, effective utilization of this commonly available biomass resource to prepare high-value carbon-based solid acid catalysts is an interesting and meaningful task. In this study we propose a new route for waste newspaper valorization, in which sulfonic-acid-functionalized carbon fiber can be directly produced from waste newspaper as a recyclable carbon based solid acid catalyst (WCSA) for the hydrolysis of cellulose. The as-prepared sulfonic-acid-functionalized carbon fiber contained -SO₃H, -COOH, and phenolic -OH groups and exhibited good catalytic activity for the hydrolysis of cellulose. WCSA prepared under sulfonation conditions at a temperature of 100 °C and for a duration of 10 h has a higher sulfonic acid content. A total reducing sugars (TRS) yield of 58.2% was obtained with a catalyst/microcrystalline cellulose (MCC) ratio of 4 at 150 °C using a reaction time of 6 h. The recycling performance of the WCSA catalyst indicated that the TRS remained almost stable for five cycles during the hydrolysis of cellulose.

Gel-Type and Macroporous Cross-Linked Copolymers Functionalized with Acid Groups for the Hydrolysis of Wheat Straw Pretreated with an Ionic Liquid

Several sulfonated cross-linked copolymers functionalized with hydroxyl and carboxylic groups have been synthesized. The amount of the cross-linking monomer was tailored (from 4% up to 40%) to tune the resulting micro- and nano-morphologies, and two types of catalysts, namely, gel-type and macroreticular catalysts, were obtained. These copolymers were employed in the catalytic hydrolysis of wheat straw pretreated in 1-ethyl-3-methylimidazolium acetate to obtain sugars. Remarkably, the presence of additional oxygenated groups enhances the catalytic performances of the polymers by favoring the adsorption of β-(1,4)-glucans and makes these materials significantly more active than an acidic resin bearing only sulfonic groups (i.e., Amberlyst 70). In addition, the structure of the catalyst (gel-type or macroreticular) appears to be a determining factor in the catalytic process. The gel-type structure provides higher glucose concentrations because the morphology in the swollen state is more favorable in terms of the accessibility of the catalytic centers. The observed catalytic behavior suggests that the substrate diffuses within the swollen polymer matrix and indirectly confirms that the pretreatment based on dissolution/precipitation in ionic liquids yields a substantial enhancement of the conversion of lignocellulosic biomass to glucose in the presence of heterogeneous catalysts.

Biocompatible Conductive Polymers with High Conductivity and High Stretchability

Stretchable electronic materials have drawn strong interest due to their important applications in areas such as bioelectronics, wearable devices, and soft robotics. The stretchable electrode is an integral unit of stretchable systems. Intrinsically conductive polymers such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) can have high mechanical flexibility and good biocompatibility. However, their electrical conductivity and mechanical stretchability should be greatly improved for its applications as the stretchable electrode. Here, we report highly conductive and highly stretchable PEDOT:PSS by incorporating biocompatible d-sorbitol. d-Sorbitol can serve as both the secondary dopant and plasticizer for PEDOT:PSS. It can not only significantly improve the conductivity but also the stretchability. d-Sorbitol-PEDOT:PSS (s-PEDOT:PSS) can have a conductivity of >1000 S/cm, and the conductivity could be maintained at a strain up to 60%. The resistance of s-PEDOT:PSS remains almost constant during repeated stretching-releasing cycles. The mechanism for the stretchability improvement by d-sorbitol is ascribed to the softening of PSSH chains. d-Sorbitol can position among the PSSH chains and thus destructs the hydrogen bonds among the PSSH chains. This makes the conformational change of the PSSH chains under stress become easy and thus increases the mechanical flexibility of PEDOT:PSS. This conductivity is the highest for biocompatible intrinsically conductive polymers with high stretchability.

Transformation of corncob into furfural by a bifunctional solid acid catalyst

A transformation route was developed for the conversion of raw corncob into furfural by a Clbearing solid acid catalyst (HSCSO₃H) prepared by the hydrothermal carbonization and sulfonation of sucralose. The catalytic performances of HSCSO₃H in selected solvents were demonstrated and optimized, where a furfural yield of 90.8 mol% (20.9 wt%) was achieved at 448 K in 30 min in γ-valerolactone/water system. Interestingly, significant furfural yields were also obtained from cellulose. The effect of elevated temperature on furfural yield from high initial feedstock loading was also investigated. HSCSO₃H with COOH, phenolicOH, and Cl as binding sites and SO₃H as the catalytic site on its surface presents a bifunctional catalyst, and synergic effects of these functional groups, reaction solvent property and temperature are made responsible for the good catalytic performances. The catalytic strategy proposed in this study demonstrated an effective transformation of corncob into furfural with a high yield.

Chemocatalytic Conversion of Cellulose into Key Platform Chemicals

Chemocatalytic transformation of lignocellulosic biomass to value-added chemicals has attracted global interest in order to build up sustainable societies. Cellulose, the first most abundant constituent of lignocellulosic biomass, has received extensive attention for its comprehensive utilization of resource, such as its catalytic conversion into high value-added chemicals and fuels (e.g., HMF, DMF, and isosorbide). However, the low reactivity of cellulose has prevented its use in chemical industry due to stable chemical structure and poor solubility in common solvents over the cellulose. Recently, homogeneous or heterogeneous catalysis for the conversion of cellulose has been expected to overcome this issue, because various types of pretreatment and homogeneous or heterogeneous catalysts can be designed and applied in a wide range of reaction conditions. In this review, we show the present situation and perspective of homogeneous or heterogeneous catalysis for the direct conversion of cellulose into useful platform chemicals.

Microwaves in the Catalytic Valorisation of Biomass Derivatives

The application of microwave irradiation in the transformation of biomass has been receiving particular interest in recent years due to the use of polar media in such processes and it is now well-known that for biomass conversion, and particularly for lignocellulose hydrolysis, microwave irradiation can dramatically increase reaction rates with no negative consequences on product selectivity. However, it is only in the last ten years that the utilisation of microwaves has been coupled with catalysis aiming towards valorising biomass components or their derivatives via a range of reactions where high selectivity is required in addition to enhanced conversions. The reduced reaction times and superior yields are particularly attractive as they might facilitate the transition towards flow reactors and intensified production. As a consequence, several reports now describe the catalytic transformation of biomass derivatives via hydrogenation, oxidation, dehydration, esterification and transesterification using microwaves. Clearly, this technology has a huge potential for biomass conversion towards chemicals and fuels and will be an important tool within the biorefinery toolkit. The aim of this chapter is to give the reader an overview of the exciting scientific work carried out to date where microwave reactors and catalysis are combined in the transformation of biomass and its derivatives to higher value molecules and products.

One-step fabrication of carbonaceous solid acid derived from lignosulfonate for the synthesis of biobased furan derivatives

An eco-friendly and low-cost lignosulfonate-based acidic carbonaceous catalyst (LS-SO₃H) was effectively fabricated using the sulfite pulping by-product of sodium lignosulfonate as a precursor by facile one-step simultaneous carbonization and sulfonation, and employed for the synthesis of promising biofuel furan derivatives from biorenewable feedstocks. The catalyst preparation conditions significantly affected the preparation and properties of LS-SO₃H. A relatively high catalyst preparation yield (40.4%) with strong –SO₃H density (1.33 mmol g⁻¹) were achieved when the lignosulfonate was treated in concentrated H₂SO₄ solution at 120 °C for 6 h. The preparation yield of LS-SO₃H was nearly twice as much as that of one-step prepared catalyst using alkaline lignin (another technical lignin from pulping) as a precursor. The as-prepared LS-SO₃H had similar textural characteristics to the frequently-used two-step prepared carbonaceous catalyst involving pyrolysis carbonization and sulfonation. LS-SO₃H was found to show good catalytic activity for the synthesis of 5-ethoxymethylfurfural (EMF) in ethanol medium, affording around 86%, 57% and 47% yields from 5-hydroxymethylfurfural (HMF), fructose and inulin, respectively. Also, a high HMF yield of 83% could be obtained from fructose when DMSO was replaced as reaction medium. The used LS-SO₃H was readily recovered by filtration, and remained active in recycle runs.

An easy-prepared and bio-supported lignosulfonate-based acidic carbonaceous catalyst was developed for the synthesis of promising furan biofuels from biorenewable feedstocks.

Design, synthesis and thermal behaviour of a series of well-defined clickable and triggerable sulfonate polymers

In the printing industry, the exploitation of triggerable materials that can have their surface properties altered on application of a post-deposition external stimulus has been crucial for the production of robust layers and patterns.

Feasibility tests of –SO3H/–SO3−-functionalized magnesium phyllosilicate [–SO3H/–SO3− MP] for environmental and bioenergy applications

We developed water-solubilized and anionic magnesium phyllosilicate [–SO₃H/–SO₃⁻ MP] with pH ∼ 2.0, enabling applications in both environmental engineering and bioenergy.

Facile synthesis of highly efficient and recyclable magnetic solid acid from biomass waste

In this work, sawdust, a biomass waste, is converted into a magnetic porous carbonaceous (MPC) solid acid catalyst by an integrated fast pyrolysis–sulfonation process. The resultant magnetic solid acid has a porous structure with high surface area of 296.4 m² g⁻¹, which can be attributed to the catalytic effect of Fe. The catalytic activity and recyclability of the solid acid catalyst are evaluated during three typical acid-catalyzed reactions: esterification, dehydration, and hydrolysis. The favorable catalytic performance in all three reactions is attributed to the acid's high strength with 2.57 mmol g⁻¹ of total acid sites. Moreover, the solid acid can be reused five times without a noticeable decrease in catalytic activity, indicating the stability of the porous carbon (PC)–sulfonic acid group structure. The findings in the present work offer effective alternatives for environmentally friendly utilization of abundant biomass waste.

Direct conversion of chitin biomass to 5-hydroxymethylfurfural in concentrated ZnCl2 aqueous solution

The direct conversion of chitin biomass to 5-hydroxymethylfurfural (5-HMF) in ZnCl2 aqueous solution was studied systemically. D-Glucosamine (GlcNH2) was chosen as the model compound to investigate the reaction, and 5-HMF could be obtained in 21.9% yield with 99% conversion of GlcNH2. Optimization of the reaction parameters including the screening of 8 co-catalysts was carried out. Among them, AlCl3 and B(OH)3 improved 5-HMF yield, whereas CdCl2, CuCl2 and NH4Cl had no effect. CrCl3, SnCl4 and SnCl2 showed negative effects, i.e. lower yields. Consequently, the optimal reaction conditions were found to be 67 wt.% ZnCl2 aqueous solution, at 120 °C without co-catalyst. The reactions were further studied by in situ NMR, and no intermediate or other byproducts, except humins, were observed. Finally, the substrate scope was expanded from GlcNH2 to N-acetyl-D-glucosamine and various chitosan polymers with different molecular weights, 5-HMF yield from polymers were generally lower than that from GlcNH2.