Chitin microsphere supported Pd nanoparticles as an efficient and recoverable catalyst for CO oxidation and Heck coupling reaction

Seafood waste derived Pt/Chitin nanocatalyst for efficient hydrogenation of nitroaromatic compounds

The fabrication of reliable, reusable and efficient catalyst is crucial for the conversion of nitroaromatic compounds into more chemically valuable amine-based molecules. In this study, a series of chitin supported platinum (Pt) catalysts with high catalytic activity, stability, and reusability were developed by using chitin derived from seafood waste as raw materials. The catalytic performance differences among these catalysts activated by different methods were investigated by hydrogenation of nitroaromatic compounds. The results showed that the multilayer hierarchical pore structure and abundance of hydroxyl and acetamido groups in chitin provided ample anchoring sites for Pt nanoparticles (NPs), ensuring the high dispersion of Pt NPs. Moreover, the interconnected channels between chitin nanofibrous microspheres facilitated rapid transport of reaction substrates. The best Pt/Chitin catalyst exhibited excellent catalytic activity and broad substrate applicability in hydrogenation of nitroaromatic compounds. Significantly, even after 20 runs, no discernible deactivation of activity was observed, demonstrating exceptional catalytic reusability. The application of seafood waste-based catalysts is conducive to the development of a green/sustainable society.

Chitin microspheres: From fabrication to applications

Chitin microspheres (CMs) have attracted increasing attention due to their biocompatibility, uniform size and shape, large surface area, and porous structure. Considerable research efforts have been focused on developing CMs and promoting their applications in various areas. In this context, this review aims to describe the most recent progress in the fabrication and application of CMs. Different routes that can be used to prepare CMs, such as the drip method and the emulsion method, are emphatically introduced. Moreover, the applications of CMs as drug delivery systems, wound dressings, three-dimensional (3D) scaffolds, water purification, and functional supporting materials in the fields of biomedicine, tissue engineering, environmental protection, and energy storage are also highlighted. We hope this review can provide a comprehensive and useful database for further innovation of CMs.

Supramolecular chitin-based hydrogels with self-adapting and fast-degradation properties for enhancing wound healing

Due to the features of high porosity, high water content, and tunable viscoelasticity, hydrogels have attracted numerous attentions in the promotion of wound closure. However, the lack of abilities to adapt the wounds of complex shapes and prevent postoperative adhesion limits their therapeutic outcomes in wound healing. To address the above challenges, the supramolecular chitin-based (SMCT) hydrogels are created via the host-guest pre-assembly strategy of β-cyclodextrin (βCD) and adamantane (Ad). The reversible host-guest crosslinks endow the SMCT hydrogels with highly dynamic networks, which can better accommodate irregularly shaped wounds compared with the covalent chitin-based hydrogels with similar mechanical properties. In addition, the SMCT hydrogels show rapid in vivo degradability (degradation time ≈ 2 days) due to the enzyme-triggered degradability of chitin, which do not need to be removed from the wounds after service and thus avoid the secondary damage to skin during dressing change. Owing to the hydrophobic cavity of βCD, the SMCT hydrogels can facilitate the load and release of curcumin with anti-inflammatory, antibacterial, and antioxidative activities, thereby significantly improving the wound healing efficiency. This work provides valuable guidance to the design of self-adaptive and fast-degradable hydrogels that hold great potential for enhancing the wound healing in skin and other tissues.

Chitosan derived efficient and stable Pd nano-catalyst for high efficiency hydrogenation

The design and development of green and efficient supported catalysts is the frontier direction in the field of green synthesis, which conforms to the strategic concept of green sustainable chemistry and "carbon neutrality". Herein, we used a renewable resource chitosan (CS) derived from seafood wastes of chitin as carriers to design two different chitosan-supported palladium (Pd) nano-catalysts through different activation methods. The Pd particles were firmly and uniformly dispersed on the chitosan microspheres due to the interconnected nanoporous structure and functional groups of chitosan, proved by diverse characterizations. The chitosan supported catalysts (Pd@CS) was applied to hydrogenation of 4-nitrophenol, which showed competitive catalytic activity compared to commercial Pd/C, un-supported nano-Pd and Pd(OAc)₂ catalysts, as well as excellent catalytic activity, good reusability, long-life and broad applicability in selective hydrogenation of aromatic aldehydes, suggesting potential of applications in green industrial catalysis.

Pd nanoparticles decorated on Schiff base-modified chitosan/CeO2 as a heterogeneous and retriable nanocatalyst for Heck reactions and remediation of environmental pollutants

In this paper, we have developed a novel, highly active, eco-friendly, and versatile heterogeneous catalyst system in which Pd nanoparticles are decorated on Schiff base-modified chitosan‑cerium oxide particles (Pd@CS-CeO₂). In order to confirm the successful fabrication of Pd@CS-CeO₂, FTIR, XRD, SEM, TEM, BET, TG/DTG, and EDS analyses were performed, and its performance was evaluated as a heterogeneous nanocatalyst in Heck coupling reaction and reduction of nitro compounds. The catalytic tests showed that the desired Heck products were readily produced by Pd@CS-CeO₂ without being contaminated with the aryl iodides, bromides, and chlorides. Moreover, different nitro compounds were efficiently reduced to corresponding amino compounds by Pd@CS-CeO₂ within 95-160 s. Thanks to the heterogeneous nature of Pd@CS-CeO₂ catalyst, it was easily recovered via simple filtration and reused up to 5 successive runs by giving 88 % yield. Due to its good catalytic and reusability performance together with stability/durability, Pd@CS-CeO₂ is promising candidate as a catalyst for various catalytic or organic reactions.

Contributions of Women in Recent Research on Biopolymer Science

Nowadays, biopolymers are playing a fundamental role in our society because of the environmental issues and concerns associated with synthetic polymers. The aim of this Special Issue entitled ‘Women in Polymer Science and Technology: Biopolymers’ is highlighting the work designed and developed by women on biopolymer science and technology. In this context, this short review aims to provide an introduction to this Special Issue by highlighting some recent contributions of women around the world on the particular topic of biopolymer science and technology during the last 20 years. In the first place, it highlights a selection of important works performed on a number of well-studied natural polymers, namely, agar, chitin, chitosan, cellulose, and collagen. Secondly, it gives an insight into the discovery of new polysaccharides and enzymes that have a role in their synthesis and in their degradation. These contributions will be paving the way for the next generation of female and male scientists on this topic.

Cellulose derived Pd nano-catalyst for efficient catalysis

We report a C–Pd catalyst derived from a renewable cellulose resource that exhibited excellent catalytic activity and reusability in the Suzuki–Miyaura coupling reaction.

Progresses in chitin, chitosan, starch, cellulose, pectin, alginate, gelatin and gum based (nano)catalysts for the Heck coupling reactions: A review

Heck cross-coupling reaction (HCR) is one of the few transition metal catalyzed CC bond-forming reactions, which has been considered as the most effective, direct, and atom economical synthetic method using various catalytic systems. Heck reaction is widely employed in numerous syntheses including preparation of pharmaceutical and biologically active compounds, agrochemicals, natural products, fine chemicals, etc. Commonly, Pd-based catalysts have been used in HCR. In recent decades, the application of biopolymers as natural and effective supports has received attention due to their being cost effective, abundance, and non-toxicity. In fact, recent studies demonstrated that biopolymer-based catalysts had high sorption capacities, chelating activities, versatility, and stability, which make them potentially applicable as green materials (supports) in HCR. These catalytic systems present high stability and recyclability after several cycles of reaction. This review aims at providing an overview of the current progresses made towards the application of various polysaccharide and gelatin-supported metal catalysts in HCR in recent years. Natural polymers such as starch, gum, pectin, chitin, chitosan, cellulose, alginate and gelatin have been used as natural supports for metal-based catalysts in HCR. Diverse aspects of the reactions, different methods of preparation and application of polysaccharide and gelatin-based catalysts and their reusability have been reviewed.

Palladium nanoparticles in situ synthesized on Cyclea barbata pectin as a heterogeneous catalyst for Heck coupling in water, the reduction of nitrophenols and alkynes

This study develops an effective method for in situ synthesis of PdNPs using Cyclea barbata pectin as green reducing and stabilizing reagent. The catalytic activity of nanocomposite was evaluated for Heck coupling reaction, reduction of nitrophenols and reduction of alkynes.

Palladium nanoparticles supported on chitin-based nanomaterials as heterogeneous catalysts for the Heck coupling reaction

In this report, chitin and chitosan nanocrystals were used as biomass-based supports for Pd nanoparticles (NPs) used as a heterogeneous catalyst for the Heck coupling reaction. By using a one-pot fabrication method, a Pd salt precursor was directly reduced and deposited onto these nanocrystal catalysts. Characterization of these nanocomposites showed disperse Pd NPs on the surfaces of the chitinous nanocrystals. Heck coupling model reactions revealed full product yield in relatively benign conditions, outcompeting the use of other catalysts supported on biomass-based nanomaterials, including cellulose nanocrystals. These initial results show the potential for using chitinous nanomaterials as effective catalyst supports in cross-coupling reactions.