Carboxymethylcellulose-Supported Palladium Nanoparticles Generated in Situ from Palladium(II) Carboxymethylcellulose: An Efficient and Reusable Catalyst for Suzuki–Miyaura and Mizoroki–Heck Reactions

Use of carboxymethyl cellulose as binder for the production of water-soluble catalysts

Bio-based polymers are materials of high interest given the harmful environmental impact that involves the use of non-biodegradable fossil products for industrial applications. These materials are also particularly interesting as bio-based ligands for the preparation of metal nanoparticles (MNPs), employed as catalysts for the synthesis of high value chemicals. In the present study, Ru (0) and Rh(0) Metal Nanoparticles supported on Sodium Carboxymethyl cellulose (MNP(0)s-CMCNa) were prepared by simply mixing RhCl3x3H2O or RuCl3 with an aqueous solution of CMCNa, followed by NaBH4 reduction. The formation of MNP(0)s-CMCNa was confirmed by FT-IR and XRD, and their size estimated to be around 1.5 and 2.2 nm by TEM analysis. MNP(0)s-CMCNa were employed for the hydrogenation of (E)-cinnamic aldehyde, furfural and levulinic acid. Hydrogenation experiments revealed that CMCNa is an excellent ligand for the stabilization of Rh(0) and Ru(0) nanoparticles allowing to obtain high conversions (>90 %) and selectivities (>98 %) with all substrates tested. Easy recovery by liquid/liquid extraction allowed to separate the catalyst from the reaction products, and recycling experiments demonstrated that MNPs-CS were highly efficiency up to three times in best hydrogenation conditions.

Chitosan as a Bio-Based Ligand for the Production of Hydrogenation Catalysts

Bio-based polymers are attracting increasing interest as alternatives to harmful and environmentally concerning non-biodegradable fossil-based products. In particular, bio-based polymers may be employed as ligands for the preparation of metal nanoparticles (M(0)NPs). In this study, chitosan (CS) was used for the stabilization of Ru(0) and Rh(0) metal nanoparticles (MNPs), prepared by simply mixing RhCl3 × 3H2O or RuCl3 with an aqueous solution of CS, followed by NaBH4 reduction. The formation of M(0)NPs-CS was confirmed by Fourier Transform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC), Thermal Gravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Analysis (EDX), Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). Their size was estimated to be below 40 nm for Rh(0)-CS and 10nm for Ru(0)-CS by SEM analysis. M(0)NPs-CS were employed for the hydrogenation of (E)-cinnamic aldehyde and levulinic acid. Easy recovery by liquid-liquid extraction made it possible to separate the catalyst from the reaction products. Recycling experiments demonstrated that M(0)NPs-CS were highly efficient up to four times in the best hydrogenation conditions. The data found in this study show that CS is an excellent ligand for the stabilization of Rh(0) and Ru(0) nanoparticles, allowing the production of some of the most efficient, selective and recyclable hydrogenation catalysts known in the literature.

Lignin-functionalized cobalt for catalytic reductive degradation of organic dyes in simple and hybrid binary systems

To fulfill the unprecedented valorization approaches for lignocellulose, this work focuses on the potential of lignin-derived catalytic systems for bio-remediation, which are natural materials perceived to address the increased demand for eco-conscious catalyzed processes. A useful lignin-functionalized cobalt (Lig-Co) catalyst has been prepared, well-characterized and deployed for the catalyzed reducing decomposition of stable harmful organic pollutants such as methylene blue (MB) and methyl orange (MO), in simple and binary systems. The multifunctional character of lignin and the presence of various active sites can promote effectively loaded metal nanoparticles (NPs). Considerably, optimizing detoxification tests showed that the uncatalyzed use of NaBH4 as a reductive agent led to an incomplete reduction of organic contaminants over a long period of up to 65 min. Interestingly, Lig-Co catalyst exhibited a high reduction rate and turnover frequency of up to 99.23% and 24.12 min-1 for MB, respectively, while they reached 99.25% and 26.21 min-1 for MO at normal temperature. Kinetically quick catalytic reaction was also demonstrated for the hybrid system, in which the rate constant k was 0.175 s-1 and 0.165 s-1 for MB and MO, respectively, within a distinctly low reaction time of around 120 s. The reproducibility of the Lig-Co catalyst induces a desirable capacity to reduce stable dyes present simultaneously in the binary system, with 6 successive catalytic runs and over 80% of activity retained. Such robust findings underline the considerable interest in developing future lignin-mediated catalytic transformations and upscaling biomass-derived products, to meet the growing demand for sustainable and eco-friendly alternatives in various industries.

Pd@HKUST-1@Cu(II)/CMC composite bead as an efficient synergistic bimetallic catalyst for Sonogashira cross-coupling reactions

We fabricated an efficient Pd@HKUST-1@Cu(II)/CMC composite bead catalyst through an innovative strategy based on the unique properties of metal-organic frameworks (MOFs) and carboxymethylcellulose (CMC). In this strategy, HKUST-1 MOFs were grown in-situ on the surface of micrometer-sized Cu-based CMC beads (Cu(II)/CMC), then Pd(II) ions were incorporated into the pores of the MOF and further be partially reduced to Pd(0) NPs, which is an active species for oxidative addition with aryl halides in Sonogashira reactions. The micron-sized Cu(II)/CMC beads were formed through inter/intramolecularly crosslinking facilitated by Cu(II) ions, which was achieved by the metathesis of Cu(II) with numerous carboxylic groups of CMC. Such Cu(II)/CMC bead offers many Cu(II) ions as interaction sites for in-situ nucleation and growth of HKUST-1 MOFs. The architecture and composition of the prepared Pd@HKUST-1@Cu(II)/CMC composite were fully verified by various techniques such as FTIR, XRD, TGA, BET, XPS, SEM, TEM, EDX, and elemental mapping analysis. This novel composite bead was applied as an efficient and reusable heterogeneous Pd/Cu bimetallic catalyst for Sonogashira reactions, decarbonylative Sonogashira reaction, and Sonogashira cyclization tandem reactions. The catalyst is readily isolated by simple filtration, and can be reused for five consecutive runs with retaining its activity and structural integrity.

Pd nanoparticles embedded in nanolignin (Pd@LNP) as a water dispersible catalytic nanoreactor for Cr(VI), 4-nitrophenol reduction and CC coupling reactions

The use of water-dispersible and sustainable Pd nanocatalysts to reduce toxic heavy metal ions and catalyze important organic reactions has profound significance for the environmental remediation and the catalytic industry. In this work, a novel water-dispersible and recyclable Pd@LNPs nanoreactor composed of Pd nanoparticle cluster core and LNPs shell was developed in microwave reactor in aqueous solution. It turned out that Pd nanoparticles grew uniformly and stably inside LNPs nanosphere due to the coordinated binding and interaction between Pd and the functional groups in LNPs, which was significantly different from surface loading. The green and biodegradable LNPs nanospheres are not only used as reducing agents for Pd (II) and nanocarriers, but also act as individual nanocontainers to provide favorable sites for reactions and effectively control the entry and release of reactants and products. Furthermore, the excellent and efficient catalytic properties of Pd@LNPs were exhibited by CC coupling reactions and the reduction of Cr(VI) and 4-nitrophenol. The Pd@LNPs prepared in this study have the advantages of excellent dispersion, great recyclability, high turnover frequency and better green sustainability metrics. It will have a great significance for the development of the potential high-value of lignin and the progress in the field of bio-nanocatalysts.

Carboxymethyl cellulose nanocolloids anchored Pd(0) nanoparticles (CMC@Pd NPs): synthesis, characterization, and catalytic application in transfer hydrogenation

Herein, we report on the preparation of novel colloidal system based on carboxymethyl cellulose (CMC) and Pd nanoparticles (CMC@Pd NPs) via an ecofriendly auto-reduction process under mild conditions. In the first step, the follow-up of reduction and preparation of CMC anchored palladium nanoparticles (Pd NPs) in aqueous solution was carried out using UV-Vis spectroscopy. Thereafter, the monodispersed colloids were fully characterized by advanced analytical, structural, and morphological techniques. Based on Scherrer equation, the as-synthesized CMC@Pd NPs crystallite size was about 10.88 nm. Accordingly, the detailed microscopic study revealed CMC nanocolloids anchored uniform distribution of Pd NPs and the presence of CMC nanofilm as protective monolayer. To the best of our knowledge, the observed nanoscale properties are reported for the first time for CMC-M system. The performance of the as-synthesized CMC@Pd nanocolloids was first investigated in the reduction of 4-nitrophenol, as a model substrate, to 4-aminophenol using NaBH4 as a hydrogen source. Moreover, the catalytic reduction of various nitroarenes bearing electron withdrawing or donating substituents was carried out and monitored by UV-Vis spectroscopy. The chemo- and regioselectivity of the catalytic reduction in presence of CMC@Pd NPs were also studied. Consequently, the prepared CMC@Pd nanocolloids exhibit remarkable activity, good heterogeneity, and higher reusability and stability for the catalytic reduction reaction under mild conditions.

Aqueous micellar technology: an alternative beyond organic solvents

Solvents are the major source of chemical waste from synthetic chemistry labs. Growing attention to more environmentally friendly sustainable processes demands novel technologies to substitute toxic or hazardous solvents. If not always, sometimes, water can be a suitable substitute for organic solvents, if used appropriately. However, the sole use of water as a solvent remains non-practical due to its incompatibility with organic reagents. Nonetheless, over the past few years, new additives have been disclosed to achieve chemistry in water that also include aqueous micelles as nanoreactors. Although one cannot claim micellar catalysis to be a greener technology for every single transformation, it remains the sustainable or greener alternative for many reactions. Literature precedents support that micellar technology has much more potential than just as a reaction medium, i.e., the role of the amphiphile as a ligand obviating phosphine ligands in catalysis, the shielding effect of micelles to protect water-sensitive reaction intermediates in catalysis, and the compartmentalization effect. While compiling the powerful impact of micellar catalysis, this article highlights two diverse recent technologies: (i) the design and employment of the surfactant PS-750-M in selective catalysis; (ii) the use of the semisynthetic HPMC polymer to enable ultrafast reactions in water.

Spray-Assisted Interfacial Polymerization to Form CuII/I@CMC-PANI Film: An Efficient Dip Catalyst for A3 Reaction

A novel and interesting method for the preparation of carboxymethylcellulose–polyaniline film-supported copper catalyst (Cu^II/I@CMC-PANI) has been developed via spray-assisted interfacial polymerization. Using copper sulfate as an initiator, spraying technology was introduced to form a unique interface that is perfectly beneficial to the polymerization of aniline monomers onto carboxymethylcellulose macromolecule chains. To further confirm the composition and structure of the as-prepared hybrid film, it was systematically characterized by inductively coupled plasma (ICP), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and thermogravimetric analysis (TGA) techniques. The Cu content in the fresh Cu^II/I@CMC-PANI film was determined to be 1.805 mmol/g, and spherical nanoparticles with an average size of ca. 10.04 nm could be observed in the hybrid film. The Cu^II/I@CMC-PANI hybrid film was exerted as a dip catalyst to catalyze the aldehyde–alkyne–amine (A³) coupling reactions. High yields of the products (up to 97%) were obtained in this catalytic system, and the catalyst could be easily picked up from the reaction mixture by tweezers and reused for at least six consecutive runs, without any discernible losses in its activity in the model reaction. The dip catalyst of Cu^II/I@CMC-PANI, with easy fabrication, convenient deployment, superior catalytic activity, and great reusability, is expected to be very useful in organic synthesis.

Wood-Sourced Polymers as Support for Catalysis by Group 10 Transition Metals

Despite providing interesting solutions to reduce the number of synthetic steps, to decrease energy consumption or to generate less waste, therefore contributing to a more sustainable way of producing important chemicals, the expansion of the use of homogeneous catalysis in industrial processes is hampered by several drawbacks. One of the most important is the difficulty to recycle the noble metals generating potential high costs and pollution of the synthesized products by metal traces detrimental to their applications. Supporting the metals on abundant and cheap biosourced polymers has recently appeared as an almost ideal solution: They are much easier to recover from the reaction medium and usually maintain high catalytic activity. The present bibliographical review focuses on the development of catalysts based on group 10 transition metals (nickel, palladium, platinum) supported on biopolymers obtained from wood, such as cellulose, hemicellulose, lignin, and their derivatives. The applications of these catalysts in organic synthesis or depollution are also addressed in this review with examples of C-C couplings, oxidation, or hydrogenation reactions.

Preparation of Carboxymethyl Cellulose-g- Poly(acrylamide)/Attapulgite Porous Monolith With an Eco-Friendly Pickering-MIPE Template for Ce(III) and Gd(III) Adsorption

Due to their high specific surface and metal-binding functional groups in their crosslinked polymeric networks, monolithic materials incorporating a porous structure have been considered one of the most efficient kinds of adsorbents for rare earth element recovery. Herein, a facile and novel monolithic multi-porous carboxymethyl cellulose-g-poly(acrylamide)/attapulgite was synthesized by free radical polymerization via green vegetable oil-in-water Pickering medium internal phase emulsion (O/W Pickering-MIPEs), which was synergically stabilized by attapulgite and tween-20. The homogenizer rotation speed and time were investigated to form stable Pickering-MIPEs. The effects of different types of oil phase on the formation of Pickering-MIPEs were investigated with stability tests and rheological characterization. The structure and composition of the porous material when prepared with eight kinds of vegetable oil were characterized by FTIR and SEM. The results indicate that the obtained materials, which have abundant interconnected porosity, are comparable to those fabricated with Pickering-HIPE templates. The adsorption experiment demonstrated that the prepared materials have a fast capture rate and high adsorption capacities for Ce(III) and Gd(III), respectively. The saturation adsorption capacities for Ce(III) and Gd(III) are 205.48 and 216.73 mg/g, respectively, which can be reached within 30 min. Moreover, the monolithic materials exhibit excellent regeneration ability and reusability. This work provides a feasible and eco-friendly pathway for the construction of a multi-porous adsorbent for adsorption and separation applications.

Chemoselective and Continuous Flow Hydrogenations in Thin Films Using a Palladium Nanoparticle Catalyst Embedded in Cellulose Paper

Cellulose immobilized palladium (0) nanoparticles (PdNPs) were prepared for the use in scalable catalytic reactions in flow. Preparation of the catalyst is remarkably simple and fast, where a palladium acetate solution is drop-casted onto cellulose paper and then exposed to 1 atm of hydrogen for a mere 90 s to produce embedded Pd(0) nanoparticles. This catalyst system is efficient in the hydrogenation of alkenes, nitroarenes, ketones, and enamides, with products formed in high yields, under ambient pressure and temperature. The system is also effective for transfer hydrogenation using ammonium formate as an alternative hydrogen source. A high catalyst stability and reusability are demonstrated along with the chemoselective and scalable synthesis of industrially important fine chemicals, including the biobased molecule cyrene.

Easily fabricated and recyclable Pd&Cu@Al catalyst for gram-scale phosphine-free Heck reactions with high TON

A unique Pd&Cu@Al catalyst was easily fabricated just by immersing commercial aluminum foil in a mixed xylene solution of PdCl₂ and CuCl₂. The catalyst fabrication process led to aluminum oxide coatings in situ, which supported the metal nanoparticles and enhanced their catalytic activities for the phosphine-free Heck reaction of aryl halides and styrenes with high turnover number (TON) up to 3.9×10⁵. The reaction can be scaled up to at least 100mmol and has been applied in modification of drug Lapatinib's intermediate with low metal residue. This novel catalyst is of good application potential in industrial production because it was extremely easy to be recycled, in regardless of the generation of the insoluble impurities or tars during the reaction processes.

Fabrication of CMC-g-PAM Superporous Polymer Monoliths via Eco-Friendly Pickering-MIPEs for Superior Adsorption of Methyl Violet and Methylene Blue

A series of superporous carboxymethylcellulose-graft-poly(acrylamide)/palygorskite (CMC-g-PAM/Pal) polymer monoliths presenting interconnected pore structure and excellent adsorption properties were prepared by one-step free-radical grafting polymerization reaction of CMC and acrylamide (AM) in the oil-in-water (O/W) Pickering-medium internal phase emulsions (Pickering-MIPEs) composed of non-toxic edible oil as a dispersion phase and natural Pal nanorods as stabilizers. The effects of Pal dosage, AM dosage, and co-surfactant Tween-20 (T-20) on the pore structures of the monoliths were studied. It was revealed that the well-defined pores were formed when the dosages of Pal and T-20 are 9–14 and 3%, respectively. The porous monolith can rapidly adsorb 1,585 mg/g of methyl violet (MV) and 1,625 mg/g of methylene blue (MB). After the monolith was regenerated by adsorption-desorption process for five times, the adsorption capacities still reached 92.1% (for MV) and 93.5% (for MB) of the initial maximum adsorption capacities. The adsorption process was fitted with Langmuir adsorption isotherm model and pseudo-second-order adsorption kinetic model very well, which indicate that mono-layer chemical adsorption mainly contribute to the high-capacity adsorption for dyes. The superporous polymer monolith prepared from eco-friendly Pickering-MIPEs shows good adsorption capacity and fast adsorption rate, which is potential adsorbent for the decontamination of dye-containing wastewater.

Pd(0)-CMC@Ce(OH)(4) organic/inorganic hybrid as highly active catalyst for the Suzuki-Miyaura reaction

A very easy sequential metathesis for the synthesis of Pd(II)-CMC@Ce(OH)₄ organic/inorganic hybrid and its application as effective pre-catalyst for the Suzuki-Miyaura reaction have been reported. It was found that the Pd nanoparticles (Pd NPs) were formed in situ in the course of the Suzuki-Miyaura couplings when Pd(II)-CMC@Ce(OH)₄ was used as a pre-catalyst. The activity of the Pd NPs in the reaction was enhanced synergistically by the unique redox properties (Ce³⁺/Ce⁴⁺) of Ce(OH)₄ and coordination with carboxyl groups as well as free hydroxyl groups of the hybrid of CMC@Ce(OH)₄. The results exhibit the Pd(0)-CMC@Ce(OH)₄ is super over Pd(II)@CMC, Pd(II)@CeO₂, and Pd(II)@Ce(OH)₄ catalysts in the Suzuki-Miyaura reaction. Moreover, the catalyst could be easily separated by simple filtration and reused at least seven runs without losing its activity.

Self-assembled nanoparticles based on a carboxymethylcellulose–ursolic acid conjugate for anticancer combination therapy

A new self-assembled nanoparticle platform based on a carboxymethylcellulose (CMC)–ursolic acid (UA) conjugate is presented for the first time.

Nickel nanoparticles-chitosan composite coated cellulose filter paper: An efficient and easily recoverable dip-catalyst for pollutants degradation

In this report, we used cellulose filter paper (FP) as high surface area catalyst supporting green substrate for the synthesis of nickel (Ni) nanoparticles in thin chitosan (CS) coating layer and their easy separation was demonstrated for next use. In this work, FP was coated with a 1 wt% CS solution onto cellulose FP to prepare CS-FP as an economical and environment friendly host material. CS-FP was put into 0.2 M NiCl₂ aqueous solution for the adsorption of Ni²⁺ ions by CS coating layer. The Ni²⁺ adsorbed CS-FP was treated with 0.1 M NaBH₄ aqueous solution to convert the ions into nanoparticles. Thus, we achieved Ni nanoparticles-CS composite through water based in-situ preparation process. Successful Ni nanoparticles formations was assessed by FESEM and EDX analyses. FTIR used to track the interactions between nanoparticles and host material. Furthermore, we demonstrated that the nanocomposite displays an excellent catalytic activity and reusability in three reduction reactions of toxic compounds i.e. conversion of 4-nitrophenol to 4-aminophenol, 2-nitrophenol to 2-aminophenol, and methyl orange dye reduction by NaBH₄. Such a fabrication process of Ni/CS-FP may be applicable for the immobilization of other metal nanoparticles onto FP for various applications in catalysis, sensing, and environmental sciences.

Copper(ii) carboxymethylcellulose (CMC-CuII) as an efficient catalyst for aldehyde–alkyne–amine coupling under solvent-free conditions

A novel heterogeneous Cu(ii) carboxymethylcellulose catalyst was prepared and successfully employed in the A3 coupling without using any co-catalyst, other additives, bases under solvent-free conditions.