Recently, the use of plant-origin materials has become especially important due to the aggravation of environmental problems and the shortage and high cost of synthetic materials. One of the potential candidates among natural organic compounds is polysaccharides, characterized by a number of advantages over synthetic polymers. In recent years, natural polysaccharides have been used to design composite catalysts for various organic syntheses. This review is devoted to the current state of application of polysaccharides (chitosan, starch, pectin, cellulose, and hydroxyethylcellulose) and composites based on their catalysis. The article is divided into four main sections based on the type of polysaccharide: (1) chitosan-based nanocomposites; (2) pectin-based nanocomposites; (3) cellulose (hydroxyethylcellulose)-based nanocomposites; and (4) starch-based nanocomposites. Each section describes and summarizes recent studies on the preparation and application of polysaccharide-containing composites in various chemical transformations. It is shown that by modifying polysaccharides, polymers with special properties can be obtained, thus expanding the range of biocomposites for catalytic applications.

The development of effective bifunctional catalysts demonstrating high performance in both photocatalytic hydrogen evolution and selective hydrogenation of unsaturated compounds is of great interest for photocatalytic transfer hydrogenation. In this work, TiO₂ and Pd@TiO₂ catalysts were studied in two separate processes: photocatalytic H₂ evolution and conventional hydrogenation reactions. Photocatalytic properties of titanium dioxide synthesized by a simple precipitation method were compared with those of commercial ones. Commercial anatase with a lower agglomeration degree showed better activity in H₂ evolution. Further modification of the commercial anatase with Pd resulted in increasing its activity, achieving an H₂ evolution rate of 760 μmol/h g_cat. The Pd catalysts supported on different TiO₂ samples were tested in hydrogenation of acetylenic compounds. The activity of the Pd@TiO₂ catalysts was found to be dependent on the photocatalytic properties of TiO₂ supports. XPS studies of Pd catalysts indicated that commercial anatase with better photocatalytic properties provided easier reduction of Pd²⁺ to active Pd⁰ particles. The Pd catalyst supported on commercial anatase demonstrated the highest activity in the hydrogenation process. The W_C≡C rate achieved 2.6 × 10⁻⁶, 9.0 × 10⁻⁶ and 35.7 × 10⁻⁶ mol/s for hydrogenation of 2-hexyne-1-ol, 5-hexyne-1-ol and 2-hexyne, respectively. The selectivity of the catalyst to target olefinic compounds was 94–96%. In addition, the hydrogenation rate was found to be significantly affected by reaction conditions such as hydrogen concentration and solvent composition. The W_C≡C rate decreased linearly with decreasing hydrogen concentration in a H₂:He gas mixture (30–100 vol%). Performing the reaction in 0.10 M NaOH ethanolic solution resulted in increasing the W_C≡C rate and selectivity of the process. The Pd catalyst was reused in an alkali medium (NaOH in ethanol) for 35 runs without significant degradation in its catalytic activity. Thus, the results obtained in this work can be useful in photocatalytic transfer hydrogenation.

The proposed paper describes a simple and environmentally friendly method for the synthesis of three-component polymer–inorganic composites, which includes the modification of zinc oxide or montmorillonite (MMT) with chitosan (CS), followed by the immobilization of palladium on the resulting two-component composites. The structures and properties of the obtained composites were characterized by physicochemical methods (IRS, TEM, XPS, SEM, EDX, XRD, BET). Pd–CS species covered the surface of inorganic materials through two different mechanisms. The interaction of chitosan polyelectrolyte with zinc oxide led to the deprotonation of its amino groups and deposition on the surface of ZnO. The immobilization of Pd on CS/ZnO occurred by the hydrolysis of [PdCl₄]²⁻, followed by forming PdO particles by interacting with amino groups of chitosan. In the case of CS/MMT, protonated amino groups of CS interacted with negative sites of MMT, forming a positively charged CS/MMT composite. Furthermore, [PdCl₄]²⁻ interacted with the –NH³⁺ sites of CS/MMT through electrostatic force. According to TEM studies of 1%Pd–CS/ZnO, the presence of Pd nanoclusters composed of smaller Pd nanoparticles of 3–4 nm in size were observed on different sites of CS/ZnO. For 1%Pd–CS/MMT, Pd nanoparticles with sizes of 2 nm were evenly distributed on the support surface. The prepared three-component CS–inorganic composites were tested through the hydrogenation of 2-propen-1-ol and acetylene compounds (phenylacetylene, 2-hexyn-1-ol) under mild conditions (T—40 °C, P_H2—1 atm). It was shown that the efficiency of 1%Pd–CS/MMT is higher than that of 1%Pd–CS/ZnO, which can be explained by the formation of smaller Pd particles that are evenly distributed on the support surface. The mechanism of 2-hexyn-1-ol hydrogenation over an optimal 1%Pd–CS/MMT catalyst was proposed.