## 1 Introduction  
In recent decades, the scientific world has developed a clear understanding of the future of the development of the chemical and fuel industries, in which an important place will be occupied by platform chemicals synthesized from biomass [1], primarily from lignocellulosic produced from forestry and agriculture waste, the volume of which reaches 200 billion tons per year [2]. In 2004 the US Department of Energy compiled a list of biomass-derived chemicals with the highest added value. These include the following: 1,4-diacids (succinic, fumaric, malic acids), 2,5-furandicarboxylic acid, 3-hydroxypropionic acid, aspartic acid, glucaric acid, glutamic acid, itaconic acid, levulinic acid, 3-hydroxybutyrolactone, and glycerol, as well as sugar alcohols (sorbitol, xylitol, etc.) [3]. This list was updated in 2010 [4], when ethanol, furfural, 5-hydroxymethylfurfural, isoprene, and lactic acid were added. All these substances underlie many sequences of chemical transformations aimed at the synthesis of polymers [5], biofuels [6], and raw materials for the chemical industry [7]. The volume of platform chemicals derived from biomass is constantly growing and today already represents hundreds of billions of US dollars annually [8], which in mass terms approaches approximately 100 million tons per year [9; 10]. Various large chemical companies, such as DuPont, BASF AG, Dow Chemical, and many others are developing technologies for the conversion of biomass into platform chemicals and their integration into existing processes [8]. The current energy crisis is also a driving force for the market growth of commercially valuable biomass-derived chemicals and is expected to increase by 16% in 2025 [11], which in monetary terms should reach 867.7 billion US dollars [12]. The most attractive biomass is lignocellulosic, since it does not provide any nutritional value [13]. To ensure the sustainable processing of biomass, it is necessary to address fundamental economic, social, and environmental requirements. For example, none of the strategies for the pretreatment of lignocellulosic biomass have proven to be environmentally friendly and safe [14]. The strong structure of microcrystalline cellulose makes it difficult to involve plant biomass directly in conversion processes. The dissolution and destruction of cellulose macromolecules requires the use of complex and environmentally harmful solvents (ionic liquids, mineral acids, etc. ), expensive and non-regenerable enzymes, and/or \"harsh\" reaction conditions (high temperatures and pressures) [15]. One effective solution is heterogeneous catalysts designed for a required range of reaction conditions [16]. However, the use of catalysts also brings a number of problems related to their stability under hydrothermal conditions, toxicity, high selectivity to the target products, etc. [17]. In this regard, an urgent task is to develop new catalytic systems that are stable under \"harsh\" conditions of plant biomass conversion, have high activity and yields of target products, and are safe for humans and the environment. Hypercrosslinked polymers are very promising materials, which present many properties of effective heterogeneous catalysts, like developed specific surface area (from hundreds to few thousands of m\({}^{2}\)/g), controlled porosity, possibility of surface functionalization, exceptional adsorption properties [18; 19], chemical and thermal stability, and low cost [20]. In addition, some hypercrosslinked polymers can be synthesized from monomers of biological origin or related compounds [21], for example using lignin, catechol, and starch, which in combination with a mechanochemical method (without any use of toxic chlorine-containing solvents) fully complies with the principles of green chemistry [22; 23]. The carbonizes of hypercrosslinked polymers also look promising for use as catalysts [24]. However, despite the advantages, the use of hypercrosslinked polymers as heterogeneous catalysts is not always straightforward.