## 1 Introduction  
Chitin, which is biopolymer extracted from sea creatures including crustaceans of shrimps and crab shells, is the second most common polymer after cellulose on earth [1, 2]. Chitosan (Cs) is considered a deacetylated derivative of chitin [3]. It is a biodegradable non-toxic natural polymer. Chitosan has some unique features such as biocompatibility, biodegradability, non-toxicity, and complexing with metal ions [4]. Therefore, it is exploited universally in various applications such as in pharmaceuticals [5], the food industry [6], and water remediation [7]. Furthermore, the surface groups, namely, hydroxyl and amino groups, contribute to the hydrophilicity and active adsorption sites of Cs [8]. [PERSON] introduced the polycondensation reaction of resorcinol (R) with formaldehyde (F) to form a xerogel (X), which is named hereafter as RFX [9]. Xerogels are a kind of solid-formed gels, which are being synthesized through a slow drying process at room temperature with an unconstrained shrinkage [10]. The difference between aerogels and xerogels lies in the drying process, where the excess of solvent is extracted from the gel to obtain dry gels. Regarding aerogels, the solvent is removed by supercritical CO\({}_{2}\) extraction, which is a tedious technique that preserves the hierarchy of the pore structure formed in the gelation process. On the other hand, removing the solvent by convective drying at ambient conditions results in xerogels. In the later case, the micropores are preserved whereas the macro- and mesopores could collapse depending on the mechanical strength of the gel [11]. Xerogels are considered to be excellent support materials for metal and non-metal functional groups, and are utilized broadly in fuel cells due to their ability to exhibit controlled structures and adjustable pore sizes as well as their good stability [12, 13]. They are widely used in thermal insulation, nuclear particle detection, light guides, as wood adhesives, and electronic devices [14, 15, 16, 17, 18]. [PERSON] and [PERSON] [19] investigatedthe effect of catalyst amount on properties of RF xerogels and found that it has a significant effect on the pore structure. [PERSON] et al. [20] studied the effects of various parameters on the properties of melamine-resorcinol-formaldehyde xerogels and confirmed that they have a significant influence on the gel formation and its pore structure.  
Various studies in literature were mentioned that address mixing resorcinol-formaldehyde gels with different components. For instance, [PERSON] et al. [21] reported that the addition of polyacrylamideonitrile nanofibers into resorcinol-formaldehyde aerogels enhanced their thermal conductivity and other properties. [PERSON] et al. [22] investigated a mixed lignin-phenol-formaldehyde and found that the resulting pore-size distributions depended strongly on the initial composition, but not on the method of drying. [PERSON] et al. [23] studied the composite made of multi-walled carbon nanotubes with resorcinol-formaldehyde gels. The composite gels were synthesized by conducting the sol-gel reaction of resorcinol and formaldehyde in a suspension of carbon nanotubes in water, followed by CO\({}_{2}\) supercritical drying.  
Due to the importance and wide applications of both xerogels and chitosan, chitosan can import its unique features to xerogels and therefore widen their range of applications. Furthermore, the addition of chitosan to gels can make them more biodegradable and thus environment-friendly materials. The authors investigate here hybrid compounds of minor quantities of chitosan into RFX. Structure changes (such as lattice orders/defects, crystallinity, morphology, pore properties), thermal stability, chemical structure, and appearance of outcome hybrid products are investigated.