Chitosan is a very well-known biocompatible and biodegradable polysaccharide consisting of β-(1–4)-linked glucosamine units, derived from the deacetylation of chitin. This unique biopolymer consists of primary amines as well as hydrophilic hydroxyl groups along with the chitosan backbone and has exceptional properties and wide applications. Numerous articles have been devoted to the preparation and properties of chitosan-based biomaterials, which have been demonstrated as beads, films, fibers (2D-scaffolds), gels, sponges (3D-scaffolds), and wound-healing materials. The unusual adsorption capacity of chitosan cross-linked polymer is demonstrated by trapping cations, anions, organic dyes, and pharmaceutical ingredients from wastewater. The most striking manifestations of flexibility in the preparation of these adsorbents have been critically reviewed, and their sorption efficiencies compared. Notably, these materials are also used as drug delivery carriers. Further, various metal-loaded chitosan-based nanocomposite materials have been used efficiently in organic catalytic reactions. As per the rich literature survey, such chitosan-based materials warrant further research due to their abundance, eco-friendliness, and effectiveness towards commercialization. The biotechnological aspects of chitosan may lead to promising low-cost materials and by-products of industrial and agricultural significance. The constant demand for potential adsorbents for the removal of pollutants, can be met by fine-tuning the structural properties of chitosan with appropriate cross-linkers or additives. Graphic abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.