A method for producing porous particles of a cross-linked polymer, and porous particles that can be produced according to the method are disclosed. The porous particles of a crosslinked hydroxy- or amino-group-containing polymer have a relatively low swelling factor. A composite material contains the porous particles dispersed in a continuous aqueous phase. The porous particles, or the composite material, are used for purifying organic molecules and for bonding metals from solutions. A filter cartridge contains the porous particles of a cross-linked polymer or the composite material.