CuPS was firstly synthesized by using the cationic exchange method [93]. The cations of copper tetraamine complex [Cu(NH3)4(H2O)2]2+ were dissolved and then deposited on a silica surface at room temperature. The cationic exchange method is usually accompanied by a deposition-precipitation step because the formation of CuPS was proposed to be a sequential process through the dissolution of silica followed by the precipitation of phyllosilicates. Toupance et al. [40] proposed that the formation mechanism of CuPS is through the selective adsorption of neutral Cu complexes (i.e., Cu(OH)2(H2O)2) on a silica surface). Therefore, the cationic exchange was renamed as selective adsorption. Later, Chen et al. [73] reported an ammonia evaporation (AE) method for CuPS synthesis. In this process, silica sol was mixed with a copper ammonia complex (initial pH value at about 11–12), followed by the gradual removal of ammonia through evaporation till the solution is neutralized, yielding CuPS as the precipitates.