Cation exchange (CE) has been emerged as a promising post-synthesis strategy of colloidal nanocrystals. However, it is unclear how the cation precursor affects the CE process and the final colloidal nanocrystals. Herein, we utilized two Zn-B Lewis acid-base adduct complexes (B = oleylamine (OAM) and methanol (MeOH)) as Zn precursors for CE with Ag₂S quantum dots (QDs). Our study revealed that the steric hindrance and complexing capabilities of Zn precursor significantly affect the CE kinetics. As a result, the Zn-doped Ag₂S (Zn:Ag₂S) and Ag₂S@ZnS core–shell QDs were successfully obtained with enormous enhancement of their photoluminescence (PL) intensities. Theoretical simulation showed that the Zn-OAM with higher desolvation energy and spatial hindrance tended to form doped Zn:Ag₂S QDs due to the inefficient cation exchange. Whereas the Zn-MeOH with lower exchange barrier promoted the conversion of Ag-S to Zn-S, thus forming Ag₂S@ZnS core–shell QDs. We anticipate that this finding will enrich the regulatory approaches of post-synthesis of colloidal nanocrystals with desirable properties.