This report examined the factors related to the nature of polymerization to form two-dimensional (2D) conjugated polymer networks via a Stille cross-coupling reaction. Surprisingly, the resulting polymers were found to form graphene-like 2D nanosheets, and their solid-state morphologies were easily controlled by altering the adopted synthetic route such as either solvothermal or reflux reaction and solvents due to their weak intermolecular interactions. Typically, 2D polymers are categorized as covalent organic frameworks (COFs), which have been widely studied due to their unique structures and fascinating physicochemical properties. Neverthless, the high crystallinities of COFs limit their applications due to the strong intermolecular interactions. Therefore, we demonstrated how to reduce the crystallinity and control the morphology of 2D polymers, which is helpful to understand the physical attributes of the organic components contributing to the crystallinities of 2D polymers. In this contribution, we termed such low-crystalline 2D polymers as covalent organic nanosheets (CONs) to discriminate from COFs.