Vinylene-linked two-dimensional (2D) conjugated covalent organic frameworks, or 2D poly(arylene vinylene)s (2D PAVs), are promising polymer semiconductors for (opto-)electronics, photocatalysis and electrochemistry. However, conventional solvothermal synthesis often produces 2D PAVs that are poorly crystalline or difficult to access. Here we introduce a Mannich-elimination strategy that converts 8 2D imine-covalent organic frameworks into 11 highly crystalline 2D PAVs though a reversible C=C bond formation mechanism enabling precise crystallization control. This versatile approach affords robust 2D PAVs with honeycomb, square or kagome lattices, specific surface area up to ∼2,000 m² g⁻¹ and lattice-mismatch tolerance up to 3.5%. High-resolution transmission electron microscopy and continuous rotation electron diffraction reveal molecular-level ordering in a 2-µm-sized triphenylbenzene-based single-crystalline 2D PAV. We demonstrate that crystallinity profoundly influences charge transport, with benzotrithiophene-based 2D PAVs exhibiting charge mobilities tenfold higher than their amorphous analogues or 2D polyimine precursors. This work establishes a general route to highly crystalline 2D conjugated polymer materials for robust applications. (Figure presented.)