A two-dimensional hybrid coordination polymer [Pb(CH3NH2)I-2](n) featuring a well-defined layered structure is reported for scalable perovskite ink and deposition. This coordination polymer exhibits structural, spectroscopic, and physicochemical properties distinct from common PbI2 perovskite precursors. Notably, it serves as a methylamine "gas carrier" capable of liberating methylamine (CH3NH2) into the precursor solution, thus improving the solubility of perovskite in unconventional, greener processing solvents, such as acetonitrile. The purity of [Pb(CH3NH2)I-2](n) single crystals and the ability of the precursor to reduce sources of defects such as polyiodide species in solution allow the formation of high-quality perovskite films. This eventually results in efficient and stable devices, fabricated via a single-step antisolvent-free deposition method, transferable to large-area slot die coating. Gram scale synthesis of this unique lead precursor is demonstrated, essential for the scale-up of perovskite photovoltaic technology.