Water desalination offers a promising solution to the shortage of fresh water, which is among the most critical issues facing modern society. With molecularly precise porosity, covalent organic frameworks (COFs) are ideal candidate membranes for this purpose. Through molecular dynamics simulations, the Northwestern University MRSEC Super-Seed has studied the dependence of pore size dimension on the desalination properties of COF membranes. In particular, for pore sizes between 1 nm and 2.8 nm, COF membranes prevent the flow of sodium chloride ions while allowing for efficient transport of water molecules. This study thus identifies the optimal pore size range for desalination, which will inform the design of COF-based water purification membranes.