Low-cost, green, large-scale, room-temperature, and fast synthesis of covalent organic frameworks (COFs) represents a highly desirable issue, due to both scientific and industrial interests, but remains a big challenge. The disadvantage of the established solvothermal method for COFs is now seriously restricting their practical industrial applications. We report herein aqueous synthesis of ketoenamine- and imine-linked COFs through a two-step dissolution–precipitation (DP) strategy. Impressively, using this DP method, we can prepare five ketoenamine-linked COFs and two imine-linked COFs in an ideal synthetic process with room temperature, 5 min reaction time, and large-scale products for one batch reaction, in the absence of acetic acid. These COFs show impressively high crystallinity and porosity and potential application in iodine and uranyl capture. This ideal synthetic route will pave a powerful methodology for making functional COFs with the value of practical industrial applications.