The copper‐catalyzed azide–alkyne cycloaddition (CuAAC) click reaction is among the most extensively used strategies for the post‐polymerization modification of COFs. This work shows a new procedure for the postsynthetic functionalization of imine‐based COFs by using a heterogeneous solid–gas reaction between alkyne‐functionalized COFs and azides in the absence of a copper catalyst. This new alternative represents a step forward towards a greener postsynthetic modification of COFs opening a high potential for the development of new applications. Click! Postsynthetic functionalization of imine‐based COFs is carried out at the solid–gas (COF–azide) interface, without solvent and catalyst, in high yield. This procedure is a green postsynthetic modification of COFs and allows for the preparation of 2D materials with high potential for the development of new applications.