Organic Sol–Gel Synthesis: Solution‐Processable Microporous Organic Networks

Concentration is critical: Amine/isocyanate polycondensation below the critical gelation concentration cg affords a sol of growing microporous molecular-network nanoparticles rather than a gelated network (see picture, for model of particle: NCO red, NH2 blue, tetrahedral cross-link point gray). Further growth to form monolithic networks occurs on solvent evaporation, analogous to sol–gel synthesis of inorganic oxide networks.