Direct synthesis of hierarchical porous polymer nanoparticles from nitrile monomers and its application for methylene blue adsorption

Abstract Microporous covalent triazine-based frameworks (CTFs) have been widely used as adsorbents, separation and catalysts in the past few years, but the confined microporous network often induces diffusion limitations of molecules to and from the active sites. Here, we present a general bottom-up synthetic strategy to produce hierarchical porous polymer nanoparticles by cyclotrimerization of 1,4-dicyanobenzene in molten ZnCl₂. Controlling the ratio of monomer to molten salts is the key to prepare hierarchical porous polymer nanoparticles by ionothermal methods, and uniform nanoparticles with particle size of 100–400 nm can be facilely synthesized at a low monomer/ZnCl₂ molar ratios. The resulting hierarchical porous polymer nanoparticles exhibit great adsorption capacity of methylene blue. The enhancement is ascribed to enhanced mass transfer of the molecules and easy access to the active sites as a result of the short diffusion lengths of hierarchical porous polymer nanoparticles. This method is simple and efficient for the preparation of size-controllable hierarchical porous polymer nanoparticles from nitrile monomers, which is conducive to expand its application in adsorption, catalysis and other related fields.