Reactive-template induced in-situ hypercrosslinking procedure to hierarchical porous polymer and carbon materials

Porous polymers have attracted increasing research interest because of their potential to merge the properties of both porous materials and organic polymers. As a novel class of porous polymers, hierarchical porous polymers (HPPs) that simultaneously possess micro-, meso-, and/or macropores are expected to exhibit the advantage of each class of hierarchical pores in a synergistic manner and thus are currently finding wide applications in many fields including energy, environment, catalysis, adsorption, and medicine. However, easy fabrication of well-defined hierarchical porous polymers remains a great challenge. Herein, we successfully developed a facile and effective procedure of reactive-template induced in-situ hypercrosslinking for fabrication of a novel class of hierarchical porous polymer. The key to this procedure is design and employment of SiO₂ nanospheres containing 4-(chloromethyl)phenyl groups as the reactive templates. The 4-(chloromethyl)phenyl groups on the surface of the reactive SiO₂ nanosphere templates can react with the self-crosslinkable monomer 1, 4-dichloro-p-xylol (DCX) to in-situ form a stable covalent bond at their interface. Such a strong covalent interaction facilitates the hypercrosslinking of DCX onto the surface of SiO₂ nanospheres, thus leading to high monodispersion of SiO₂ nanosphere templates and formation of uniform polymeric coating. The as-prepared HPP contains three types of pores: (i) micropores induced by hypercrosslinking of DCX, (ii) meso-/macroporous network formed through the crosslinking of reactive moiety on the periphery of colliding nanospheres with each other in various directions, and (iii) well-defined macropores obtained by removal of sacrificial silica nanospheres. Furthermore, the hypercrosslinked structure characteristic of HPP ensures good carbonization transformation and nanomorphology stability during heating treatment at high temperatures, leading to the formation of hierarchical porous carbon (HPC). New micropores of about 0.6 nm in diameter are generated during carbonization, possibly because of burn-off of noncarbon elements and carbon-containing compounds or disordered packing of microcrystalline carbon sheets and clusters. These HPP and HPC materials could hold considerable promise in applications as advanced adsorbents, catalyst supports, energy-storage materials and others. We hope that the reactive-template induced in-situ hypercrosslinking strategy may open the doors for preparation of various advanced hierarchical porous materials.