Preferred catalysis distinctly determined by metals doped with nitrogen in three-dimensionally ordered porous carbon materials.

Three-dimensionally ordered nanoporous structures were generated in carbon materials doped with metals and nitrogen as catalytically active sites for electrochemical reactions. Free-base and metal phthalocyanines with a strategically designed molecular structure were used as carbon sources to obtain an ordered porous structure via homogeneous self-assembly with Fe3O4 nanoparticles as the pore template and the prevention of melting away during carbonization. The doping of Fe and nitrogen was achieved by a reaction between the free-base phthalocyanine and Fe3O4 through carbonization at 550 °C, while Co and Ni were doped using the corresponding metal phthalocyanines. The preference of these three types of ordered porous carbon materials for catalytic reactions was distinctly determined by the doped metals. Fe-N-doped carbon showed the highest activity for O2 reduction. Additional heat treatment at 800 °C enhanced this activity. CO2 reduction and H2 evolution were preferred by the Ni- and Co-N-doped carbon materials, respectively. A change in the template particle size was capable of controlling the pore size to enhance mass transfer and improve performance. The technique presented in this study enabled systematic metal doping and pore size control in the ordered porous structures of carbonaceous catalysts.

Ordered carbonaceous frameworks: a new class of carbon materials with molecular-level design.

Ordered carbonaceous frameworks (OCFs) are a new class of carbon materials with a three-dimensional ordered structure synthesized by simple carbonization of metalloporphyrin crystals with polymerizable moieties. Carbonization via solid-state polymerization results in the formation of graphene-based ordered frameworks in which regularly aligned single-atomic metals are embedded. These unique structural features afford molecular-level designability like organic-based frameworks together with high electrical conductivity, thermal/chemical stability, and mechanical flexibility, towards a variety of applications including electrocatalysis and force-driven phase transition. This feature article summarizes the synthetic strategies and characteristics of OCFs in comparison with conventional organic-based frameworks and porous carbons, to discuss the potential applications and further development of the OCF family.

Helically aligned fused carbon hollow nanospheres with chiral discrimination ability.

While the functions of carbon materials with precisely controlled nanostructures have been reported in many studies, their chiral discriminating abilities have not been reported yet. Herein, chiral discrimination is achieved using helical carbon materials devoid of chiral attachments. A Fe3O4 nanoparticle template with ethyl cellulose (carbon source) is self-assembled on dispersed multiwalled carbon nanotubes (MWCNTs) fixed in a lamellar structure, with helical nanoparticle alignment induced by the addition of a binaphthyl derivative. Carbonization followed by template removal produces helically aligned fused carbon hollow nanospheres (CHNSs) with no chiral molecules left. Helicity is confirmed using vacuum-ultraviolet circular dichroism spectroscopy. Chiral discrimination, as revealed by the electrochemical reactions of binaphthol and a chiral ferrocene derivative in aqueous and nonaqueous electrolytes, respectively, is attributable to the chiral space formed between the CHNS and MWCNT surfaces.

Force-responsive ordered carbonaceous frameworks synthesized from Ni-porphyrin.

Force-responsive ordered carbonaceous frameworks (OCFs) are synthesized for the first time. Carbonization of Ni porphyrin monomers having eight polymerizable ethynyl groups yields OCFs with atomically dispersed divalent Ni species and developed micropores. The highest specific surface area (673 m2 g-1) among the OCFs has been achieved. The OCFs thus synthesized comprise non-stacked graphene sheets, affording a unique mechanical flexibility that enables force-driven reversible phase transition.