No abstract

Although graphene nanomesh is an attractive 2D carbon material, general synthetic routes to produce functional graphene nanomesh in large‐scale are complex and tedious. Herein, we elaborately design a simple two‐step dimensional reduction strategy for exploring nitrogen‐doped graphene nanomesh by thermal exfoliation of crystal‐ and shape‐modified metal‐organic frameworks (MOFs). MOF nanoleaves with 2D rather than 3D crystal structure are used as the precursor, which are further thermally unraveled into nitrogen‐doped graphene nanomesh by using metal chlorides as the exfoliators and etching agent. The nitrogen‐doped graphene nanomesh has a unique ultrathin two‐dimensional morphology, high porosity, rich and accessible nitrogen‐doped active sites, and defective graphene edges, contributing to an unprecedented catalytic activity for the oxygen reduction reaction (ORR) in acid electrolytes. This approach is suitable for scalable production.

Porous organic frameworks (POFs), a general term for covalent‐organic frameworks (COFs), covalent triazine frameworks (CTFs), porous aromatic frameworks (PAFs), etc., are constructed from organic building monomers with strong covalent bonds and have generated great interest among researchers. The remarkable features, such as large surface areas, permanent porosity, high thermal and chemical stability, and convenient functionalization, promote the great potential of POFs in diverse applications. A critical overview of the important development in the design and synthesis of COFs, CTFs, and PAFs is provided and their state‐of‐the‐art applications in analytical chemistry are discussed. POFs and their functional composites have been explored as advanced materials in “turn‐off” or “turn‐on” fluorescence detection and novel stationary phases for chromatographic separation, as well as a promising adsorbent for sample preparation methods. In addition, the prospects for the synthesis and utilization of POFs in analytical chemistry are also presented. These prospects can offer an outlook and reference for further study of the applications of POFs.

Metal−organic frameworks (MOFs) and covalent−organic frameworks (COFs) are promising precursors for preparing high-performance carbonaceous materials for capacitive deionization (CDI). However, the simple pyrolysis of single MOFs or COFs usually leads to carbonaceous materials with disadvantages in salt adsorption capacity (SAC) and cycling stability, which are unfavorable to the further development of CDI. To address this issue, herein, we report the directed core−shell motif hybridization of COFs on MOFs to obtain selectively functionalized carbonaceous precursors, NH 2 -MIL-125(Ti) @TP-DQ COF, which then produce titanium dioxide nanoparticle-embedded nitrogenrich carbon architectures, called TiO 2 @COF, via pyrolysis. It is evidently expected that the resulting TiO 2 @COF possesses several advantageous features: (1) the inner core, which contains titanium dioxide nanoparticles, provides abundant faradic active sites for ion accommodation contributing additionally to the high SAC; (2) the outer capacitive shell, which is fibrous nitrogen-rich carbon, not only protects the inner core from the harsh environment of the solution and stabilizes the cycling performance but also affords plentiful nitrogen dopants for enhanced pseudocapacitive capacity and abundant pores for ion adsorption and electrolyte permeation; and (3) the outer COF-derived fibers interconnect with each other, giving rise to increasing electrical conductivity. As a result, TiO 2 @COF delivers a high SAC of 33.66 mg g −1 and favorable cycling stability over 40 cycles, significantly exceeding those of CDI electrodes derived from single MOFs or COFs. This work is expected to enrich the construction of selectively functionalized carbonaceous particles from MOFs and COFs and may also endow multiple promising applications of core−shell motif hybrids.