Substrate-Assisted in Situ Confinement Pyrolysis of Zeolitic Imidazolate Frameworks to Nitrogen-Doped Hierarchical Porous Carbon Nanoframes with Superior Lithium Storage

Porous carbons generated from the direct pyrolysis of metal organic frameworks (MOFs) have shown great potential as a kind of promising electrode material for lithium-ion batteries (LIBs). However, several common drawbacks, such as the inevitable structural damage during carbonization process and intrinsic micropore-dominated feature of MOFs-derived products, largely impede the exposure of active sites and mass transfer, thus usually resulting in inferior electrochemical performances. In this work, an effective and controllable approach was reported to construct nitrogen-doped hierarchical porous carbon nanoframes (N-HPCFs) through in situ pyrolysis transformation of small-sized zeolitic imidazolate frameworks (ZIFs) that are in advance combined with a two-dimensional substrate templated from g-C3N4. Using this strategy, numerous ZIFs derived carbon nanoparticles appear to be well arranged on surfaces of a hollow carbon nanoplatelet produced by the adopted substrate after calcination, and the corresponding final product shows great improvements on both structural stability and pore distribution compared with that from direct pyrolysis of monodispersed ZIFs without the substrate. As expected, when used as the anode material for LIBs, the N-HPCFs electrode exhibits a high lithium storage capacity with good cycle stability (651 mAh g-1 after 400 cycles at the current density of 1 A g-1) and outstanding rate capability. Such enhanced electrochemical performances can be well ascribed to the stable frame structure as well as highly developed transport pathways for ions and electrons. So the synthetic strategy presented in this paper may pave a new way for the further application of ZIFs-based materials.