Assembly of graphene-wrapped ZIF-8 microspheres and confined carbonization for energy storage applications

Metal–organic frameworks (MOFs) are widely used as sacrificial templates to prepare MOF-derived porous carbons for energy storage applications. Herein, we discuss three critical issues in the synthesis of MOF-derived carbons: 1) the collapse and aggregation of carbonized MOFs, 2) the low electrical conductivity of MOF-derived sp³-dominated amorphous carbons, and 3) the controlled assembly of MOFs into a microspherical powder form. This study demonstrates a novel approach to simultaneously resolve these challenges, which includes intimately wrapping ZIF-8 with GO sheets, assembling the GO-wrapped ZIF-8 into microspheres via spray drying, and performing the confined carbonization of ZIF-8. The GO sheets act as both a structural and conductive scaffold to support the ZIF-8, thereby maintaining morphological stability, preventing aggregation during carbonization, and improving electrical conductivity. Notably, the microspherical assembly of carbonized ZIF-8 and reduced graphene oxide (rGO) shows a high compressive strength of 380 MPa, indicating that rGO as the structural scaffold reinforces the structural integrity of the microspherical assembly. Furthermore, electrochemical tests demonstrate the improved textural properties of the assembly. Our novel strategy provides a convenient yet efficient solution to the common critical issues with MOF-derived carbons for important energy storage applications.