Nano-Metal–Organic Frameworks Isolated in Mesoporous Structures

Abstract

As an alternative to bulk counterparts, metal–organic framework (MOF) nanoparticles isolated within conductive mesoporous carbon matrices are of increasing interest for electrochemical applications. Although promising, a “clean” carbon surface is generally associated with poor compatibility and weak interactions with metal/ligand precursors, which leads to the growth of MOFs with inhomogeneous particle sizes on outer pore walls. Here, a general methodology for in situ synthesis of eight nanoMOF composites within mesochannels with high dispersity and stability are reported. Mesoporous polydopamine (mesoPDA)-F127 nanospheres with unique surface chemistry, e.g., nanoconfined spaces, catechol functional groups, pyrrolic N doping, and hydrophilic PEO blocks, are found to be a suitable molecular platform. Sliced cross-sectional TEM, HAADF-STEM, and corresponding EDS elemental mapping, as well as nitrogen adsorption characterizations, are utilized to visualize the in situ growth process of ZIF-8 nanoparticles. These careful analyses provides direct evidence that the highly dispersed ZIF-8 is exclusively located inside the internal mesochannels. After moderate carbonization of the mesoPDA-F127/ZIF-8 nanocomposites, a prototype for a mesoporous carbon-isolated ZIF-8 nanostructure is achieved, which can regulate Zn²⁺ plating electrochemistry toward stable aqueous Zn batteries. This is the first report of the complete impregnation and even dispersion of nanoscale MOFs within the interior channels of mesoporous carbons.