Abstract
Three-dimensional carbon-based structures have proven useful for tailoring material properties in structural mechanical and energy storage applications. One approach to obtain them has been by carbonization of selected metal–organic frameworks (MOFs) with catalytic metals, but this is not applicable to most common MOF structures. Here, we present a strategy to transform common MOFs, by guest inclusions and high-temperature MOF–guest interactions, into complex carbon-based, diatom-like, hierarchical structures (named for the morphological similarities with the naturally existing diatomaceous species). As an example, we introduce metal salt guests into HKUST-1-type MOFs to generate a family of carbon-based nano-diatoms with two to four levels of structural hierarchy. We report control of the morphology by simple changes in the chemistry of the MOF and guest, with implications for the formation mechanisms. We demonstrate that one of these structures has unique advantages as a fast-charging lithium-ion battery anode. The tunability of composition should enable further studies of reaction mechanisms and result in the growth of a myriad of unprecedented carbon-based structures from the enormous variety of currently available MOF–guest candidates.
Highlights
We present an approach based on metal−organic frameworks (MOFs)−guest precursors and show a general strategy to transform common MOFs into carbon-based structures with multiple levels of hierarchy via a simple thermochemical treatment
We study in detail the Cu-based MOF [HKUST-1(Cu),[37,38] A1] impregnated with a Mo-based guest, ammonium tetrathiomolybdate,39 [(NH4)2MoS4, ATM], in dimethylformamide (DMF) solution to form our MOF−
In addition to exploring a range of carbonaceous hierarchical structures derived from MOF−guest precursors, we demonstrated the potential usefulness of these new 3D carbon-based materials, the B2, as lithium-ion battery anode (LiB) materials
Summary
Three-dimensional carbon-based structures with multilevel hierarchy[1−7] from low-dimensional nanostructured building blocks (e.g., carbon dots, fullerenes, nanofibers/tubes, and graphene) can greatly exceed the properties of bulk carbon materials in numerous applications, such as lightweight but strong structures[4] and energy storage.[5−8] Multistep procedures and complex templates are commonly used to fabricate these materials, but few structures with multilevel hierarchy have been formed via facile bottom-up approaches.[3,5] Recent work has explored carbonizing metal−organic frameworks (MOFs)[7−15] and in a few cases with Ni, Co, Fe, and other catalytically active metals centers (as a part of the MOF’s secondary building unit) has resulted in carbon-fiber assemblies.[16−23] Guest incorporation in the open porous. We produce a family of carbon-based “nano-diatoms” with ordered hierarchical structures and investigate the combined effects of substituting the MOF or guest with control over the morphology of the resulting carbonaceous material. Other inorganic elements/compounds introduced from both guests and MOF hosts can be incorporated into the pyrolyzed products (i.e., nano-diatoms). Further exploration of this hightemperature guest-induced phenomena on the broad range of available MOF−guest combinations[36] will allow bottom-up fabrication of a new class of 3D structures with multilevel hierarchy for practical use in energy storage, energy conversion, and sensing
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