Construction of hollow metal-organic frameworks and their derived complex carbon-based nanoreactors for electrochemical conversion and energy storage

Cells in nature exhibit intricate soft matter structures, characterized by microcompartments housing specific functional groups. Various chemical reactions that are essential for life occur in a regulated, organized, and oriented way. It has been deeply revealed that the special structure features of natural cells play a dominant role in these reaction procedures. In materials science, nanoreactors designed by simulating cellular behaviors can serve as "artificial cells" to facilitate controlled catalysis of chemical reactions. These cell-mimicking nanoreactors provide a mesoscale-confined space where chemical reactions occur in regulated spaces. Over recent decades, nanoreactors with intriguing physicochemical properties have captured significant interest across diverse research domains, including heterogeneous catalysis, energy storage and conversion, environmental remediation, and biochemistry. Among various nanostructured materials, nanoreactors are most represented by hierarchical porous and multilevel hollow nanomaterials. Based on such innovative nanostructures, there are key structural features as follows: (1) The spatial arrangement of porous structures and cavities within nanoreactors enables the attachment of functional groups at desired locations; (2) micro/mesoporous and hollow cavities provide confined space for concentrating the reactants through selective interactions, trapping reaction intermediates on active sites for further reactions, and enhancing mass transfer and selective sieving based on the specific pore structure; (3) integrating spatially separated active sites within a single particle enable more efficient cascade reactions. Therefore, nanoreactors exhibit unique structural features and high catalytic efficacy, positioning them for promising applications. A typical nanoreactor design for the catalytic process should take both mass diffusion and surface reactions into account, which requires that the structure and composition of the nanoreactor should be precisely controlled. Based on these considerations, metal-organic frameworks (MOFs), assembled from coordination between metallic nodes and multitopic organic ligands, offer an intriguing avenue for nanoreactor fabrication. MOFs typically have high porosity and modular assembly modes, so they can be customized for specific applications through top-up synthesis or selective etching via top-down processing to fabricate hierarchical porous and multilevel hollow nanomaterials. After pyrolysis, MOFs-derived carbon-based nanomaterials serve as effective nanoreactors. Based on this intrinsic property, MOFs-derived carbon-based nanomaterials have been fabricated and used as nanoreactors for downstream catalytic applications over the past few decades. Here, the synthesis strategies for MOFs-derived carbon-based nanoreactors were comprehensively summarized and discussed, including "bottom-up" assembly strategy, "top-down" chemical tailoring, and confined pyrolysis strategies. Then, their corresponding applications in electrochemical energy conversion and storage with the advantageous nanoreactor effects were highlighted. Finally, several future perspectives for MOFs-derived nanoreactors were proposed.