The thermal decomposition of metal-organic frameworks (MOFs) into porous carbons represents a powerful strategy for creating high-surface-area materials with tunable porosity and functionality. MOFs, composed of metal nodes connected by organic linkers, serve as ideal precursors due to their well-defined crystalline structures and high carbon content. When subjected to controlled pyrolysis, these frameworks undergo carbonization while retaining their inherent porosity, yielding self-templated porous carbons with applications in energy storage and gas adsorption.

Pyrolysis of MOFs involves heating under inert or reducing atmospheres, typically between 600°C and 1000°C, leading to the decomposition of organic linkers and the formation of a carbonaceous matrix. The choice of MOF precursor significantly influences the final carbon morphology. For instance, zeolitic imidazolate frameworks (ZIFs), such as ZIF-8, decompose into nitrogen-doped porous carbons due to the imidazole-based ligands. The zinc nodes evaporate at high temperatures, leaving behind a highly porous carbon structure with a surface area often exceeding 1000 m²/g. Similarly, MOF-5, constructed from terephthalic acid and zinc clusters, pyrolyzes into carbon with a graphitic character, where the zinc oxide byproducts can be removed via acid washing to reveal a microporous network.

The retention of porosity during pyrolysis is attributed to the self-templating effect, where the original MOF architecture acts as a sacrificial template. The rigid framework prevents pore collapse, while the release of gaseous decomposition products generates additional micro- and mesopores. The carbonization temperature plays a crucial role in determining pore size distribution and graphitization degree. Lower temperatures (600–800°C) favor microporosity, while higher temperatures (900–1000°C) promote mesopore formation and increased electrical conductivity due to enhanced graphitic ordering.

Precursor chemistry dictates the resulting carbon morphology. MOFs with aromatic linkers, such as MOF-5, tend to form graphene-like sheets due to the preferential graphitization of benzene rings. In contrast, MOFs with aliphatic or heterocyclic linkers, such as ZIF-67 (cobalt-based), yield carbon nanotubes or nanofibers, as the metallic cobalt nanoparticles catalyze graphitic growth during pyrolysis. Doping is another critical factor; nitrogen-doped carbons derived from ZIFs exhibit improved electrochemical activity, while sulfur or phosphorus doping can further modify surface chemistry for specific applications.

In energy storage, pyrolyzed MOF carbons excel as electrode materials for supercapacitors and batteries. Their high surface area and tunable pore structure facilitate rapid ion transport, essential for high-power supercapacitors. Nitrogen-doped carbons from ZIFs demonstrate enhanced pseudocapacitance due to redox-active nitrogen functional groups, achieving specific capacitances exceeding 300 F/g in aqueous electrolytes. For lithium-ion batteries, the hierarchical porosity of MOF-derived carbons accommodates volume expansion during cycling, improving stability. When used as sulfur hosts in lithium-sulfur batteries, the porous structure mitigates polysulfide shuttling, leading to higher capacity retention.

Gas adsorption is another major application, leveraging the microporous nature of MOF-derived carbons. Their high surface area and chemical functionality make them effective for capturing CO₂, methane, and hydrogen. Nitrogen-doped carbons exhibit superior CO₂ uptake at low pressures due to strong interactions between CO₂ and basic nitrogen sites. For hydrogen storage, the narrow micropores (<1 nm) optimize physisorption at cryogenic temperatures, with uptake capacities reaching 2–3 wt% at 77 K and 1 bar.

The scalability of MOF pyrolysis is an advantage over traditional templating methods, which require additional steps to remove hard or soft templates. However, challenges remain in controlling the uniformity of pore size distribution and minimizing metal residue contamination. Advances in precursor design and pyrolysis protocols continue to refine the properties of these materials, expanding their utility in energy and environmental applications.

In summary, pyrolyzed MOFs represent a versatile class of porous carbons with tailored porosity and surface chemistry. Their self-templated formation simplifies synthesis while enabling precise control over structural and functional properties. For energy storage, they offer high-performance electrodes with exceptional conductivity and ion accessibility. In gas adsorption, their microporous networks provide efficient capture and storage capabilities. As research progresses, further optimization of MOF-derived carbons will unlock new opportunities in sustainable technology.