Metal-Free Catalysis Using Carbon-Based Materials

Metal-free catalysts based on carbon materials have emerged as sustainable alternatives to traditional metal-based systems, offering cost-effective, environmentally benign routes to a broad array of chemical transformations. Their catalytic activity arises from intrinsic defects, heteroatom dopants and edge functionalities within graphitic architectures, which act as active centres for bond activation and electron transfer. These materials, encompassing graphene derivatives, doped nanocarbons and graphitic frameworks, exhibit remarkable versatility in oxidation, hydrogenation, dehydrogenation and transfer-hydrogenation reactions. By tuning the nature and distribution of active sites—such as assemblies of nitrogen atoms, carbon vacancies or co-doping with elements like sulfur and phosphorus—researchers have achieved high turnover frequencies, selectivity and recyclability under mild conditions. Advances in synthesis and theoretical modelling have clarified how electronic structure modulation and cooperative multisite interactions lower activation barriers, paving the way for practical applications in fine-chemical synthesis, biomass upgrading and green chemical processes.

Research from Nature Portfolio

Recent studies have demonstrated that nitrogen-assembly carbons with closely placed graphitic nitrogen sites can emulate transition-metal behaviour, effectively cleaving dihydrogen and catalysing hydrogenolysis of aryl ethers with outstanding selectivity for alkylarenes. Mechanistic and computational investigations showed that cooperating graphitic nitrogen dopants activate molecular hydrogen and facilitate subsequent transformations, highlighting the rational design of metal-free catalysts for challenging bond cleavages. Foundational work established that oxygen-containing groups on carbon materials serve as key active centres for borrowing-hydrogen reactions, enabling reductive amination of alcohols and reduction of nitroarenes without metal additives; surface analysis indicated that carbonyl functionalities coupled with high surface area confer durable activity over repeated cycles. Another line of enquiry revealed that carboxylic acid moieties on graphene oxide direct chemoselective aerobic oxidation of primary alcohols to either aldehydes or carboxylic acids under ambient conditions, with acid functionalities enhancing both reactivity and selectivity in oxidative and condensation processes.

Metal-Free Catalysis Using Carbon-Based Materials publication trend

The graph below shows the total number of articles in metal-free catalysis using carbon-based materials across all publications each year (not limited to Nature Index journals).

Technical terms

Doping: Introduction of heteroatoms (e.g. nitrogen, sulfur, phosphorus) into a carbon framework to modify electronic properties and create active sites.

Carbocatalyst: A catalyst composed entirely of carbon-based materials without metal components.

Turnover frequency: The number of substrate molecules converted per active site per unit time, indicating catalytic efficiency.

Graphitic nitrogen: Nitrogen atoms incorporated within the basal plane of graphitic carbon, contributing to electron density modulation around active centres.

Vacancy defect: A missing carbon atom in a graphitic lattice that generates a reactive site for adsorption and bond activation.

References

1. Nanocarbon catalysts with co‐active S−P−C sites enhance metal‐free direct oxidation of alcohols. SusMat (2024).
2. Active sites on graphene-based materials as metal-free catalysts. Chemical Society Reviews (2017).
3. Transition metal-like carbocatalyst. Nature Communications (2020).
4. Impact of Carboxyl Groups in Graphene Oxide on Chemoselective Alcohol Oxidation with Ultra-Low Carbocatalyst Loading. Scientific Reports (2017).
5. The dehydrogenation of butane on metal-free graphene. Journal of Colloid and Interface Science (2022).
6. Reduced Graphene Oxides as Carbocatalysts in Acceptorless Dehydrogenation of N‑Heterocycles. ACS Catalysis (2021).