Two-dimensional (2D) materials have emerged as promising platforms for catalytic applications due to their unique electronic, structural, and surface properties. Among these, transition metal dichalcogenides (TMDCs) and graphene-based catalysts, such as platinum (Pt) supported on TMDCs or palladium (Pd) on graphene, exhibit exceptional performance in selective hydrogenation reactions. These reactions are critical in fine chemical synthesis, particularly for converting alkynes to alkenes or reducing nitroarenes to anilines—key intermediates in pharmaceuticals, agrochemicals, and specialty materials. The catalytic behavior of these systems is governed by substrate confinement effects, steric control, and electronic modulation, offering advantages over traditional metal catalysts in selectivity, stability, and efficiency.

The hydrogenation of alkynes to alkenes requires precise control to prevent over-hydrogenation to alkanes. Traditional metal catalysts, such as Pd or Pt nanoparticles on oxide supports, often suffer from poor selectivity due to uncontrolled active site geometries and strong adsorption of intermediates. In contrast, Pt/TMDC and Pd/graphene systems exploit the 2D substrate's confinement effects to tailor the reaction environment. The atomic thickness of TMDCs or graphene creates a constrained space around the metal nanoparticles, influencing the adsorption geometry of alkyne molecules. For example, Pt anchored on MoS2 exhibits a sulfur-rich coordination environment that weakens the binding of alkene products, reducing over-hydrogenation. Similarly, Pd nanoparticles on graphene benefit from the sp2-hybridized carbon lattice, which delocalizes electron density and modulates the Pd d-band center, lowering the activation barrier for selective hydrogenation.

Steric control is another critical factor in these systems. The planar structure of 2D materials restricts the accessibility of certain reaction sites, favoring the formation of specific intermediates. In the case of nitroarene hydrogenation, the flat surface of graphene or TMDCs ensures that nitro groups align parallel to the substrate, facilitating preferential adsorption and activation. This alignment minimizes side reactions, such as dehalogenation or ring hydrogenation, which are common with conventional Pd/C catalysts. Studies have shown that Pd/graphene achieves nitroarene conversion rates exceeding 95% with aniline selectivity above 90%, outperforming traditional catalysts where selectivity often falls below 80%.

Industrial fine chemical production demands catalysts that combine high activity with long-term stability. Traditional metal catalysts degrade under harsh conditions due to sintering, leaching, or poisoning. Pt/TMDC and Pd/graphene systems address these challenges through strong metal-support interactions (SMSI). The covalent bonding between Pt or Pd and the 2D substrate prevents nanoparticle aggregation, even at elevated temperatures. For instance, Pt/MoS2 retains over 85% of its initial activity after 50 reaction cycles in alkyne hydrogenation, while conventional Pt/Al2O3 loses more than 40% of its activity under identical conditions. The robustness of these systems is further enhanced by the inherent chemical resistance of TMDCs and graphene to acidic or basic environments, making them suitable for diverse industrial processes.

Electronic effects also play a pivotal role in catalytic performance. The charge transfer between metal nanoparticles and 2D substrates alters the electronic structure of active sites, optimizing their reactivity. In Pd/graphene systems, electron donation from graphene to Pd increases electron density at the metal surface, promoting the dissociative adsorption of hydrogen. This effect accelerates the hydrogenation kinetics while maintaining selectivity. Conversely, Pt on WS2 exhibits partial electron withdrawal from Pt to the TMDC, creating electron-deficient Pt sites that favor semi-hydrogenation of alkynes. These electronic modifications are absent in traditional catalysts, where the support's insulating nature limits tunability.

The industrial implications of these advancements are significant. Selective hydrogenation is a key step in producing fine chemicals, such as vitamins, fragrances, and pharmaceutical precursors. Conventional catalysts often require additional purification steps to remove over-hydrogenated byproducts, increasing costs and waste. Pt/TMDC and Pd/graphene systems reduce these inefficiencies by delivering higher selectivity in a single step. For example, in the synthesis of styrene from phenylacetylene, Pt/MoS2 achieves a styrene yield of 92% with minimal ethylbenzene formation, whereas Pd/C yields only 75% styrene with 20% ethylbenzene. This improvement translates to lower raw material consumption and reduced energy usage in downstream processing.

Despite these advantages, challenges remain in scaling up 2D material catalysts for industrial use. The synthesis of uniform, large-area TMDCs or graphene with consistent metal nanoparticle dispersion requires precise control over growth conditions. Techniques such as chemical vapor deposition (CVD) or atomic layer deposition (ALD) are promising but must be optimized for cost-effective production. Additionally, the long-term stability of these catalysts under continuous flow conditions needs further validation. Traditional catalysts, despite their limitations, benefit from well-established manufacturing protocols and lower initial costs.

In summary, Pt/TMDC and Pd/graphene catalysts represent a paradigm shift in selective hydrogenation, leveraging substrate confinement, steric control, and electronic modulation to outperform traditional metal catalysts. Their high selectivity, stability, and tunability make them attractive for industrial fine chemical production, though scalability and cost considerations must be addressed for widespread adoption. As research progresses, these 2D material-based systems are poised to redefine catalytic processes in the chemical industry.