Zeolites are crystalline aluminosilicate materials with a well-defined microporous structure, making them promising candidates for hydrogen storage applications. Their unique framework consists of interconnected SiO4 and AlO4 tetrahedra, forming uniform channels and cages that can adsorb hydrogen molecules. The presence of exchangeable cations within the pores further enhances their interaction with hydrogen, providing tunable adsorption properties.

The microporous structure of zeolites allows for physisorption of hydrogen through weak van der Waals interactions. The pore size, typically ranging from 0.3 to 1.5 nanometers, is well-suited for accommodating hydrogen molecules, which have a kinetic diameter of approximately 0.29 nanometers. The adsorption capacity is influenced by the zeolite's specific surface area, pore volume, and the nature of charge-balancing cations. For example, zeolites with alkali or alkaline earth metal cations exhibit stronger electrostatic interactions with hydrogen due to their higher charge density.

Hydrogen adsorption in zeolites is highly dependent on temperature and pressure. At cryogenic temperatures (77 K), zeolites can achieve moderate storage capacities, often in the range of 1 to 2 weight percent under pressures of up to 100 bar. However, at ambient temperatures, the capacity drops significantly due to the weak binding energy of physisorbed hydrogen, typically falling below 1 weight percent. Increasing pressure can improve uptake, but the gains diminish as the pores become saturated.

Modifications to zeolites can enhance their hydrogen storage performance. Ion exchange with smaller or more highly charged cations, such as lithium or magnesium, can strengthen the electrostatic interactions with hydrogen. Additionally, reducing the aluminum content in the framework can increase hydrophobicity, minimizing competitive water adsorption and improving hydrogen uptake. Post-synthetic treatments, such as dealumination or the introduction of transition metals, can further optimize pore accessibility and binding energy.

Compared to metal-organic frameworks (MOFs), zeolites offer distinct advantages in terms of cost and stability. MOFs exhibit higher surface areas and theoretically superior hydrogen storage capacities, but their synthesis often involves expensive organic linkers and metal precursors. Zeolites, in contrast, are produced from abundant raw materials using well-established industrial processes, making them more economically viable for large-scale applications. Furthermore, zeolites demonstrate superior thermal and chemical stability, retaining their structure under harsh conditions where MOFs may degrade.

Carbon-based materials, such as activated carbon and carbon nanotubes, also compete with zeolites for hydrogen storage. While carbons can achieve high surface areas and rapid adsorption kinetics, they lack the uniform pore structure and cation-mediated binding sites found in zeolites. The absence of tunable electrostatic interactions in carbons limits their hydrogen storage performance at ambient temperatures. Zeolites, with their well-defined chemistry and adjustable properties, provide a more controlled environment for hydrogen adsorption.

Despite these advantages, zeolites face challenges in achieving the high storage capacities required for practical applications. Research continues to explore advanced modifications, such as hierarchical pore structures and hybrid composites, to push the limits of their performance. By leveraging their inherent stability, cost-effectiveness, and tunable chemistry, zeolites remain a compelling material in the broader landscape of hydrogen storage technologies.

The future of zeolite-based hydrogen storage lies in optimizing their structural and chemical properties while maintaining scalability. Advances in synthetic techniques and a deeper understanding of hydrogen interactions at the atomic level will be critical in unlocking their full potential. As the hydrogen economy evolves, zeolites may play a key role in bridging the gap between laboratory-scale innovations and real-world deployment.