The interaction between H-2 molecules within the structure of microporous clays is an interesting topic, with applications including gas storage, nuclear waste containment, and geochemistry. Microporous clays exhibit an intricate atomic structure with different polar species able to interact with H-2. However, despite its numerous implications, the binding mechanism of H-2 has not been discussed in detail. In this work, a first-principles study of the structure, energetics, and chemical bonding of the H-2 in palygorskite clay is addressed. Total energy calculations including van der Waals interactions shown that, depending on water content, the structural channels of palygorskite clays offer different possibilities for the adsorption of H-2. The calculated binding energies range between 6 and 24 kJ/mol. The larger H-2 binding affinity corresponds to the case where the Mg2+ nearest to the inner surface of the palygorskite channel is exposed due to a partial loss of coordination water. The analysis of net atomic charges predicts a slight charge transfer from H-2 to Mg2+. Electronic structure and overlap population analysis reveal orbital interactions between the 3s and 3p states of Mg2+ with the a orbitals of the H-2 molecule, explaining the charge transfer and large binding energy in this system (24 kJ/mol). In contrast, Al3+ does not induce charge transfer from H-2, while dispersion forces and electrostatic interactions dominate the binding mechanism. The results of the present study suggest that the controlled dehydration of coordinated water in Mg-rich palygorskite is a potential route to the creation of microporous materials with enhanced gas adsorption. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.