Gauging van der Waals interactions in aqueous solutions of 2D MOFs: when water likes organic linkers more than open-metal sites

Molecular dynamics simulations combined with periodic electronic structure calculations are performed to decipher structural, thermodynamical and dynamical properties of the interfacedvs.confined water adsorbed in hexagonal 1D channels of the 2D layered electrically conductive Cu₃(HHTP)₂and Cu₃(HTTP)₂metal-organic frameworks (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene and HTTP = 2,3,6,7,10,11-hexathiotriphenylene). Comparing water adsorption in bulkvs.slab models of the studied 2D MOFs shows that water is preferentially adsorbed on the framework wallsviaforming hydrogen bonds to the organic linkers rather than by coordinating to the coordinatively unsaturated open-Cu²⁺sites. Theory predicts that in Cu₃(HTTP)₂the van der Waals interactions are stronger which helps the MOF maintain its layered morphology with allowing very little water molecules to diffuse into the interlayer space. Data presented in this work are general and helpful in implementing new strategies for preserving the integrity as well as electrical conductivity of porous materials in aqueous solutions.