Water in PHI Nanopores: Modeling Adsorption, Solvent Structure, and Thermodynamics

We modeled the uptake of water molecules into nanopores potassium-polyheptazineimide (K-PHI), a 2D covalent material that is one best water-splitting photocatalysts to date possessing experimentally reported strong binding. In current models, we find first are bound with −94.5 kJ/mol, i.e., twice cohesion energy and highest adsorption enthalpies so far. This binding proceeds unexpectedly on similar enthalpy level until pore filled, while strength passed through conjugated network. The tight also expressed in calculated, strongly shortened O–O distances, which average about 5% shorter than bulk water, corresponds much higher density, for structure above 1.1 g/ cm3. H-bridges aligned direction perpendicular planes, could give reasons observed ultrahigh ion fluxes conductivity K-PHI membranes. Decomposition components reveals an high charge transfer contribution, where partly naked K+ ions play key role. latter fact not only offers new structural lead motif design more strongly, but reversibly materials involving metal their surface puts cations as known cofactors enzymes light.