Zeolitic Imidazolate Framework-8 As a Reverse Osmosis Membrane for Water Desalination: Insight From Molecular Simulation

Over the past decade, metal-organic frameworks (MOFs) have emerged as a new class of porous materials and been considered as versatile materials for storage, separation, catalysis and other potential applications. In this work, a molecular simulation study is reported for water desalination in a MOF membrane composed of zeolitic imidazolate framework-8 (ZIF-8). The simulation demonstrates that water desalination occurs under external pressure, and Na⁺ and Cl^- ions cannot transport across the membrane due to the sieving of small apertures in ZIF-8. The flux of water permeating the membrane scales linearly with the external pressure, and exhibits an Arrhenius-type relation with temperature (activation energy of 24.4 kJ/mol). Compared to bulk phase, water molecules in ZIF-8 membrane are less hydrogen-bonded and the life time of hydrogen-bonding is considerably longer, as attributed to the surface interactions and geometrical confinement. This simulation study suggests that ZIF-8 might be potentially used as a reverse osmosis membrane for water purification.