Fluid–fluid interfaces in metal-organic frameworks

ABSTRACT

Grandcanonical Monte Carlo simulations in combination with successive umbrella sampling are used to study interfaces in the metal-organic frameworks (MOFs) IRMOF-1 and IRMOF-8. These interfaces are between coexisting phases of methane (CH) fluids that form on the surface of the framework structures of the latter MOF systems. Approaching the critical point of the corresponding demixing transition, the interfacial free energy as well as the interfacial width show a power-law scaling, as expected for the universality class of the three-dimensional Ising model. Capillary waves are strongly suppressed due to the external potential imposed by the framework structure. In IRMOF-8, density profiles of inhomogeneous systems with fluid–fluid interfaces show pronounced oscillations due to the crystalline framework structure.

GRAPHICAL ABSTRACT

KEYWORDS:

• Grandcanonical Monte Carlo simulation
• porous media
• fluid–fluid phase transitions

Acknowledgments

Computer time at the ZIM of the University of Düsseldorf is also gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

We thank Christoph Janiak for useful discussions. We acknowledge financial support by Strategischer Forschungsfonds (SFF) of the University of Düsseldorf [F 2012/279-2] in the framework of the PoroSys network.