Phys.org December 12, 2024
While the accessible pores render an enormous variety of functionalities to the bulk of metal–organic frameworks (MOFs), the outer surfaces exposed by these crystalline materials also offer unique characteristics not available when using conventional substrates. An international team of researchers (Germany, India) fabricated superhydrophobic substrates with static water contact angles over 160° by grafting hydrocarbon chains to well-defined MOF thin films (SURMOFs) prepared using layer-by-layer methods. A detailed theoretical modelling of the hydrocarbon chains grafted on the outer SURMOF surface with well-defined spacing between anchoring points revealed that the grafted hydrocarbon chains behaved similarly to polymer brushes during wetting, where conformational entropy was traded with mixing entropy. The chains were coiled and could access many different conformations. The entropic contributions led to a pronounced reduction of the surface free energy, rendering superhydrophobic properties to the functionalized SURMOFs. The water adhesion strength could be decreased by increasing the surface roughness on the nanometer scale… read more. Open Access TECHNICAL ARTICLEÂ
Porous substrate with a small water contact angle… Credit: Karlsruhe Institute of Technology