Surface Properties of Fluorine-Functionalized Metal-Organic Frameworks Based on Inverse Gas Chromatography

The introduction of the concept of surface propertiescan helpus to better analyze the basic physicochemical property changes ofmetal-organic framework (MOF) materials before and after fluorinefunctional group treatment. In this study, several polar and nonpolarprobes were selected to determine the surface properties, includingsurface-dispersive free energy, Lewis acid-base constants ofNi-MOF-74, and perfluoro carboxylic acid-modified Ni-MOF-74-Fn (n = 3, 5, and 7) in the range of 343.15-383.15K by inverse gas chromatography (IGC). It was observed that the surfaceenergy of the treated Ni-MOF-74-Fn showed a substantialdecrease with the growth of the perfluorocarbon alkyl chains and theincrease in surface roughness. In addition, Lewis acidic sites exposedby the Ni-MOF-74 material after adopting modification with fluorinefunctional groups increased with the increase of perfluorinated carboxylicacid chains, and their surface properties changed from amphiphilicacidic to strongly acidic. These results not only enrich the basicphysical property data of Ni-MOF-74 but also provide more theoreticalbasis for the fluorinated functionalized custom-designed MOFs andenrich their applications in the fields of multiphase catalysis, gasadsorption, and chromatographic separation.