Vapor-Phase Adsorption of Xylene Isomers and Ethylbenzene in MOF-74 Thin Films

Abstract

Thin films of Co-MOF-74 and Ni-MOF-74 were synthesized on Au-coated quartz crystal microbalance substrates by a vapor-assisted conversion (VAC) method that precludes the need for activation via postsynthetic solvent exchange. All thin films were structurally characterized by powder X-ray diffraction, reflection–absorption infrared spectroscopy, and Raman spectroscopy. Scanning electron microscopy (SEM) images reveal that the Ni-MOF-74 films exists as a dense base layer with hemispherical protrusions on the surface. In contrast, the scanning electron microscopy images of the Co-MOF-74 thin films show a rough surface with spherical deposits. The thin film morphologies were different than the powders resulting from the bulk synthesis. Gravimetric vapor-phase adsorption measurements for xylene isomers and ethylbenzene within Co-MOF-74 and Ni-MOF-74 thin films were conducted, and the results were compared with those reported for the corresponding bulk powders. Despite different morphologies, the saturation capacities of Ni-MOF-74 and Co-MOF-74 thin films were found to be nearly equivalent to those reported for the bulk powders. The results demonstrate that the VAC method can produce MOF-74 thin films that retain the intrinsic properties that are observed in bulk powders.

Vapor-phase methods for synthesizing metal-organic framework thin films

“…Acetic acid at the proper concentration and the diffusion rate determined the uniformity and crystallinity of the MOF film. Dana D. Medina et al 37 introduced the synthesis of a unique nanoscale architecture with pillar-like Co-CAT-1 MOF crystallites (Figure 3C). The gold film was deposited on stainless steel meshes (SSMs) via physical vapor deposition (PVD), and the resulting Au@SSM was used as a substrate for the VAC synthesis.…”

“…The array structures remained unchanged after gas phase crystallization with dimethylimidazole, while the surface experienced over- 36 (C) Schematic illustration of Co-CAT-1@Au@SSM preparation via VAC. 37 growth. Shohreh Fatemi et al 45 employed electrophoretic deposition to deposit zinc oxide on alumina tubes and vapor phase transfer technology to prepare ZIF-8 thin films (Figure 5B).…”

“…(B) XRD data for UiO-66(NH 2 ), UiO-67, UiO-68(NH 2 ), and PPPP−PIZOF-1 films 36. (C) Schematic illustration of Co-CAT-1@Au@SSM preparation via VAC 37.…”