Imparting surface hydrophobicity to metal–organic frameworks using a facile solution-immersion process to enhance water stability for CO₂capture

Abstract

The water sensitivity of metal-organic frameworks (MOFs) poses a critical issue for their large-scale applications. One effective method to solve this is to provide MOFs with a hydrophobic surface. Herein, we develop a facile solution-immersion process to deposit a hydrophobic coating on the MOFs' external surface without blocking their intrinsic pores. The water contact angle of the surface hydrophobic (SH) MOFs is ∼146°. The hydrophobic coating not only greatly enhances MOFs' water stability but also provides durable protection against the attack of water molecules. When exposed to liquid water, the SH samples well retain their crystal structure, morphology, surface area and CO uptake capacity. However, the as-synthesized (AS) samples nearly collapse and lose their porosity as well as CO uptake capacity after the same exposure. This study opens up a new avenue for the MOFs' application of gas sorption in the presence of water.

Improving MOF stability: approaches and applications

“…[141][142][143][144] Qian et al successfully deposited a hydrophobic organosilicone layer on the exterior surface of MOFs via a facile solution-immersion process without any heat treatment. 141 Upon exposure to water for 5 days, it was found that the porosity of the MOFs HKUST-1, MIL-125, and ZIF-67 was retained to a great extent due to the enhanced hydrophobicity. Hou et al developed a postsynthetic polymerization method to form polymer brushes on the external surfaces of MOFs.…”

Fabrication of Pd/SiO2 with Controllable Wettability for Enhanced Catalytic Hydrogenation Activity at Ambient H2 Pressure

“…The wettability is one of the important surface properties and had attracted a lot of attentions recently . The activity and selectivity as well as the reaction pathway catalyzed by the heterogeneous catalyst could be adjusted, as the wettability of catalyst could regulate the affinity between the catalysts and the substrates, intermediates or products.…”

“…More and more efforts were put in how to regulate the surface properties for a better catalyst and the relationship between the surface properties and the catalytic effect was an attractive research topic.The wettability is one of the important surface properties and had attracted a lot of attentions recently. [4][5][6][7][8][9][10][11][12][13][14][15][16][17] The activity and selectivity as well as the reaction pathway catalyzed by the heterogeneous catalyst could be adjusted, as the wettability of catalyst could regulate the affinity between the catalysts and the substrates, intermediates or products. For example, the hydrophilicity of Ru catalyst was a necessary for the high selectivity of cyclohexene in the hydrogenation of benzene.…”

A new post-synthetic polymerization strategy makes metal–organic frameworks more stable

“…To overcome this instability issue and expand the practical applications of the existing MOFs, two main methods have recently been developed. [19][20][21][22][23][24][25][26][27][28][29] One is to functionalize the organic linkers of unstable MOFs with hydrophobic functionality. [19][20][21] For example, Cohen et al improved the hydrolytic stability of IRMOF-1, IRMOF-3 and MIL-53 through the introduction of hydrophobic alkyl groups such as isopropyl, isobutyl, and linear alkyl chains onto MOF ligands.…”