Hydrophobic Metal–Organic Frameworks

Abstract

formed from organic ligands and metal cations. [1][2][3][4][5][6][7][8][9][10] They are typically synthesized under mild conditions via coordinationdirected self-assembly processes and are also known as metal-organic coordination networks and porous coordination polymers. [11][12][13][14] Due to their high surface areas, large porosity, tunable pore sizes, and functionalities, MOFs have prospective applications in fields such as gas storage/separation, sensing or recognition, proton conduction, and magnetism. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] However, the advantageous unique structural features of even some of the best-performing MOFs are readily degraded because of their high moisture sensitivity, which may limit their practical applications. [29][30][31][32] Consequently, there is an ongoing search for highly hydrophobic, porous, sorbent materials to be employed in various large-scale applications in industry such as oil spill cleanup, hydrocarbon storage/separation, or water purification. [33][34][35][36][37] Many academics, industrial scientists, and engineers have therefore conducted research on the fabrication of superhydrophobic surfaces, which involves hydrophobic surface modification and creating surface roughness on the micrometer-or nanoscale. Hydrophobic surfaces are defined as substrates with an apparent contact angle greater than 90° with respect to water. On superhydrophobic materials, water droplets have contact angles above 150° and show very low adhesion because the drops partially rest on an air cushion. The surface energy and roughness govern the wettability of hydrophobic surfaces. In general, lower surface energies and higher roughness are associated with larger contact angles, lower contact angle hysteresis, and robust superhydrophobicity. Because of their ultralow surface energies (10-20 mN m −1 ), alkyl-based or fluorinated compounds are commonly used as hydrophobic modifiers to prepare surfaces with high intrinsic contact angles (>90°). [33][34][35][36][37][38][39][40][41][42] Recently, few methods have been developed for synthesizing hydrophobic MOFs including both pristine and composite systems. This review offers a comprehensive overview of the state of the art in hydrophobic MOF synthesis and the field's challenges and opportunities. Various synthetic strategies for preparing hydrophobic MOFs and their composites are introduced. We discuss the basics of wetting and critical challenges in the characterization of these hydrophobic materials. The potential applications of hydrophobic MOFs and related Metal-organic frameworks (MOFs) have diverse potential applications in catalysis, gas storage, separation, and drug delivery because of their nanoscale periodicity, permanent porosity, channel functionalization, and structural diversity. Despite these promising properties, the inherent structural features of even some of the best-performing MOFs make them moisture-sensitive and unstable in aqueous media, limiting their practical usefulness. This problem could be ...

One‐Pot Route for Fe@Poly(styrene‐co‐divinylbenzene) Foam with Robust Physical/Chemical Stability and Remote Magnetic Driven Capacity for Oil Removal

“…[14][15][16][17] Recently, superhydrophobic/ superoleophilic materials have gained special attention in oily wastewater purification driven by their unique surficial properties, which can allow oil to penetrate through but repel water out. [18][19][20][21][22][23] Hitherto, diverse methods have been developed to design superhydrophobic materials, according to models of wetting, [24][25][26][27] such as layer-by-layer method, [28,29] dip-coating route, [30][31][32] templates route, [33] spraycoating method, [34] and so on. [35][36][37] However, most existing superhydrophobic/superoleophilic materials can only remove oil from the water surface, preventing their applications in separating the heavy oil under the water.…”

Hydrophobic Metal–Organic Frameworks: Assessment, Construction, and Diverse Applications

“…The integrated attributions of the reported hydrophobic MOFs with respect to porosity, hydrophobicity and stability lead to great promise for this unique class of materials in diverse applications, including humid CO 2 capture, alcohol/water separation, pollutant removal from air or water, substrate‐selective catalysis, energy storage, anticorrosion coatings and self‐cleaning. Some excellent reviews about hydrophobic MOFs have been recently published . However, the goal of this contribution is to present a comprehensive review of the development and advancement of hydrophobic MOFs.…”

“…Some excellent reviews about hydrophobic MOFs have been recently published. [67][68][69][70] However, the goal of this contribution is to present a comprehensive review of the development and advancement of hydrophobic MOFs.In the following sections, the existing techniques for assessing the hydrophobicity of MOFs are first introduced, including the determination of crystal structure, water adsorption measurement, quantitative determination of the hydrophobicity index by the competitive breakthrough adsorption experiment of a hydrocarbon/water mixture, and water contact angle measurement. These measurements offer information about the extent of the hydrophobicity of MOFs at the internal pore surface or external crystal surface.…”

“…Some excellent reviews about hydrophobic MOFs have been recently published. [67][68][69][70] However, the goal of this contribution is to present a comprehensive review of the development and advancement of hydrophobic MOFs.…”

Controlling the Assembly of Protein Cages towards Functional Supramolecular Materials

“…Other non-covalent interactions such as transition metal coordination, hydrophobic interaction and protein-protein interaction have been utilized to obtain hierarchical structures. Metal coordination is widely used to construct metal-organic frameworks (MOF) for their application in separation, storage, and catalysis [93][94][95][96] . Inspired by the assembly of synthetic organic hybrid crystals, Ferritin was applied as building blocks for the construction of metal-protein cage crystals due to its feasibility for genetically engineered symmetrical metal-ion binding site ( Figure 2.8 A).…”