Coordination‐Driven Assembly of Metal–Organic Framework Coating for Catalytically Active Superhydrophobic Surface

Abstract

Here, a superhydrophobic and catalytically active metal–organic framework (MOF) coating is reported by coordination‐driven assembly of MOF nanoparticles and a catechol‐functionalized polysiloxane polymer. This MOF coating can be fabricated by casting MOF‐polymer precursor onto diverse substrates with varied coating techniques, for example, spray coating, bar coating, and dip coating. The catechol‐functionalized polymer can not only coordinate to the open metal sites on MOF surface which enables the surface functionalization and assembly of MOF nanoparticles, but also allow non‐covalent interactions with casting substrates—thus improving the substrate adhesion of the MOF coating. With the well‐preserved porosity and surface hydrophobicity, the MOF coating demonstrates superhydrophobicity as well as improved catalytic activity toward the Knoevenagel condensation at room temperature. Such coordination‐driven assembly approach can be extended to a range of MOF systems for preparing highly functional composite materials toward various applications.

Recent Improvement Strategies on Metal-Organic Frameworks as Adsorbent, Catalyst, and Membrane for Wastewater Treatment

“…PDMS coating method is also powerful to increase hydrophobicity of other MOFs, such as ZIF-67 and MIL-125, from the WCA of 0 • (their pristine form) to 146 • (PDMS-coated ZIF-67) and 141 • (PDMS-coated MIL-125), respectively. In a separate work, Yi et al used catechol-functionalized PDMS (PDMS-Cat) also showed hydrophobicity improvement of ZIF-8 from the WCA of 0 • (pristine form) to 126 • (PDMS-Cat coated ZIF-8) [48]. Interestingly, stronger hydrophobicity was observed when PDMS-Cat-coated ZIF-8 casted on the carbon cloth substrate (WCA of 156 • ) since the excess PDMS-Cat that were present in the mixture will form a network and homogeneous MOF coating on the substrate.…”

“…It is noteworthy that both researchers reported that PMDS [47] or PDMS-Cat [48] coating not only boost hydrophobicity of the MOFs, but also retain their catalytic performance in the presence of water molecules.…”

“…Interestingly, stronger hydrophobicity was observed when PDMS-Cat-coated ZIF-8 casted on the carbon cloth substrate (WCA of 156°) since the excess PDMS-Cat that were present in the mixture will form a network and homogeneous MOF coating on the substrate. It is noteworthy that both researchers reported that PMDS [ 47 ] or PDMS-Cat [ 48 ] coating not only boost hydrophobicity of the MOFs, but also retain their catalytic performance in the presence of water molecules.…”

A Highly Selective Supramolecule Array Membrane Made of Zero‐Dimensional Molecules for Gas Separation

“…However, it remains a challenge to induce site‐specific nucleation of mim and to promote templated assembly of such organic molecules into ordered membranes. With this challenge in mind, we noted that metal–organic frameworks (MOFs) with open metal sites favor a binding of organic molecules, for example, organic molecules with N atoms, [24–26] through metal‐donor bonds, and the abundance of active metal sites surrounding external MOF surface underpins the coordinative linkage of polymers, [27, 28] bio‐molecules [29] and growth modulators [30] on MOFs to achieve surface coating, functionality ligation and definite core–shell structures. Inspired by these early manipulations on MOFs with open metal sites, we employed a facile vapor‐sublimation‐crystallization (VSC) process [31] to assemble mim SAMs on such layers of MOFs.…”

“…As aproof-of-concept, we proposed supramolecule array membranes (SAMs) with mim as the molecular building blocks.However,itremains achallenge to induce site-specific nucleation of mim and to promote templated assembly of such organic molecules into ordered membranes.W ith this challenge in mind, we noted that metal-organic frameworks (MOFs) with open metal sites favor ab inding of organic molecules,for example,organic molecules with Natoms, [24][25][26] through metal-donor bonds,a nd the abundance of active metal sites surrounding external MOF surface underpins the coordinative linkage of polymers, [27,28] bio-molecules [29] and…”