Tunable icephobicity of surface-grown metal–organic frameworks with nanohierarchical texture

TL;DR

This paper explores how metal-organic frameworks (MOFs) can be used to create icephobic surfaces that reduce ice formation and adhesion.

Contribution

The study identifies nanoconfinement and chemical functionalization as key factors in enhancing icephobic properties of MOFs.

Findings

Surface-grown MOFs lowered ice nucleation temperature by 4–5°C and reduced ice adhesion strength by up to two-thirds.

Nanoconfinement in sub-nanometre pores increases the energy barrier for ice nucleation and reduces ice contact.

Hydrophobic alkyl silane functionalization is the most effective strategy to enhance icephobic properties.

Abstract

Metal–organic frameworks (MOFs) have emerged as promising candidates for advanced surface treatments due to their inherent porosity, structural tunability, and functional versatility. Herein, we utilize these unique attributes of MOFs to systematically investigate their potential as passive icephobic surfaces, which is a critical requirement to mitigate ice accretion, which significantly impacts safety and performance across numerous technologies. Specifically, we elucidate how MOFs’ pore size, surface morphology, and chemical functionality synergistically influence ice nucleation temperature and ice adhesion strength. Employing surface-grown MOFs (UiO-66, UiO-67 and MOF-5), we demonstrate that these coatings consistently lowered the median ice nucleation temperature by approximately 4–5 °C and reduced ice adhesion strength by up to two-thirds compared to bare glass. Through a combined approach involving classical heterogeneous nucleation theory and density functional theory simulations, we uncover that the key mechanism driving this icephobic performance is the nanoconfinement effect arising from sub-nanometre pores, which significantly elevates the energy barrier to ice nucleation and minimizes solid-ice contact through the void effect. Furthermore, we identify hydrophobic alkyl silane functionalisation as the most effective chemical strategy to enhance these icephobic properties. These findings provide critical insights into the structure–property relationships that govern icephobic performance, paving the way for the rational design of MOF-based anti-icing coatings for diverse technological applications.

We identify the design limits of nanoconfinement in MOF based icephobic coatings. The findings demonstrate that once the pore size is small enough, chemical functionalisation becomes key to further suppressing ice nucleation and ice adhesion.

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