Dual-extended polyhedral MOF design achieves exceptional water stability and high adsorption capacity under low-humidity conditions

Access to clean water is still a major challenge around the world, especially in arid and semi-arid regions where humidity is low and traditional sources of water sources are scarce. Although metal-organic frameworks (MOFs) have great potential for atmospheric water harvesting due to their high surface area tunable porosity and versatile chemical functionality, their practical application has been limited by unsatisfactory water stability and insufficient adsorption capacity under dry conditions.

A union team of researchers from University of South China, ShanghaiTech University, and University of Aveiro has developed a new series of functionalized MOFs with high water stability, namely USC-CP-5-R (where R = -Cl, -OCH₃, -OH, -NH₂), in order to overcome these limitations. The results were published in Nano Research.

“By using a dual-extensions (both edge- and vertex-extension) strategy based on metal-organic polyhedra, we have constructed a series of highly connected, porous frameworks that exhibits exceptional hydrostability and enable precise tuning of their water affinities through the ligands’ functionalization,” said Xiao-Feng Wang, professor in School of Chemistry and Chemical Engineering at the University of South China and corresponding author of the study.

The team utilized the Cu₂₄-MOP-1 as the supermolecular building block (SBB), which was cross-linked with functional V-type organic spacers to construct a series of 14-connected porous networks USC-CP-5-R. These MOFs maintain crystallinity, structural integrity and porosity even after 24 hours in boiling water -a stability level comparable to that of zirconium-based MOFs.

The presence of functional groups with varying hydrophilicity (-Cl, -OCH₃, -OH, and -NH₂) enabled precise control of the water uptake behavior of USC-CP-5-R. Among them, the amino-functionalized one, USC-CP-5-NH₂, featured the best performance, achieving a water uptake of 38.5 wt% at 30% relative humidity and a saturation capacity of 0.59 g·g^-1.

Notably, the activated USC-CP-5-NH₂ could release 0.44 L of water per kilogram during a temperature swing adsorption process from 25 to 65 °C, and maintains a stable water uptake capacity over 100 cycles.

“This work provides not only a new candidate material for atmospheric water harvesting but also a general strategy for designing robust and tunable MOFs for applications in arid climates,” added Yue-Biao Zhang, professor in School of Physical Science and Technology at the ShanghaiTech University, and co-corresponding author.

The research team expects that the materials’ unique properties, including high water stability, excellent low-humidity uptake capacity, and remarkable cycling stability, make it as a highly promising adsorbent for practical atmospheric water harvesting.

This work was supported by funding from the National Natural Science Foundation of China, Hunan Provincial Natural Science Foundation, and the Science and Technology Commission of Shanghai Municipality.

About Nano Research

Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.