Moisture levels in closed or air-conditioned indoor spaces need to be regulated. Too much moisture can cause mold to grow, while too dry an environment can cause health problems for the inhabitants. The range for relative humidity (RH) recommended by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), for example, is 45–65 %. A material that can absorb water above these humidity levels and desorb it when the humidity drops below the recommended range would be useful. It could serve as an autonomous control mechanism for indoor moisture levels.
Mohamed Eddaoudi, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia, and colleagues have developed a metal-organic framework (MOF) that absorbs water at around 55–60 % RH and desorbs water at 45 % RH, making it suitable for the control of humidity in indoor spaces. The team combined 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (BTEB) with yttrium(III) nitride in the presence of 2-fluorobenzoic acid (2-FBA) to create the framework, called Y-shp-MOF-5 (shp = square hexagonal prism).
The material was characterized using X-ray crystallography and adsorption studies. The MOF retains its structure during the absorption and desorption of water for over 1000 cycles, and its moisture working range is suitable for keeping indoor moisture at recommended levels. This could be useful, e.g., in aircraft cabins, submarines, or space shuttles, and on a larger scale in air-conditioned buildings.
- A Fine-Tuned Metal–Organic Framework for Autonomous Indoor Moisture Control,
Rasha G. AbdulHalim, Prashant M. Bhatt, Youssef Belmabkhout, Aleksander Shkurenko, Karim Adil, Leonard J. Barbour, Mohamed Eddaoudi,
J. Am. Chem. Soc. 2017.