Water Adsorption in MOFs: Structures and Applications

Metal-organic frameworks (MOFs) are superior sorbents for water adsorption-based applications. The unique step-like water isotherm at a MOF-specific relative pressure allows easy loading and regeneration over a small range of temperature and pressure conditions. With good hydrothermal stability and cyclic durability, it stands out over classical sorbents used in applications for humidity control, water harvesting, and adsorption-based heating and cooling. These are easily regenerated at moderate temperatures using waste heat or solar heating. The isotherm thermodynamics and adsorption mechanisms are described, and the presence of MOFs in the water-air system is explained. Based on six selection criteria & AP;40 reported MOFs and one COF are identified for potential application. Trends and approaches in further synthesis optimization and production scale-up are highlighted. No-MOF-fits-all, each MOF has its own specific step location matching only with a certain application type. Most applications are technically feasible and demonstrated on the bench-scale or small pilot. Their maturity is benchmarked by their technology readiness level. Retrofitting existing applications with MOFs replacing classical desiccants may lead to rapid demonstration. Studies on techno-economic analysis and life cycle analysis are required for a rational evaluation of the feasibility of promising applications.

Automated summary

Metal-organic frameworks (MOFs) are highly effective sorbents for water-based applications, offering unique water isotherms and easy loading and regeneration. They are superior to classical sorbents in humidity control, water harvesting, and adsorption-based heating and cooling, with good hydrothermal stability and cyclic durability. Selection criteria and potential applications are discussed, highlighting the need for further optimization and scale-up. Retrofitting existing applications with MOFs shows promise, and techno-economic and life cycle analyses are necessary for evaluating feasibility.