We report on a design framework to aid in the development of system level considerations in metal organic framework (MOF) based atmospheric water harvesting. System level design considerations broadly refers to the engineering of MOFs and other sorbents into composites and packaging a plurality of such composites layers to create a practical AWH system. Prudent design practices are sought that maximize the daily water production (Lwater/kgsorbent/day) subject to the constraints posed by the adsorbent material and heat and mass transfer kinetics. Utilizing sorbent isotherm data and adsorption kinetics measurements for the sorbent/composite of choice, the complex relationship between a variety of adsorbent, adsorbent composite, and system packaging considerations can be explored to unveil optimal combinations. Optimal is subjective when designing a full-scale atmospheric water harvester, especially considering the wide range of applications and needs of the end user. We show that whether the limiting criteria is mass, cycles, volume, or energy consumption the optimal system design will vary significantly. In addition, the operating conditions of the AWH system, namely relative humidity, can change which combination of parameters is ideal. To demonstrate this framework, it has been applied to a theoretical system utilizing metal foam impregnated with aluminum fumarate creating a high efficiency sorbent composite. The isotherm data has been experimentally determined using dynamic vapor sorption and the adsorption kinetics of the foam has been modeled using a multiphysics model using coupled heat and mass transfer equations and the linear driving force approximation. This model has been validated for sample MOF-foam composites using dynamic vapor sorption. Furthermore, we show how this framework can be extrapolated to incorporate novel materials which have garnered interest for AWH applications.

Design considerations for the development of optimized metal organic framework (MOF)-based atmospheric water harvesting (AWH) systems

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