Investigation Of Water-Vapor Adsorption Onto Metal-Organic Frameworks (Mofs) For Greenhouse Air-Conditioning Application

Metal-organic frameworks (MOFs) are providing a new class of organic desiccant materials that possess interesting physical and adsorption characteristics. In this study, MOFs of type (i) HKUST-1, (ii) CPO-27(Ni), (iii) MIL-101(Cr) and (iv) MIL-53), are studied for greenhouse desiccant air-conditioning application. Water vapor adsorption equilibrium data of the MOFs are obtained from the literature. The adsorption equilibrium models of Dubinin-Astakhov (D-A) and Guggnheim-Anderson-de Boer (GAB) are used to represent the adsorption uptake data, and thereby adsorption isotherms are developed for various temperatures. Optimized parameters of the models are provided accordingly. Among the studied MOFs, the MIL-101(Cr) shows the highest water vapor adsorption uptake of 1.45 kg/kg at a relative pressure of 0.90 and temperature of 25 degrees C. The CPO-27(Ni) exhibits type-I adsorption isotherm according to IUPAC classification. Greenhouse air-conditioning application is studied for three demand categories based on required relative humidity of 60%, 40%, and 20%. Steady-state moisture cycled by the MOF based desiccant system is estimated. It has been found that different MOF adsorbents provide optimum desiccant unit based on available regeneration temperature. Results showed that the CPO-27(Ni) is not found applicable for required RH < 20%, whereas, MIL-101(Cr) and MIL-53 are applicable for all RH ranges.