Metal–organic frameworks with high working capacities and cyclic hydrothermal stabilities for fresh water production

Abstract

In this work, we evaluated the working capacities of eight hydrothermally stable metal–organic frameworks (MOFs) for water adsorption under typical humidity conditions in three representative dry regions. Remarkably, three MIL-100(M) materials (M=Cr, Al, and Fe) and MIL-101(Cr) exhibited very high working capacities for medium and high humidity conditions due to their large surface areas. All of the MOFs consisting of only MIII sites (MIL-101(Cr), MIL-100(Cr), and MIL-100(Al)) showed good cyclic water adsorption/desorption performances and good hydrothermal stabilities. Due to the presence of FeII sites formed during activation at 250°C, MIL-100(Fe) showed a considerable decrease in its water adsorption isotherm during the 2nd cycle although almost unchanged water uptakes were observed in the following cycles. When MIL-100(Fe) was activated at 150°C (MIL-100(Fe)_150) to prevent formation of FeII sites, the sample showed good cyclic adsorption/desorption performance and good hydrothermal stability. Considering the high working capacities, cyclic adsorption/desorption behaviors, and good hydrothermal stabilities, MIL-101(Cr), MIL-100(Cr), MIL-100(Al) and MIL-100(Fe)_150 are promising adsorbents for producing drinking water in dry regions with medium or high humidity conditions during the night.