A water vapor sensor with 3D pillared metal–organic framework and 2D breathing mode

Abstract

Two 3D pillared metal–organic frameworks (MOFs) [Cd2(adc)2(bpp)3·4H2O]n (1) and [Cd2(adc)2(bpp)3]n (1b) with a 2D breathing mode of reversible dehydration–rehydration have been designed and synthesized. The dynamic behavior between 1 and 1b was detected by in situ single-crystal XRD analysis, which demonstrated that this 3D pillared MOF contracted and expanded in two dimensions accompanied by dehydration–rehydration. Additionally, 1b exhibited faster water vapor response compared to commercial silica gel desiccant at room temperature (21 °C) and humidity (RH% 50), which was detected by in situ IR spectrum. Therefore, the results suggests that this kind of flexible 3D pillared metal–organic frameworks of 1 and 1b would be a reliable sensor for monitoring water vapor. (H2adc = 4,4′-azodibenzoic acid, bpp = 1,3-Di(4-pyridyl)propane).