A solar-driven adsorbent based on Al-fumarate metal-organic framework coating with high water cycle efficiency

Abstract

Adsorption bed using pelleted metal-organic frameworks (MOFs) shows high water adsorption capacity, but have low adsorption/desorption rate, which limits the water cycling efficiency. And coating MOFs on the thermal-conductive surface can enhance the water adsorption/desorption rate by promoting heat transfer, furthermore, they can be efficiently driven by green solar light. Based on it, in this work, a novel mixed-solvothermal in-situ synthesis technology of Al-fumarate MOF coating on aluminum foil was developed. The results showed that by respectively adjusting the DMF/H2O ratios, fumaric acid molar contents, and the crystallization temperatures from 5/30–30/5, 2–10 mmol, and 90–120 °C, Al-fumarate MOF with uniform dispersion and controllable thickness (50–620 μm) on aluminum foil could be synthesized directly. The water release properties of different coatings under 1 and 1.2 sunlight (1 kW/m2 and 1.2 kW/m2) were tested. The results showed that the coating with different thicknesses can achieve complete desorption within 8–20 min at a sunlight intensity of 1.2 kW/m2, and the water yield through one cycle can reach 157 g/m2. The coating which displayed a thin strip cauliflower crystal morphology possessed a high adsorption capacity, fast adsorption/desorption rate, low desorption temperature as well as excellent cycle stability.