Amine-Functionalized CAU-10–Based Electrospun Hygroscopic Membrane for Atmospheric Water Harvesting

Metal–organic frameworks (MOFs) are promising sorbents for atmospheric water harvesting (AWH) owing to their adjustable porosity and reversible adsorption properties. Aluminium-based CAU-10 exhibits excellent hydrothermal stability but has limited water uptake at low relative humidity (RH). Here, a bifunctional electrospun membrane integrating amine-functionalized CAU-10 (CAU-10-H/NH₂) with polyacrylonitrile (PAN) fibres was developed to improve water capture over a wide RH range. Mixed-linker CAU-10 frameworks with different NH₂ ratios were synthesised to adjust hydrophilicity and adsorption performance. Structural analysis confirmed that crystallinity and stability were maintained after incorporating amines and fabricating the membrane. Water adsorption studies revealed that pure CAU-10 adsorbed 452 cm³/g at P/P₀ = 0.8, while amine functionalization increased low-humidity uptake to 69 cm³/g at P/P₀ = 0.1. The best-performing CAU-10-(0.5 NH₂)@PAN membrane combined strong low-pressure adsorption (50 cm³/g) with a high overall capacity (376 cm³/g at P/P₀ = 0.8), proving it to be a durable and efficient MOF–polymer composite suitable for scalable AWH applications.