A Sustainable One-Pot Preparation Method for Very High Porous Solids Loading Paper Membranes

Owing to their high porosity and tunability, porous solids such as Metal-Organic Frameworks (MOFs), Zeolites and Activated Carbons (ACs) are of great interest in various fields for instance gas separation, catalysis, water and air purification, among others. These materials are usually in powder form and need to be shaped in some practical way that does not modify their intrinsic property (i.e. porosity). Making porous, freestanding and flexible membranes is a shaping strategy. However, high loadings (> 70 wt %) can challenge mechanical properties. We have developed a new sustainable and simple method that combines two cellulosic fibrous structures of different size to form a high porous solids loading (>70 wt %) paper membrane: softwood bleached kraft fibres (S) and nano-fibrillated cellulose (NFC). This dual fiber system produces a synergistic effect, where S provides flexibility while NFC acts as a nanostructuring and mechanical strengthening agent with an optimal S:NFC=1:2 ratio. This method can be applied for the preparation of membranes with the mechanical properties of paper and unhampered adsorption properties with a wide range of porous solids (MOFs, ACs, Zeolites). As a first application example, the capture of volatile organic compounds is demonstrated with MIL-100(Fe) paper membrane, an iron trimesate MOF