A Green One-Pot Preparation Method for Very High Porous Solids Loading Paper Composites

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 sheets is a relevant shaping strategy. However, achieving high loadings (> 70 wt %) can challenge mechanical properties. We have developed a new green and simple method that combines two cellulosic fibrous structures of different size, i.e. softwood bleached kraft fibres (S) and nano-fibrillated cellulose (NFC), to form a high porous solids loading (>70 wt %) paper sheet. 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=25:75 ratio. This method can be applied for the preparation of sheets exhibiting the mechanical properties of paper while keeping the adsorption properties of a wide range of porous solids (MOFs, ACs, Zeolites). As an exemple of application, a MOF paper has been considered for the capture of polar volatile organic compounds, showing better performance than other shaping processes such as beads and granules.