Polysaccharides are attractive sustainable resources for the fabrication of advanced materials, but the assembly of these building blocks into complex-shaped structures combining the high strength and low weight required in many applications remains challenging. We have investigated and optimized the rheological and mechanical properties of polysaccharide-based composite foams based on mixtures of methylcellulose (MC), cellulose nanofibrils (CNF), montmorillonite (MMT), and glyoxal and tannic acid. Such foams were found to be stabilized by the coadsorption of MC, CNF, and MMT at the air-water interface, while the complexation of the polysaccharides with tannic acid improved the foam stability. Tannic acid could also be used to tune and optimize the microstructure and the viscoelastic properties of the wet foam for direct ink writing of robust cellular architectures. Glyoxal had no noticeable effect on the properties of the wet foams but significantly enhanced the water resilience and stiffness of the lightweight material obtained after drying at ambient pressure and elevated temperatures with minimum shrinkage. The foams possessed a high porosity and displayed a specific Youngs modulus and yield strength that outperformed other biobased foams and commercially available expanded polystyrene. The strong and water-resilient 3D printed foams can be surface modified using, for example, aminosilanes, which opens up applications for air purification and thermal insulation.

Organosilica foams are commonly formed by a multistep process involving hydrolysis and condensationof organosilanes followed by solvent exchange and e.g. supercritical CO2 drying. Here, we propose astraightforward route to synthesize lightweight hybrid foams from aqueous dispersions of a surfaceactiveaminosilane (AS) and TEMPO-oxidized cellulose nanofibrils (TCNFs). Air bubbles were introducedin the TCNF/AS dispersion by mechanical blending, and the foam was solidified by oven-drying.Evaporative drying at mild temperature (60 1C) resulted in dry foams with low densities (25–50 kg m3),high porosities (96–99%) and macropores of 150–300 mm in diameter. The foaming and foam stabilizationwere successful for a pH range of 10.4–10.8 for foams containing 55–65 wt% of organosilica inthe dry state. The protonation of AS increased the ionic strength of the dispersion and enhanced theinterparticle interactions with TCNFs and, in turn, the foam viscosity and foam stability upon drying. Theevaporation of water catalyzed the condensation of the AS to form low-molecular linear polymers,which resulted in an increased stiffness and strength of the foam lamella. The crosslinking of the ASpolymeric network with the TCNF matrix allowed lightweight and homogeneous macroporous foams tobe obtained with controlled densities and high amine content (amine content 44.5 mmol g1) using anenvironmentally friendly technique.

Nanocellulose is a renewable material that combines a high surface area with high strength, chemical inertness, and versatile surface chemistry. In this review, we will briefly describe how nanocellulose is produced, and present-in particular, how nanocellulose and its surface modified versions affects the adsorption behavior of important water pollutants, e.g., heavy metal species, dyes, microbes, and organic molecules. The processing of nanocellulose-based membranes and filters for water purification will be described in detail, and the uptake capacity, selectivity, and removal efficiency will also be discussed. The processing and performance of nanocellulose-based membranes, which combine a high removal efficiency with anti-fouling properties, will be highlighted.