Continuous Metal–Organic Framework Biomineralization on Cellulose Nanocrystals: Extrusion of Functional Composite Filaments

Growing metal–organic frameworks (MOFs) around biomolecules has recently emerged as a promising method to combine natural and synthetic materials. In parallel, cellulose nanocrystals (CNCs) have found use for forming a wide range of renewable nano- and macroscopic materials because of their bio-derived nature, high surface area, and high strength. Herein, we demonstrate the continuous nucleation of MOFs from the surface of CNCs, thereby forming hybrid hydrogels, aerogels, and porous assemblies that can be pre- or postloaded with functional cargo. With simple mixing of CNCs with MOF precursors, the biomineralization is initiated and takes place continuously where the MOFs simultaneously coat and cross-link the CNCs across a wide range of CNC and MOF precursor concentrations. Additionally, CNCs can be extruded into the premixed MOF precursors to yield CNC–MOF filaments that can be preloaded with functional enzymes or postloaded with small fluorophores. Overall, our approach enables the rapid structural control of functional composites promising for a range of applications.