Highly Transparent, Flexible, and Mechanically Strong Nanopapers of Cellulose Nanofibers @Metal–Organic Frameworks

Freestanding nanopapers were fabricated by the assembly of metal–organic frameworks (MOFs) onto cellulose nanofibers (CNFs). The CNFs are wrapped by continuously nucleated MOF layers (CNF@MOF) by interfacial synthesis, with the charge density on the surface of the CNFs and the dosage of the surfactant polyvinylpyrrolidone (PVP) being carefully adjusted. The obtained CNF@MOF nanofibers with long‐range, continuous, hybrid nanostructures were very different to the composites formed by aggregation of MOF nanoparticles on the substrates. Four typical MOFs (HKUST‐1, Al‐MIL‐53, Zn‐MOF‐74, ZIF‐CO 3 ‐1) were successfully grown onto CNFs in aqueous solutions and further fabricated into freestanding nanopapers. Because of their unique nanostructures and morphologies, the corresponding flexible nanopapers exhibit hierarchical meso ‐micropores, high optical transparency, high thermal stability, and high mechanical strength. A proof‐of‐concept study shows that the CNF@MOF nanopapers can be used as efficient filters to separate volatile organic compounds (VOCs) from the air. This work provides a new path for structuring MOF materials that may boost their practical application.