High-strength and transparent iron-based MOFs@nanocellulose composite film: a novel material for effective UV to high energy blue light shielding

Our eyes and skin are frequently exposed to harmful ultraviolet (UV) and high-energy blue light (HEBL) radiation from sunlight and modern IT devices. Although many efforts have been made to develop UV-shielding film materials, it is very challenging to extend the shielding area to harmful HEBL. In this study, iron-based metal–organic frameworks with strong light absorption were grown on TEMPO-oxidized cellulose nanofibers (TOCNFs) at room temperature using an in situ green synthesis method, yielding multifunctional MIL-101(Fe)@nanocellulose composite films (M(Fe)TOCNFs). Based on the excellent light absorption capacity of MIL-101(Fe), M(Fe)TOCNFs exhibit UV and HEBL double shielding performance. M(Fe)TOCNFs can block 99.8–100% UV light and 82.4–97.8% HEBL while maintaining high transmittance (68.9–79.7% at 600 nm). Encouragingly, M(Fe)TOCNFs can effectively block the HEBL emitted by white light emitting diode (WLED) in computer and mobile phone screens as well as UV rays from sunlight. Moreover, the water contact angle of M(Fe)TOCNFs increased from 47.3° to 68.2° with the addition of MIL-101(Fe). Remarkably, MIL-101(Fe) can significantly improve the flame retardancy of M(Fe)TOCNFs. Although the incorporation of MIL-101(Fe) reduced the tensile strength of the composite films, but it remained above 109 MPa, surpassing the mechanical strength of most plastic films. The synthesis of M(Fe)TOCNFs is simple, green, efficient and low-cost with good transparency and flame retardant properties, making it suitable for use as a protective coating against sunlight and harmful emissions from IT devices.