Lignocellulosic Biomass as a Sustainable Substrate for Robust Fabrication of Metal-Organic Frameworks (MOFs)

The applicability of various polymer substrates to conjugate metal-organic frameworks (MOF) is mostly limited owing to inferior mechanical properties and the high costs of synthetic polymers. Additionally, the use of synthetic polymer substrates and solution phase synthesis of MOF to fabricate MOF/fiber composites present several drawbacks, including agglomeration of MOF particles, time-intensive fiber making process, reduced MOF functionality after its incorporation and large consumption of organic solvents. Herein, we report a sustainable approach to integrate MOF via vapor phase synthesis, on a cost-effective and mechanically strong lignocellulosic fibrous banana paper (BP) substrate developed from the biomass of banana harvest. Uniform and conformal metal oxide is deposited on the substrate through atomic layer deposition (ALD), followed by exposure to the organic linker. We systematically investigate the effect of the amount and conversion time of the metal oxide on the MOF growth. The resultant MOF-BP composites demonstrate a high surface area of 552 m²/g. Uniform surface growth of MOF via the vapor phase approach and a hierarchical porous structure of the BP facilitate gas diffusion properties of MOF, while the mechanical strength of the substrate is well retained after the MOF growth. We have investigated the full accessibility of MOFs on the fibrous substrate via CO₂ adsorption. Additionally, enhanced antibacterial properties of the BP-MOF composites are verified via antibacterial contact assays, while preliminary studies indicate a promising sorption profile of volatile organic compounds. We believe that the sustainable nature of the lignocellulosic BP substrate and uniform growth of MOF on the hierarchical porous structure impart impressive attributes to these composites which can be explored in diverse applications ranging from antibacterial packagings to sensors.