Zirconium-based MOFs and their biodegradable polymer composites for controlled and sustainable delivery of herbicides Sanjit Nayak 1 , Lila A. M. Mahmoud 1,2 , Richard Telford 1 , Tayah Livesey 1 , Maria Katsikogianni 1 , Adrian Kelly 3 , Lui R. Terry, 4 Valeska P. Ting 1 1 University of Bradford, School of Chemistry, UK, 2 School of Pharmacy, Al-Zaytoonah University of Jordan, Jordan, Polymer IRC, 3 Faculty of Engineering and Informatics, University of Bradford, UK, 4 Bristol Composites Institute, Department of Mechanical Engineering, University of Bristol, UK Contamination of ground water and soil from agrochemicals is a major contributor to ecotoxicity. 12, For example, large proportion of pesticides used in farming industry miss the target vegetation and contaminates the environment. 3 Many of these pesticides are linked to different diseases including cancer. In recent years, adsorption and controlled release of agrochemicals have been studied widely using different nanomaterials and a variety of formulations. However, the potential for application of high surface-area metal–organic frameworks (MOFs) for the controlled release of agrochemicals has not been much explored yet. 4 Herein, we investigated the possible application of a composite membrane for contact-based delivery of herbicides, assisted by rainwater or other sources of water (Scheme 1). Controlled and sustainable release of a widely used herbicide (2-methyl- 4-chlorophenoxyacetic acid, MCPA) loaded into a range of zirconium-based MOFs and their biodegradable polymer composites was studied in detail. 5 Three Zr-based MOFs, viz., UiO-66, UiO-66-NH 2 , and UiO-67 were loaded with MCPA either post-synthetically or in situ during synthesis of the MOFs. The MCPA-loaded MOFs were then incorporated into a biodegradable polycaprolactone (PCL) composite membrane. All three MOFs and their PCL composites were thoroughly characterized using FT-IR, TGA, SEM, PXRD, BET, and mass spectrometry. Release of MCPA from each of these MOFs and their PCL composites was then studied in both distilled water and in ethanol for up to 72 h using HPLC. The best performance for MCPA release was observed for the post- synthetically loaded MOFs, with PS-MCPA@UiO-66-NH 2 showing the highest MCPA concentrations in ethanol and water of 0.056 and 0.037 mg/mL, respectively. Enhanced release of MCPA was observed in distilled water when the MOFs were incorporated in PCL. The concentrations of herbicides in the release studies provide us with a range of inhibitory concentrations that can be utilized depending on the crop, making this class of composite materials a promising new route for future agricultural applications.
References 1. Bai, S. H.; Ogbourne, S. M., Sci. Pollut. Res . 2016, 23, 18988– 19001. 2. Nicolopoulou-Stamati, P.; Maipas, S.; Kotampasi, C.; Stamatis, P.; Hens, L., Public Health 2016, 4, 8. 3. Van den Berg, F.; Kubiak, R.; Benjey, W. G.; Majewski, M.; Yates, Sr.; Reeves, G. L.; Smelt, J.; van der Linden, A, Water, Air, Soil Pollut. 1999, 115, 195– 218. 4. Mahmoud, L. A. M., Reis, R., Chen, X, Ting, V. P., and Nayak, S. , , ACS Omega , 2022, 7, 45910-45934. 5. Mahmoud, L. A. M., Telford, , Livesey, T., Katsikogianni, M., Kelly, A., Terry, L, Ting,V. P., and Nayak, S., ACS Appl. Bio Mater . 2022, 5, 8, 3972–3981.
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