Tunable porous materials for targeted pest control Joshua Nicks, Greig C. Shearer, Joe Paul-Taylor, Tina Düren, Andrew D. Burrows University of Bath, UK Global food security is one of the main issues facing modern society and is among the UN’s long-term sustainable development goals. A key aim in solving this problem is the design of improved pesticide management strategies, as current methods require large volumes of pesticide, can affect non-pest species, and can contaminate the crop. Lure traps are a potential alternative, utilizing semiochemicals (or pheromones) to attract the pest to a pesticide- laden bait. However, the shelf life of these traps is relatively short, as these semiochemicals are highly volatile and evaporate quickly in field conditions. Our work focuses on the use of a class of porous materials called metal-organic frameworks (MOFs) to adsorb these semiochemicals, with the aim of manipulating their release rate based on the MOFs pore structure. MOFs were chosen as their modular structures, composed of metal nodes and organic linker struts, can be modified both pre- and post-synthetically to tune their pore environments. 1 Initial work focussed on the IRMOF and IRMOF-NH 2 structures, and alkyl-chain functionalised derivatives of the latter. 2 These results showed that introduction of a hydrogen-bond donor amine increased semiochemical retention, which is further enhanced by introduction of alkyl chains, regardless of their reduced surface areas. This resulted in a more controlled and prolonged release of the semiochemicals over months rather than weeks. Field trials then showed that leaf-cutter ants, Atta sexdens , exhibit enhanced attraction to both semiochemical-laden and MOF-laden bait, with no observable difference in behavior between the two. This work seeks to further establish how the pore structure of a MOF can be used to tune and control the release rate of various semiochemicals. In this study, a series of channel-type MOFs with increasing pore sizes and pore shapes was examined for the uptake and release of isobutyl acetate, an attractant for fruit flies, Drosophila melanogaster . The chosen structures use highly stable Zr(IV) and Al(III)-based frameworks, for suitability in field conditions, and loaded through a vapour diffusion method designed to maximise uptake. It was found that pore size and shape both have a direct effect on the initial uptake, and subsequent release of the semiochemical, with smaller pores adsorbing less and releasing slower, in contrast to the high uptake and faster release of larger pores. These results indicate that it is possible to tune the rate of isobutyl acetate release by tunning the pores of MOFs. Thus, it appears MOF semiochemical adsorption has great potential in novel pesticide management, with further field trials and other semiochemical studies underway. References 1. H. Furukawa, K. E. Cordova, M. O'Keeffe, O. M. Yaghi, Science, 341, 1230444. 2. Amer Hamzah, D. Rixson, J. Paul-Taylor, H. V. Doan, C. Dadswell, G. W. Roffe, A. Sridhar, C. L. Hobday, C. Wedd, T. Düren, W. O. H. Hughes, J. Spencer and A. D. Burrows, Dalton Trans. , 2020, 49 , 10334–10338.
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