Desarrollo de redes metalorgánicas para aplicaciones medioambientales

Abstract

One of the greatest challenges of the 21st century is to increase the crop production to supply the high food demand of the ever-growing global population. Inevitably, this challenge has led to a rise in the agrochemical use, mainly fertilizers and pesticides, in order to maximize agricultural crop yields. However, the indiscriminate use of these agrochemicals has deteriorated the quality of aquatic and terrestrial ecosystems and it is even harmful to human health. Chemical fertilizers are composed mostly by nitrogen and phosphorous. Nevertheless, unlike nitrogen, phosphorous is a non-renewable source extracted mainly from mineral apatite. As a consequence of the indiscriminate use of this finite source, the maximum peak of phosphate rock is expected to be reached between 2030- 2100. While 90 % of mined phosphate rock is used for fertilizer production, only onefifth of it reaches the global food chain, with the major leaching into soil or aquatic media leading serious environmental problems (e. g. eutrophication). On the other hand, among the different types of pesticides on the market, organophosphorus pesticides (OPs) are the most widely used (45 % of the world market). However, the abusive use of pesticides has led to bioaccumulation in the environment, with concentrations that exceed the legal limits causing a harmful effect on health. In particular, these organophosphorus compounds are highly toxic (responsible for 110 000 deaths per year) because they affect the central nervous system by inhibiting the acethylcholinesterase (AchE) enzyme. In this context, detoxification measures need to be developed and implemented, such as: (i) adsorption processes of toxic pesticides; (ii) degradation of pesticides to harmless chemicals; and/or (iii) treatment with AChE enzyme reactivators (e.g. oximes). In this context, this PhD Thesis aims to provide new studies on the use of metalorganic frameworks (MOFs) and hybrid materials based on them, as phosphorus detoxification and/or recovery systems. MOFs are crystalline porous materials, which have a high surface area and are easily functionalised. Among the wide variety of MOFs described in literature, Zr-based metal-organic frameworks are of great interest, due to the low toxicity of Zr metal, their elevated chemical stability and high affinity for phosphorus compounds. Moreover, these porous systems have been shown to be effective in the hydrolysis of organophosphorus compounds due to the combination of Lewis acid cations (Zr4+) and basic groups (O/OH-) in their structures.