Preparation of Cationic MOFs with Mobile Anions by Anion Stripping to Remove 2,4-D from Water

Metal-Organic Frameworks as Potential Agents for Extraction and Delivery of Pesticides and Agrochemicals

Pesticide contamination is a global issue, affecting nearly 44% of the global farming population, and disproportionately affecting farmers and agricultural workers in developing countries. Despite this, global pesticide usage is on the rise, with the growing demand of global food production with increasing population. Different types of porous materials, such as carbon and zeolites, have been explored for the remediation of pesticides from the environment. However, there are some limitations with these materials, especially due to lack of functional groups and relatively modest surface areas. In this regard, metal-organic frameworks (MOFs) provide us with a better alternative to conventionally used porous materials due to their versatile and highly porous structure. Recently, a number of MOFs have been studied for the extraction of pesticides from the environment as well as for targeted and controlled release of agrochemicals. Different types of pesticides and conditions have been investigated, and MOFs have proved their potential in agricultural applications. In this review, the latest studies on delivery and extraction of pesticides using MOFs are systematically reviewed, along with some recent studies on greener ways of pest control through the slow release of chemical compounds from MOF composites. Finally, we present our insights into the key issues concerning the development and translational applications of using MOFs for targeted delivery and pesticide control.

In situ remediation of 2,4-dicholrophenoxyacetic acid herbicide using amine-functionalized imidazole coordination complexes

Demand of clean water is always a major concern due to continuous use of toxic pesticides and herbicides to overcome food scarcity. In Asian countries, wide use of ionizable 2,4-D herbicide has worsen problem due to its less binding ability with soil and can easily contaminate drinking water that causes potential risks to humans and environment. The present research focused on synthesis of amino-factionalized coordination complexes using imidazole-based amino benzoic acid ligands for remediation of acidic 2,4-D herbicide. Coordination complexes characterized with FTIR, ¹H-NMR, elemental analysis, thermogravimetric analysis, powder XRD, and BET revealed successful incorporation of functionalized groups with high thermal stability and surface area that make them suitable for adsorption experiments. Batch adsorption experiments conducted at different temperature conditions depicted the spontaneous physisorption process (- ∆G) having endothermic nature (∆H, ∆S). The removal efficiency of the amino-functionalized coordination complex is found to be higher (73%) compared to non-functionalized (35%) and acetic anhydride-functionalized coordination complex (42%). Kinetic studies supported pseudo 2nd-order kinetics with three phases of adsorption depicted by intra-particle diffusion model. Amino-functionalized complexes favored Langmuir isotherm while Freundlich isotherm is best fitted for non-functionalized complexes. The synthesized adsorbents were also proven to be effective for removal of herbicide from irrigated wastewater with average percent removal of 56% for amino functionalized, acetic anhydride functionalized (23%), and non-functionalized (20%).

Preparation of UiO-66-NH2 and UiO-66-NH2/sponge for adsorption of 2,4-dichlorophenoxyacetic acid in water

MOFs are usually used as efficient adsorbents to remove specific pollutants in water. However, because of their poor water stability relatively small particle size, their application in adsorbing and removing pollutants from water is limited. In this paper, with nitrile rubber sponge as the substrate, UiO-66-NH₂/sponge composites were firstly in-situ synthesized and systematically evaluated UiO-66-NH₂ as an adsorbent to remove 2,4-dichlorophenoxyacetic acid from water. This composite could not only remain the adsorption capacity for 2,4-dichlorophenoxyacetic acid of UiO-66-NH₂, but also was much more convenient for separation after the adsorption compared to UiO-66-NH₂. In addition, the mechanism of the adsorption of UiO-66-NH₂ for 2,4-dichlorophenoxyacetic acid were discussed in detail. Electrostatic interaction between UiO-66-NH₂ and 2,4-dichlorophenoxyacetic acid was the main adsorption mechanism. The adsorption was mainly suitable for Langmuir isotherm models, and its maximum adsorption capacity of 2,4-dichlorophenoxyacetic acid was 72.99 mg g^-1.