Mostafa Yousefzadeh Borzehandani

Agrichemical adjuvants that combine a highly selective, efficient, and active mode of operation are critically needed to realize a more sustainable approach to their usage. Herein, we report the synthesis and full characterization of two new metal-organic frameworks (MOFs), termed UPMOF-1 and UPMOF-2, that were constructed from eco-friendly Ca2+ ions and naturally-occurring, low molecular weight plant acids, L-malic and D-tartaric acid, respectively. Upon structural elucidation of both MOFs, a widely-used fungicide, hexaconazole (Hex), was loaded on the structures reaching binding affinities of -5.0 and -3.5 kcal mol-1 and loading capacities of 63 and 62% for Hex@UPMOF-1 and Hex@UPMOF-2, respectively, as a result of the formation of stable host-guest interactions. Given the MOFs’ framework chemistry and predisposition to disassembly in relevant agricultural conditions, the sustained release kinetics were determined to show near quantitative release (98 and 95% for Hex@UPMOF-1 and Hex@UPMOF-2, respectively) after >500 h – a release profile drastical-ly different than the control (>80% release in 24 h), from which the high efficiency of these new systems was established. To confirm their high selectivity and activity, in vitro and in vivo studies were performed to illustrate the abilities of Hex@UPMOF-1 and Hex@UPMOF-2 to combat the known, aggressive pathogen Ganoderma boninense (G. boninense) that causes basal stem rot disease in oil palm. Accordingly, at an extremely low concentration of 0.05 μg mL-1, both Hex@UPMOF-1 and Hex@UPMOF-2 were demonstrated to completely inhibit (100%) G. boninense growth and during a 26-week in vivo nursery trial, the progression of basal stem rot infection was not only completely halted upon treatment with Hex@UPMOF-1 and Hex@UPMOF-2, but seedling growth accelerated given the additional nutrients supplied via the disassembly of the MOFs. This study represents a significant step forward in designing adjuvants to support the environ-mentally responsible use of agrichemical crop protection.

In this study, the ability of the highly scalable metal-organic framework (MOF) CALF-20 to adsorb polar and non-polar gases at low pressure was investigated using grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The results from the simulated adsorption isotherms revealed that the highest loading was achieved for SO₂ and Cl₂, while the lowest loading was found for F₂ molecules. The analysis of interaction energies indicated that SO₂ molecules were able to form the strongest adsorbent-adsorbate interactions and had a tight molecular packing due to their polarity and angular structure. Additionally, Cl₂ gas was found to be highly adsorbed due to its large van der Waals surface and strong chemical affinity in CALF-20 pores. MD simulations showed that SO₂ and Cl₂ had the lowest mobility inside CALF-20 pores. The values of the Henry coefficient and isosteric heat of adsorption confirmed that CALF-20 could selectively adsorb SO₂ and Cl₂. Based on the results, it was concluded that CALF-20 is a suitable adsorbent for SO₂ and Cl₂ but not for F₂. This research emphasizes the importance of molecular size, geometry, and polarity in determining the suitability of a porous material as an adsorbent for specific adsorbates.

For the first time, metal-organic framework NUIG2 has been investigated for the adsorption and separation of methane (C1), ethane (C2), propane (C3) and butane (C4) at low pressure. In order to calculate the loading and mobility of the gas molecules inside NUIG2, grand canonical Monte Carlo and molecular dynamics simulations were performed. C2 and C3 had the maximum loading on the framework because of their appropriate molecular size and tightly fitting into the pores. On the other hand, C1 molecules were able to be freely situated in all pores, but C4 molecules were accommodated only into the largest channels. Radial distribution function analysis revealed that methyl and phenyl groups of the framework were the most favorable sites for hydrophobic interaction with the gas molecules. The Henry coefficient indicated that the adsorption affinity of the gas molecules into the NUIG2’s pores was in the order of C1 < C2 < C3 < C4 following molecular size. The diffusion of C1 molecules were significantly fast, while its loading was high in the framework. However, C3 and C4 molecules did not demonstrate any diffusion at any loading. Overall, we have concluded that NUIG2 is desirable for the adsorption of C2 and C3, whereas is beneficial for the selectivity of C4 over C1 molecules. NUIG2 is expected to be a very promising MOF for further study into the adsorption and separation of alternative gases.

Covalent organic frameworks (COFs) have a distinguished surface as they are mostly made by boron, carbon, nitrogen and oxygen. Many applications of COFs rely on polarity, size, charge, stability and hydrophobicity/hydrophilicity of their surface. In this study, two frequently used COFs sheets, COF-1 and covalent triazine-based frameworks (CTF-1), are studied. In addition, a theoretical porous graphene (TPG) was included for comparison purposes. The three solid sheets were investigated for aromaticity and stability using quantum mechanics calculations and their ability for water and ethanol adsorption using molecular dynamics simulations. COF-1 demonstrated the poorest aromatic character due to the highest energy delocalization interaction between B–O bonding orbital of sigma type and unfilled valence-shell nonbonding of boron. CTF-1 was identified as the least kinetically stable and the most chemically reactive. Both COF-1 and CTF-1 showed good surface properties for selective adsorption of water via hydrogen bonding and electrostatic interactions. Among the three sheets, TPG’s surface was mostly affected by aromatic currents and localized π electrons on the phenyl rings which in turn made it the best platform for selective adsorption of ethanol via van der Waals interactions. These results can serve as guidelines for future studies on solvent adsorption for COFs materials.