Mandy, Margot

Molecular hydrogen is the dominant molecular species present in the interstellar medium and has an important role in the cooling of shocks that are associated with star formation. The two mechanisms of cooling are collisional excitation followed by quadrupole emission and collisional dissociation. Modelling the role of dissociation in this cooling needs detailed information on the state specific dissociation rate coefficients. The initial goal of this research was to compare the trajectory outcomes on the Hinde potential energy surface (PES) with those on the BMKP2 PES to assess whether it is required to do extensive and more expensive calculations to determine state specific rate coefficients for dissociation of H2 + H2 to supersede those previously determined with the BMKP2 surface. A phenomenon of double dissociation was unexpectedly identified within the Hinde PES, despite the absence of sufficient energy for such an occurrence. These results prompted a comprehensive analysis of the Hinde PES, which in turn involved an exploration of the regions that exhibit unphysical behavior. This detailed examination unveiled problematic aspects of the potential energy surface. As a result of this, it has been determined that the Hinde PES is unsuitable for calculating dissociation rate coefficients for H2 + H2.

With the increase in carbon dioxide emissions into the environment, there is an increased need to capture carbon dioxide (CO2). One method of removal of CO2 that has been receiving more attention is its conversion to useful chemicals. Metal organic frameworks (MOFs) are promising candidates in catalysis because of their remarkable properties such as great surface area, high stability, active sites, porosity, tunability and affinity for CO2. In this study metal organic framework i.e., MOF-199, developed by solvothermal and evaporation-induced self-assembly (EISA) techniques, was used to catalyze the reaction between CO2 and epoxides such as propylene oxide (EP1), styrene oxide (EP2), epichlorohydrin (EP3), and 1,2-epoxybutane (EP4). The corresponding carbonates are obtained by using tetrabutylammonium bromide (TBAB) as a co-catalyst. The synthesized MOF-199 was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy, and Brunauer-Emmett-Teller analysis. More than 65% conversion of epoxides (EP1, EP2, EP3, and EP4) to their corresponding carbonates were obtained under mild reaction conditions (100°C and 70 psi) over the synthesized MOF-199 catalysts (1S, 2E, 3E, and 4E), and co-catalyst (TBAB). The percentage yields of cyclic carbonates were determined by using 1H-NMR spectroscopy. The synthesized MOF catalysts demonstrated the high catalytic activity for the chemical fixation of CO2 to cyclic carbonates at mild reaction conditions.

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