Synthesis of polycyclic aromatic hydrocarbons within the nanocages of LTA zeolite using methanol as the reactant

Abstract

Polycyclic aromatic hydrocarbons (PAHs) have an $sp^2$-hybridized backbone composed of multiple aromatic rings. They exhibit fluorescence often in the visible region and high electric conductivity, attractive for various applications. Recently, our group has developed a novel synthesis strategy for PAHs using the nanocages of LTA zeolite as nanoscale reactors and acetylene as the reactant. In this thesis, methanol was utilized as an alternative reactant for the LTA zeolite-mediated PAH synthesis. Compared to acetylene, methanol was expected to provide a novel atom-by-atom carbon addition pathway towards PAH growth, leading to the generation of high-mass curved PAHs along the LTA zeolite pore surface. The methanol-based products exhibited significantly enhanced fluorescence emission in the green-orange range, indicating the formation of high-mass PAHs. The MALDI-TOF mass spectrum of the PAHs further enforced this showing peaks over 600 amu. With the PAH of 398 amu ($C_{30}H_{14}$, ovalene) being theoretically the largest planar PAH that can fit in the LTA zeolite supercage, these highmass PAHs were anticipated to adapt a curved structure. Finally, the single-atom addition pathway towards PAH growth was confirmed through the 14 amu intervals (i.e. $CH_2$ unit) between the peaks within the MALDI-TOF mass spectrum of the resultant product.