Azo-Based Porous-Organic Polymers for Energy Storage and Selective Gas Adsorption

The main subject of this Thesis is the examination and exploration of the synthesis and application of azo-connected porous organic polymer materials for sodium-ion batteries and selective gas adsorption. The application of these materials in the literature is scarce, despite promising results.

Chapter Three discussed the synthesis and SIB application of a new azo-connected porous organic polymer, VAP-1. This chapter detailed the full characterisation of VAP-1, comparing experimental and computational results to determine the material’s composition. VAP-1 was then applied as an SIB, and ex situ Raman spectroscopy was used to probe the charging and discharging mechanism. VAP-1 had a internal surface area of 225 (± 5) m2/g, and a bimodal pore distribution with pores having diameters of 8.2 and 10.2 Å. VAP-1 was successfully incorporated into a composite cathode material with a specific capacity of 123 mAh/g in a sodium-coin half-cell, although the composite material could undergo only 30 charge/discharge cycles before it could no longer hold a charge.

Chapter Four explored the further synthesis of three new azo-POPs: VAP-2, VAP-3, and VAP-4. These materials were designed to have analogous compositions to VAP-1 and were characterised using similar methods. The pore size of these azo-POPs was varied in order to probe the effect that changing pore size had on the stability of azo-POP-based electrodes. VAP-2 and VAP-3 had internal surface areas of 42.6 and 28.1 m2/g respectively. Both materials were shown to have PSDs ranging from 10 -14 Å. VAP-3 was assembled into a sodium-coin half-cell and the battery performance was compared to VAP-1. VAP-3 had an experimental capacity of 100 mAh/g over 100 cycles.

Chapter Five demonstrated the selective gas adsorption properties of VAP-1. The gas storage capacities of H2, CO2, C2H6, C2H4, C3H8, and C3H6 were found and showed no clear trend regarding storage capacity. VAP-1 had the highest storage capacity for C3H8 with a wt% of 10.99% C3H8 to VAP-1 and volumetric storage of 59.1 cm3/g at 273 K. The selective gas adsorption for 10 systems was screened using IAST determined from a two-point Clausius Clapeyron equation for each gas tested. The highest gas selectivities within VAP-1 were in the C3H8:C2H4 gas systems with selectivities ranging from 7.96 to 18.96, C3H8:CO2 gas systems with selectivities ranging from 7.52 to 30.12, and the C3H6:CO2 gas systems with selectivities ranging from 8.86 to 26.6. These gas selectivity simulations indicate that VAP-1 may be useful in separating flue gas mixtures containing short-chain hydrocarbons from CO2.

Chapter Six showed the attempted synthesis of an azodioxy-connected COF. Synthetic attempts towards a 2D hcb azodioxy COF and two 3D acs azodioxy COFs were screened. Several new molecules were synthesised including a trigonal prismatic bromine decorated scaffold, 2,3,6,7,12,13-hexa(4-bromophenyl)triptycene, a trigonal prismatic nitroso decorated molecule, 2,3,6,7,12,13-hexanitrosotriptycene. Traditional chemical and electro-organic synthesis were tried, but ultimately failed due to instability of monomers, sterics, electronics, insolubility, and scale.