Solar energy is an abundant renewable source to tackle energy and environmental concerns. For example, solar energy can be converted into electricity, can be used to produce fuels from water and/or CO2 and can be utilised to purify polluted air and water from industrial wastes. These photo-catalytic processes involve a catalyst which plays a crucial role in the efficiency of a process. We study photocatalytic oxidation of organic pollutants, such as phenol, from waste water using a porous TiO2 catalyst. This photo-catalytic process however has low efficiency and produces unwanted by-products which are equally, if not more, harmful than the parent pollutant itself. Therefore, using total neutron scattering, we aim to better understand the local environment of liquids (structure and orientation) within catalyst pores and thereby the reaction mechanism to mitigate unwanted by-products.