Development of efficient and robust organic-based systems for light-driven hydrogen evolution is crucial to the progression of cost-effective green hydrogen production as an alternative to the burning of fossil fuels. Conjugated organic polymers offer potential for advancement in this area mainly fuelled by their tunability, low-cost and availability of starting materials. The main objective this research was to incorporate boron-dipyrromethene (BODIPY) chromophores into a polymeric backbone and investigate the activity of a series of BODIPY polymers for hydrogen generation. Although extensive research has been carried out on inorganic complexes for hydrogen evolution, many studies utilise ultraviolet (UV) light to drive these reactions and their activity using visible light is very poor. This project aims to surmount this limitation in the development of BODIPY polymers that absorb in the visible region of the solar spectrum. Furthermore, existing research on inorganic photocatalysts require the use of expensive and rare metals in their overall synthesis – the polymers reported in this project are comprised of fully organic-based molecular architectures and their activity for hydrogen evolution was studied in conjugation with an earthabundant cobalt-based molecular catalyst. The novel BODIPY polymers were characterised using 1H, 13C NMR spectroscopy, gel permeation chromatography, UVvisible absorption, and photoluminescence spectroscopy. Little is known about the mechanism of polymeric photocatalysts and their activity that leads to enhancement in hydrogen evolution. The experimental work presented here provides one of the first investigations into the photodynamic properties of the polymers in solution-based studies. This was carried out using both transient absorption (TA) and time-resolved infrared (TRIR) spectroscopies spanning the early picosecond (ps) to microsecond (s) timescale, including measurement of a triplet-state lifetime (s timescale), which is an important photophysical property of the polymer required to advance the efficiency of the system. Although this study focuses on the novel BODIPY polymers for hydrogen evolution, the findings were hypothesised to have bearing on antimicrobial applications as they possess the desired properties of a successful photodynamic therapy (PDT) agent (i.e. long-lived triplet lifetime and absorptivity in the visible region of the spectrum). Hence, the copolymers were also assessed for their ability to generate singlet oxygen lv as a potential for use in antimicrobial applications and were successful both in solution and when absorbed onto a surface for killing both gram-negative and gram-positive bacteria. Inorganic complexes are well established in the field of photocatalytic hydrogen evolution. Their activity for hydrogen evolution, combined with their superior photostability make them ideal candidates for viable scale-up options. However, poor absorptivity in the visible light region of the solar spectrum has limited the application of inorganic complexes such as ruthenium(II) polypyridyl complexes. A main objective of the research on novel Ru(II) complexes in this thesis was to extend the visible light absorptivity of these inorganic complexes through -extended ligands and addition of ligands with different donor strengths. The investigation of the photophysics of these complexes is imperative to gain an understanding of the excited state dynamics and hence optimise these complexes for solar-driven applications.