In this thesis, we focus is on the investigation of charge carrier dynamics in carbon nitride materials (PCNs) on time scales ranging from femtoseconds to microseconds by transient absorption and time-resolved emission spectroscopy. This work aims to tackle the major problems that limit the photocatalytic performance of bare PCNs, i.e., insufficient visible-light absorption, rapid charge carrier recombination, low specific surface area and poor dispersion in solvents. Therefore, three carbon nitride examples (R-CNx, {Mo3}-CNx, and K,Na-PHI) are introduced to extend our understanding in four directions:1) the impact of azo-moieties formed after high-temperature heat treatment on charge carrier dynamics; 2) charge carrier dynamics upon the incorporation of cocatalyst; 3) the interplay between surface functional groups and charge carrier dynamics; 4) the variation of charge carrier dynamics in the presence of chemical quenchers
