Due to continuous global energy demand and industrial development, considerable interest has been attended towards the health impacts of organic and inorganic pollutants in the environment. Such pollutants can severely damage our aquatic environment. The contamination level increases rapidly every year due to human activities, industrial development and lack of efficient water treatment technology. So far, several studies have shown the presence of organic pollutants in treated water. Meanwhile, some other studies focused on the possible pathways for those pollutants to reach freshwater in the environment. Emerging pollutants can be found in the environment at µg/L to ng/L levels. In general, this includes chemicals such as pharmaceutical compounds and personal care products, as well as endocrinedisrupting chemicals. Moreover, the presence of some pharmaceutical compounds is known for causing a serious effect on the health of living organisms along with the formation of the drug's resistant bacteria. Therefore, it is necessary to design and synthesize of artificial photocatalysts with high activities. Implementation of photocatalytic properties of semiconductor materials has shown potential method to purify wastewaters. This includes materials like metal oxides, metal sulphides and oxygen nitrides. Recently, carbon based materials like graphitic carbon nitride (g-C3N4) is found to show promising photocatalytic properties due to conduction of higher electrical charges, suitable redox potential, band structure located in the visible light region (band gap 2.7 eV), thermal and chemical stability, and the simplicity of production that allows it for large-scale production from low-cost precursors. However, the photocatalytic efficiency of the pure g-C3N4 is limited by the high recombination rate of the photo-induced electron-hole pairs. The aim of this thesis is to design and fabricate pure and modified carbon nitride photocatalytical materials by direct thermal heating and microwave assisted technique and to study the photocatalytic degradation of pharmaceuticals under visible light irradiation. First, several nitrogen-rich precursors were used to prepare carbon nitride materials and after a thorough systematic analysis, few precursors were chosen and studied for large scale, economic and safe production. The synthesized materials were characterized for structure, morphology, surface area, optical and electrochemical properties. The properties were compared with reported results and their variations are interpreted. The photocatalytic efficiency of the synthesized materials were studied for degradation of pharmaceutical residues. The results reveal that the g-C3N4 sample prepared from melamine gives higher yield and photocatalytic efficiency, which has been justified by suitable degradation mechanism. After obtaining the g-C3N4 bulk materials, a thermal oxidation process has been used to produce the g-C3N4 nanosheets. Two heating steps method were operated on the g-C3N4 bulk. The bulk g-C3N4 materials were converted to nanosheets by two thermal oxidation processes operated in a semi-closed system under ambient pressure. The transformation of the bulk materials to nanosheets was confirmed by scanning vii electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), Fourier-transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Bruneaur Emmett Teller (BET) and particle size analysis. The photocatalytic degradation of pharmaceuticals by the nanosheet samples were found to be much faster than the bulk materials. The g-C3N4 nanosheets were coupled with CdS and BiOCl nanoparticles by using microwave-assisted method to obtain rapidly uniform sized CdS/g-C3N4 and BiOCl/g-C3N4 heterojunction nanosheets. The composites were studied by using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), photoluminescence (PL), Lifetime decay measurement, and photocurrent. The photocatalytic degradations of pharmaceuticals by the synthesized materials were studied. Moreover, a direct thermal method is used to couple Graphene (Gr) nanosheet with g-C3N4 nanosheet and characterized by using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Photoluminescence (PL), Lifetime decay measurement, and photocurrent. The prepared samples were tested for photocatalytic degradation of pharmaceutical pollutants. The results in this thesis clearly confirm that the photocatalytic activity of modified carbon nitride (g-C3N4) based materials can efficiently be enhanced by converting the bulk material to nanosheeet and coupling with CdS, BiOCl nanoparticles and graphene nanosheet. The increase in photocatalytic activity can be described due to separation of the photo-induced electron-hole pairs and the increase of the active sites for the photocatalytic reaction. The study further shows that the modified samples can be used to treat wastewater contaminated by pharmaceuticals under visible and solar irradiation