Heterogeneous photocatalysis is regarded as a sustainable as well as a promising method which has been majorly investigated for different applications. Among them solar fuel production and degradation of organic pollutants have attracted a great deal of research. Graphitic carbon nitride (g-C3N4) has gained immense attention in the field of heterogeneous photocatalysis due its unique physical and chemical properties. For the enhancement of the photocatalytic activity of the graphitic carbon nitride doping by molecules and decorating by bimetallic nanoparticles are found to be suitable approach. To the best of our knowledge surface modification of g-C3N4 by molecule doping followed by decorating with the earth abundant and cheap bimetallic nanoparticles has not been reported yet. Keeping this in mind, this PhD thesis is focused on decoration of non-noble bimetallic nanoparticles over molecule doped g-C3N4. The composite will be used for the photocatalytic degradation of pharmaceutical contaminants like Ibuprofen, Chloramphenicol, Atrazine and hydrogen gas evolution by water splitting and the evolved hydrogen gas will be utilized for the transfer hydrogenation of N-heterocyclic organic substrates. The formation of the nanocomposites will be confirmed by characterization like XRD, FESEM, SEM, EDS with EDS mapping, UV-Vis, and PL. To verify the structure of molecule-doped g-C3N4 solid-state 13C magic angle spinning (MAS) NMR will be used. To know the average oxidation state of the elements in the bimetal, coordination number and bond distance with its neighbouring atoms EXAFS and XANES will be done. N2 adsorption-desorption will be done to achieve structural, morphological information and XPS will be done to know the redox active states of prepared nanocomposite. To quantify the H2 evolution amount GC-MS will be done. And for transfer hydrogenation, characterization techniques like NMR and Mass spectra will be utilised for the identification of the hydrogenated products. The approach documented in this thesis will provide the scope of removal of toxic pharmaceutical contaminants, safe H2 generation and sequential organic transformations via tandem photocatalysis and will provide new insights in use of such materials in photochemical applications.