ABSTRACTHere is reported the synthesis of o-phenylenediamine functionalized graphite (OPDFG) using the phosphorus trichloride surface modified graphite (PCl3-SMG) and the o-phenylenediamine (OPD). PCl3-SMG was obtained via chlorophosphorylation of graphite for the study. PCl3-SMG and OPDFG were analyzed using ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). UV-Vis analysis shows that OPDFG have higher absorbance than graphite and PCl3-SMG. According to FTIR analysis, PCl3-SMG has –PCl2 functional groups, which shows that PCl3 reacts with sp2 C-H groups on graphite's edge planes during the formation of PCl3-SMG. Synthesis of OPDFG can be explained by a replacement reaction of amine groups of OPD with –PCl2 groups. XRD data show that after modification of graphite with PCl3 and after amine treatment of PCl3-SMG, crystallite sizes of PCl3-SMG and OPDFG decrease. SEM analysis shows that both PCl3-SMG and OPDFG have layered structures similar to graphite.