This work presents the hydrothermal synthesis and characterization of cerium phthalate coordination polymer, Ce-Phth CP, from the inorganic precursor cerium sulphate and the organic linker phthalic acid. Characterization of Ce-Phth CP by SEM/EDX, XRD, and FTIR analyses show that Ce-Phth CP particles are made of rectangular bundled straws of micrometre dimension and can be categorized as crystalline material with some amorphousness. FTIR analysis demonstrates successful coordination of Ce(IV) with phthalate via the Ce–O bond. Ce-Phth CP was applied successfully for advanced oxidation processes (AOP) to degrade the stable azo dye methyl orange (MO) via the Ce-Phth CP/H2O2 heterogeneous catalysis system where the effect of initial pH (2, 7, 10), MO initial concentration (10, 20, 30 ppm) and Ce-Phth CP dosage (50, 100, 200 mg) were studied. Results show that H2O2 best decomposes at pH 10 (about 89% decomposition), while MO best degrades at pH 7 (about 98% degradation). pHPZC of Ce-Phth CP was determined as pH 7.4 which has shown a significant effect on the whole process, decomposition and degradation. Adsorption natures of both H2O2 and MO onto the Ce-Phth CP surface are suggested to be the reason behind the difference in this pH profile of H2O2 decomposition and MO degradation·H2O2 decomposition is shown to follow a regular second-order rate equation, while MO degradation follows the usual pseudo-first-order rate equation. For a selected conditions, Ce-Phth CP/H2O2 system showed 5-cycles reuse for MO degradation decreasing from 89.7% to 73.5%. In some detail, proposed mechanisms for H2O2 decomposition and MO degradation and the inter-relation between them are introduced to account for the best degradation at initial pH 7.