In 2018, Gregoire Paille et al. fixed [(PW9O34)2Co4(H2O)2] 10- in the pores of the Zr(IV) porphyrin MOF-545 hybrid framework. This is the first POM@MOF without any noble metal used for visible-light-driven oxygen evolution reaction (OER). Interestingly, both catalysts and photosensitizers are integrated with this POM@MOF. Porphyrin can enhance the oxidation ability as an organic ligand in MOF. At the same time, the suitability of POM size and MOFs pore size plays an important role in stabilizing the structure (Scheme 1 (d)). In 2020, Youven Benseghir et al. successfully co-immobilized [PW12O40] 3-and Cp*Rh(bpydc)Cl2 (bpydc= 2,2'-bipyridine-5,5'-dicarboxylic acid) catalysts in (PW12, Cp*Rh)@UiO-67. The compound showed good photocatalytic activity in converting CO2 to formic acid and hydrogen. Studies have shown [PW12O40] 3-and Cp*Rh(bpydc)Cl2 play an important role in the photocatalytic process. The catalytic activity of the POM-free Cp*Rh@UiO-67 is weak, and the Cp*Rh-free PW12@UiO-67 has no catalytic activity (Scheme 1 (e)). In 2018, -in the Cu-trz rings by Cu … O weak interaction. This is an efficient visible light photocatalyst with prominent photodegradation activity and HER activity (Scheme 1 (f)). Another high-frequency terminology in Cluster #1, "hydrothermal syntheses", represents a recent trend in POMbased materials synthesis methods. In synthesising POM-based materials, water or organic solvents such as methanol and acetonitrile limit the temperature of the reaction system. In addition, it is challenging to obtain inorganic-organic hybrid POMbased materials by the conventional solution method, which is attributed to the poor solubility of organic ligands at room temperature. Hydrothermal synthesis is usually carried out in closed containers, and the solubility of various precursors is enhanced due to the decrease in water viscosity. As shown in Figure , Yang's group used {Ni6PW9(H2O)5} as a secondary building block with a series of rigid carboxylic acid ligands to synthesise several new POM-based materials with 0D, 1D, 2D and 3D structures, implying that organic ligands as linkers are a practical and feasible synthetic strategy under hydrothermal conditions. In the past decade, various POM-based materials have been synthesised by the hydrothermal method. Figure . Designed syntheses of {Ni6PW9(H2O)5}-based POM-based materials.