Secondly, POM-based organic-inorganic hybrid materials are obtained by organic modification of POMs. On the one hand, organic ligands can improve the light absorption properties of POMs so that they can be activated in the visible region. On the other hand, metal organics can modulate the band gap of POMbased materials to improve photocatalytic performance. In 2016, Zhang et ). Thirdly, loading POMs on appropriate carriers such as MOFs and TiO2 can overcome the problem that POMs are highly soluble in water. In 2021, Jiao et al. prepared two cases of POM@MOFs, Ni3PW10@NU-1000 and Ni3P2W16@NU-1000. They were used as a photocatalyst to drive the hydrogen evolution reaction. Under the minimum optimization conditions, their hydrogen evolution rates were 3482 μmol g -1 h -1 and 13051 μmol g -1 h -1 , respectively. The authors think that the high catalytic performance of Ni3P2W16@NU-1000 is attributed to two points. On the one hand, Ni3P2W16 can store more electrons than Ni3PW10, and reversible multi-electron and proton storage capacity can significantly improve its photocatalytic activity. On the other hand, the molecular size of Ni3P2W16 matches the mesoporous and microporous sizes of NU-1000. Ni3PW10 is easily removed from the NU-1000 support during the catalytic process due to its small size (Figure ). Figure shows terminology clusters by average year of occurrence, where the colour change from white to red represents the dependence of popular terms on time. The most recent popular terms appear in cluster #2, which means that current scholars focus on the Application and performance of POM-based photocatalysts. Table shows a relatively high frequency of current ten terminologies, which intuitively show "carbon dioxide reduction", "energy conversion and storage", and "mixedaddendum polyoxometalate" are popular terminologies and are most likely to be research hotspots in the coming years. Reproduced with permission. Copyright 2016, Elsevier. (c) Structure of Ni3P2W16@NU-1000. Reproduced with permission. Copyright 2021, Elsevier.