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Previously the non-cubic β-pyrochlore polycrystalline compounds Rb 0.95 Nb x Mo 2-x O 6.475-0.5x (x = 1.31-1.663) have been obtained in the ternary system Rb 2 O-Nb 2 O 5 -2MoO 3 . However, using special synthesis condition leads to the formation of cubic Fd-3m β-pyrochlore Rb 0.9 Nb 1.625 Mo 0.375 O 5.62 with small size particles and surface area of 15 m 2 /g. The Rb 0.9 Nb 1.625 Mo 0.375 O 5.62 powder has been investigated by X-ray powder diffraction analysis and scanning electron microscopy with X-ray microanalysis. The crystal structure refinement has been performed using the Rietveld method. The electronic structure and optical band gap of Rb 0.9 Nb 1.625 Mo 0.375 O 5.62 have been studied in comparison to similar non-cubic composition Rb 0.95 Nb 1.625 Mo 0.375 O 5.66 . The photocatalytic properties of Rb 0.9 Nb 1.625 Mo 0.375 O 5.62 have been investigated on the example for dyes solution oxidation under UV irradiation. The dependence on the photocatalytic properties of dye type and catalyst mass has been studied. It has been observed that the main oxidative species for dye oxidation is hydroxyl radicals. The phase and composition stability of catalyst powder have been confirmed.

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Heterogeneous photocatalysis has been considered one of the most attractive alternative routes to transforming naturally abundant, clean, and sustainable solar energy into chemical energy. Nowadays, the most popular heterogeneous photocatalyst, titanium dioxide, has already found applications for water splitting to produce hydrogen and oxygen, for the degradation of organic pollutants, for air purification, and for the creation of self‐cleaning coatings. However, TiO2 has a significant limitation: a large band gap (3.0–3.4 eV) that makes it impossible to use anything other than ultraviolet illumination to initiate photocatalytic processes. With a focus on efficient solar‐energy utilization, the development of new photocatalysts that are sensitive to visible light is an important direction in the theory and practice of heterogeneous photocatalysis. In this regard, the use of metal–organic frameworks (MOFs) is an attractive route; they have emerged as an interesting class of materials for applications in photoreactions due to their flexible tunability in composition, structure, and functional properties, along with their facilitated adsorption towards chemicals and their efficient light absorption. Moreover, they can be composed with other semiconductors to produce heterojunctions (e.g., type‐II, Z‐scheme, and S‐scheme), whose effectiveness in photogenerated charge separation has already been proven by many examples. The present critical review reports progress over the last 5 years in the preparation and activity of metal–organic framework‐based heterojunction photocatalysts for the degradation of organic pollutants. © 2022 Society of Chemical Industry (SCI).

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