A critical review describes wastewater photocatalytic detoxification over Bi5O7I-based heterojunction photocatalysts: Characterizations, mechanism insight, and DFT calculations.

Bi 5 O 7 I-based photocatalysts have been extensively employed for wastewater photocatalysis thanks to their desirable catalytic properties. This review sums up the latest progress in Bi 5 O 7 I-based heterojunctions and provides crucial information about three main areas: synthesis approaches, characterizations, and their applications in wastewater photocatalysis. Special attention is given to the synthetic strategies, like co-precipitation, hydrothermal, solvothermal, sonication, and ionic liquid self-combustion, to obtain Bi 5 O 7 I-based heterojunctions with appropriate morphology, structure, physical, chemical, and optical characteristics. Deeply, it was detected that the structure of Bi 5 O 7 I inclines to build a 3D crystal structure by stacking the [Bi 5 O 7 ]⁺ slices with I⁻ ions. Beyond that, the Bi 5 O 7 I nanomaterials exhibited different morphologies, like nanoparticles, nanorods, nanosheets, and flower-like microspheres, manifesting excellent support structures to immobilize incorporated co-catalysts. Our review also highlights the major modification approaches, like doping, type II, p-n, Z-type, and S-type heterojunctions, that address the catalytic limitations of pristine Bi 5 O 7 I. Impressively, the density functional theory (DFT) calculations played a crucial role in simulating and characterizing the crystalline structure, band structure, work function, and charge transfer profile of these Bi 5 O 7 I-based heterojunctions. In more detail, doping with plasmonic nanoparticles could broaden the visible-light sensitivity of newly created Bi 5 O 7 I-based heterojunctions. Even though type II and p-n Bi 5 O 7 I-based heterojunctions allowed for excellent charge separation mechanisms, their redox potentials were insufficient to produce both ^•OH and ^•O 2 ⁻ radicals. On the other hand, Bi 5 O 7 I-based S-type and Z-type systems offered advantages for obstructing the charge reintegration rate, accelerating the photocarrier migration, expanding the photon absorption, and upgrading the redox potential. The applications of Bi 5 O 7 I-based heterojunctions in terms of the purification of pollutants are also reviewed, supported by a huge number of impactful experimental studies and DFT theoretical calculations. The Bi 5 O 7 I-based heterojunctions displayed superior catalytic performance against various environmental pollutants, like phenolic compounds, organic dyes, pharmaceuticals, microorganisms, Hg⁰, Cr(VI), and so on. The DFT calculations reflected an assistance role in proposing the degradation pathways of treated organic pollutants via Bi 5 O 7 I-based heterojunctions. Ultimately, this review may have a significant influence on the development of sustainable Bi 5 O 7 I-based photocatalysts with perfect photocatalytic properties. [Display omitted] • This review summarizes the latest progress in Bi 5 O 7 I-based heterojunction photocatalysts. • Special attention is given to the synthetic strategies of Bi 5 O 7 I-based composites. • The characterizations and the photoactivity of Bi 5 O 7 I-based catalysts have been explained in detail. • Modification strategies like doping, defects, and heterojunctions have been discussed. • The DFT calculations played a crucial role in justifying the catalytic behavior of Bi 5 O 7 I-based catalysts. [ABSTRACT FROM AUTHOR]