Degradation of micropollutants by metal organic framework composite-based catalysts: A review

The presence of various micropollutants in different water sources has become a major problem due to their significant impact on both humans and the environment. This review highlights the different types of micropollutants present at the global scale and the methods applied to reduce and possibly eliminate them. These methods include membranes, adsorption and photocatalysis. While membrane filtration is extremely effective, one membrane can eliminate only a few micropollutants and its deployment remains expensive. On the other hand, adsorption constitutes a very efficient and cost-effective method, but the production of adsorbents is extremely energy intensive. Lastly, the photocatalysis method is considered to be the most promising as it avoids the problems associated with the aforementioned methods. Specifically, photocatalysts make use of direct sunlight in order to degrade micropollutants. Several types of photocatalysts, including biochar, Mxenes, nanoscaled zero valent iron, and MOFs, are discussed. Unlike the first four aforementioned types, MOFs can be combined with different materials to enhance the overall property of the composite and its efficiency in the degradation of micropollutants. The MOF-catalysts discussed in this paper include biomimetic MOFs, enzyme MOFs, and Fenton-like MOFs. The obtained system is referred to as MOF-composite-based catalysts. MOFs can be synthesized by combining an appropriate organic linker with a metallic cluster that would provide the material with the required properties for photodegradation. Several metal-organic framework catalyst composites synthesis approaches are reviewed and discussed. The selection of the approach depends on the requirements associated with the application of interest. To date, extensive research has been conducted on the performance analysis of metal-organic framework composites to investigate their efficiency in the removal of micropollutants. Several studies demonstrated their great removal capability which may reach up to 99 %. Finally, cost, health and environmental considerations are discussed with the view of the industrial applicability of MOF-composite-based catalysts. This comprehensive review presents the current state of the art and proposed promising research directions for the implementation and advancement of MOF-composite-based catalysts for micropollutants degradation.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The presence of various micropollutants in water sources has become a major problem with significant impacts on humans and the environment. This review focuses on the types of micropollutants globally and the methods used to reduce and eliminate them, including membranes, adsorption, and photocatalysis. Among these methods, photocatalysis shows the most promising potential by utilizing direct sunlight to degrade micropollutants.