Revolutionizing environmental cleanup: the evolution of MOFs as catalysts for pollution remediation

Abstract

The global problem of ecological safety and public health necessitates, the development of new sustainable ideas for pollution remediation. In recent development, metal-organic frameworks (MOF) are the emerging technology with remarkable potential, which have been employed in environmental remediation. MOFs are networks that are created by the coordination of metals or polyanions with ligands and contain organic components that can be customized. The interesting features of MOFs are a large surface area, tuneable porosity, functional diversity, and high predictability of pollutant adsorption, catalysis, and degradation. It is a solid material that occupies a unique position in the war against environmental pollutants. One of the main benefits of MOFs is that they exhibit selective adsorption of a wide range of pollutants, including heavy metals, organics, greenhouse gases, water and soil. Only particles with the right combination of pore size and chemical composition will achieve this selectivity, derived from the high level of specificity. Besides, they possess high catalytic ability for the removal of pollutants by means of different methods such as photocatalysis, Fenton-like reactions, and oxidative degradation. By generating mobile active sites within the framework of MOFs, we can not only ensure high affinity for pollutants but also effective transformation of toxic chemicals into less harmful or even inert end products. However, the long-term stability of MOFs is becoming more important as eco-friendly parts are replaced with those that can be used repeatedly, and systems based on MOFs that can remove pollutants in more than one way are fabricated. MOFs can reduce waste production, energy consumption as compared to the other removal process. With its endless capacities, MOF technology brings a solution to the environmental cleansing problem, working as a flexible problem solver from one field to another. The investigation of MOF synthesis and principles will allow researchers to fully understand the potential of MOFs in environmental problem solving, making the world a better place for all of us.

Fig. 1. Properties and applications of metal organic frameworks. Reproduced with permission from ref. . Copyright (2022) The Royal Society of Chemistry.

Fig. 2. Representation of the synthetic scheme of metal organic frameworks. Reproduced with access provided by HEC.

Fig. 3. Synthetic and photocatalytic activity of synthesized Cd/Zr-MOF nanomaterials. Reproduced with access provided by Higher Education Commission (HEC).

Fig. 4. SEM images of M-MOF-5 (A and B), M-ZnO-500 analysis (C and D), and M-ZnO-550 (E and F). SEM image (G) and EDX elemental mapping (H–J) of M-ZnO-500. Reproduced with permission access provided by the University of Gujrat.

Fig. 5. Synthesis of NH₂-MIL-125/TiO₂/CdS yolk–shell and hollow H-TiO₂/CdS heterostructures. SEM (a–c) and TEM (d–f) images of NH₂-MIL-125 MOF, NH₂-MIL-125/TiO₂/CdS yolk–shell, and H-TiO₂/CdS. Reproduced with permission from ref. . Copyright (2018) American Chemical Society.

Fig. 6. Schematic of the microwave-assisted synthesis of NH₂-MIL-125(Ti) samples at different temperatures and periods, and SEM images of the samples: (A) 140 °C for 15 minutes; (B) 160 °C for 15 minutes; (C) 200 °C for 15 minutes; and (D) 200 °C for 4 hours. Reprinted with permission from ref. . Copyright (2021) Elsevier.

Fig. 7. Synthesis of metal organic frameworks through ball milling process. Reprinted with permission from ref. . Copyright (2020) MDPI.

Fig. 8. Synthesis of the pillared-layer MOF, {[Cu₂(Fu)₂(BPY)]·H₂O}n via a chemical process. Reproduced with permission from ref. Copyright (2022) RCS Advances.

Fig. 9. UiO-66-NH₂ synthesized via a novel sonochemical method. Adopted with permission from ref. Copyright (2023) Scientific Reports.

Fig. 10. Different techniques used for the characterization of metal organic frameworks.

Fig. 11. Left: XRD spectra of mixed-ligand [Co(BDC)(Phen)(H₂O)](1) and [Co(BDC)(DABCO)](2) MOFs. Top right (a–d): SEM-EDX analysis of mixed-ligand [Co(BDC)(Phen)(H₂O)](1) MOF. Bottom right (a–d): SEM-EDX analysis of mixed-ligand [Co(BDC)(DABCO)](2) MOF. Reprinted with permission from ref. . Copyright (2021) Springer.

Fig. 12. TEM pictures of MOF-5 synthesized using pulsed laser ablation (PLA) technique (250 nm scale). Reproduced with permission from ref. . Copyright (2021) Springer.

Fig. 13. Dynamic light scattering (DLS) results of R_A-MOF-74 and R_N-MOF-74. Adopted with permission from ref. . Copyright (2024) Springer.

Fig. 14. Thermogravimetric analysis (TGA) of four MOFs: NH₂-UiO-66(Zr), NH₂-MI(53), NH₂-Cd-BDC, and NH₂-MIL88(Fe). Reprinted with permission from ref. . Copyright (2022) Springer.

Fig. 15. Representation of MOF performance as a catalyst for the removal of various pollutants.

Fig. 16. Mechanistic representation of MOFs as photocatalysts for the degradation of heavy metals. Reproduced with permission ©copyright ref. .

Fig. 17. Degradation of Rhodamine B (RhB) dye using BiVO₄/MOF/GO nanocomposites. Reproduced with permission from ref. . Copyright (2020) Elsevier.

Fig. 18. Photocatalytic degradation of toluene by CQDs/UiO-66 MOG composites. Reprinted with permission from ref. . Copyright (2022) Elsevier.

Fig. 19. Photocatalytic degradation of pesticides using MOF@MPCA. Reproduced with permission from ref. . Copyright (2021) Elsevier.

Fig. 20. Adsorption and photodegradation of volatile organic compounds (VOCs) using MIL-100(Fe) under UV light. Reproduced with permission from ref. . Copyright (2022) Elsevier.

Fig. 21. In vitro antibacterial study of MIL-101(Fe)-T705. Reprinted with permission from ref. . Copyright (2022) MDPI.

Fig. 22. MOF-303 as an effective β-ray irradiation-resistant trap for capturing Th(iv) ions. Reprinted with permission from ref. . Copyright (2022) Elsevier.

Fig. 23. MOF-808-SO₃H as a photocatalyst for the removal of radioactive elements. Reproduced with permission from ref. . Copyright (2022) Elsevier.

Fig. 24. Ce-UiO-66-NH₂ MOF as a photocatalyst for the removal of phosphate ions from water. Adopted with permission from ref. . Copyright (2020) Elsevier.

Fig. 25. Oil–water separation using UIO-66-F4@rGO/MS as the nanocatalyst. Reproduced with permission from ref. . Copyright (2020) Elsevier.

Fig. 26. Properties of metal organic frameworks as photocatalysts.