| Abstract: Defect engineering is an effective strategy for modulating the structure of metal-organic frameworks (MOFs) to boost their performance in water treatment. The defect can be formed when the regular periodic arrangement of atoms or ions in the crystalline parent framework is broken due to the missing or dislocation of atoms or ions. In the field of defective MOFs, the types of defects are divided into (ⅰ) missing linker defects, (ⅱ) modified linker defects, (ⅲ) missing node defects, and (ⅳ) modified node defects. Although the construction of defective MOFs has received continuous attention, which remains challenging today. Up to now, there are two synthetic pathways to fabricate defective MOFs: the modulation during the synthesis process and the post-synthetic treatment methods. Specifically, defective MOFs can be fabricated by adjusting the synthesis conditions (temperature, the ratio of metal/ ligand, etc.), introducing modulators, thermal activation, metal node substitution, and so on. Many advanced techniques like X-ray diffraction (XRD), specific surface area analysis, thermogravimetric analyses-differential scanning calorimetry (TGA-DSC), electron paramagnetic resonance (EPR), X-ray photoelectron spectra (XPS), high-resolution transmission electron microscopy (HR-TEM), spherical aberration-corrected transmission electron microscope (AC-TEM), and X-ray absorption spectroscopy (XAS) can effectively affirm the defective structure of MOFs. In the field of water remediation, the construction of defective MOFs can boost their performance of advanced oxidation processes like photocatalysis, persulfate (PS) activation, and photo-Fenton by enhancing separation rates of photoinduced electron-hole, promoting the photoelectron transfer and narrowing the band gap compared with pristine MOFs. Moreover, because the defective sites are introduced in the framework, they act as dominant active sites in the PS system, promoting the generation of radicals and creating a nonradical degradation pathway. Meanwhile, defective MOFs with rich unsaturated coordination centers can provide more adsorption sites toward pollutants, further enhancing the adsorption capacities and rates of sorbents. This review summarized the fabrications, characterizations, and applications in the water treatment of defective MOFs. Meanwhile, the prospects of defective MOFs for pollutant removal from water are proposed in this review. |
