Sulfur-functionalized metal-organic frameworks: Synthesis and applications as advanced adsorbents

Metal-organic frameworks (MOFs) are a class of crystalline inorganic-organic hybrid porous materials. Sulfur-functionalized MOFs (S-MOFs) are a subclass of MOFs that show some distinctive advantages and extensively studied in solid-phase extraction. In this review, we present a summary on the synthesis and adsorptive application of S-MOFs, and highlight the benefits of sulfur-functionalization. Three most widely used synthesis strategies, namely direct synthesis, post-synthetic modification and composite materials are developed to prepare S-MOFs. Based on hard-soft-acid-base (HSAB) theory, S-MOFs find practical applications in the adsorption of heavy metal ions, especially for mercury. Besides, efficient adsorption of inorganic non-metallic compounds and organic molecules is also reported. Finally, challenges and further perspectives of S-MOFs are presented and discussed in detail to achieve better advancement.