Covalently crosslinked zirconium-based metal-organic framework aerogel monolith with ultralow-density and highly...

Composites of MOFs and aerogels (MOFACs), as a new class of nanostructured materials, attract increasing attention due to their favorable adsorption properties. Herein, UiO-66-NH₂-CS aerogel monolith (UNCAM) was synthesized by covalent crosslinking with hierarchical structure, exhibiting effective and stable adsorption of Pb(II) ions. The aerogel monolith containing 50% MOF particles possesses a ultra-low density of 15.8 mg·cm^-3, which is mainly attributed to the highly porous structure. Meantime, UNCAM can be described more suitable by the pseudo-second-order model and shows a higher mass transfer rate. The highest Pb(II) adsorption capacity of aerogel monolith is up to 102.03 mg·g^-1 (1.612 × 10⁶ mg·m^-3), which is comparable to literature reports. The adsorption of Pb(II) by UNCAM is an endothermic and spontaneous process and consistent with the Langmuir model, indicating that the adsorption process belongs to monolayer adsorption and chemisorption. Furthermore, the adsorption mechanisms of coordination interaction between N and Pb (II) were confirmed, and the O also played a synergistic role in adsorption on a certain degree. Lastly, The UNCAM retained 90.12% adsorption ability after three cycles. This strategy may provide an effective and versatile pathway to convert the bulk MOF particles into a shapeable form and sequentially branch out their applications in pollutant treatment fields.