Highly Hydrophobic Isoreticular Porous Metal–Organic Frameworks for the Capture of Harmful Volatile Organic Compounds

• DOI: 10.1002/ange.201303484
• Publication Date: 2013-06-26T13:49:54Z
• Authors: Natalia M. Padial; Elsa Quartapelle ...; Carmen Montoro; Elena López; J. Enrique Oltra; Valentina Colombo; Angelo Maspero; Norberto Masciocchi; Simona Galli; Irena Senkovska; Stefan Kaskel; Elisa Barea; Jorge A. R. Navarro
• Keywords: air filters ; chemical warfare agents ; gas chromatography ; metal-organic frameworks ; X-ray diffraction; 13. Climate action; air filters; chemical warfare agents; gas chromatography; metal-organic frameworks; X-ray diffraction; 11. Sustainability; 02 engineering and technology; 0210 nano-technology; 6. Clean water; 12. Responsible consumption

The release of toxic pollutants into the environment, which includes oil spills, leaks of harmful industrial products, and the deliberate emission of chemical warfare agents is a risk of growing concern. Worthy of note, oil spill cleanups amount to over 10 billion dollars annually. Remediation of these environmental problems involves the use of large amounts of adsorbents such as sand, activated carbons, or zeolites. However, the effectiveness of such adsorbents is often limited by their affinity to moisture. Consequently, the search for highly hydrophobic porous materials to be used as suitable stopgap of harmful organics spills has become of paramount importance. In the past years, porous metal–organic frameworks (MOFs) have been extensively studied to explore their possible applications in near future technologies for the safe storage of energetically and environmentally relevant gases. The tunable nature of their pores might be beneficial also in cushioning environmental problems caused by the release of harmful volatile organic compounds (VOCs). A remarkable example of the design amenability of MOFs is the well-known isoreticular [Zn4OL3] series (L= arene-dicarboxylate), wherein the size and the functionality of the pores can be modulated in a highly rational and systematic way. Nevertheless, the advantageous structural features of this family of MOFs are readily hampered by its high sensitivity to moisture, which limits its practical applications. A similar size-scaling approach has been applied by Lillerud and coworkers on the isoreticular [Zr6O4(OH)4L6] series, [9] evidencing that a significant improvement in the stability of the material can be achieved with an appropriate combination of dicarboxylate linkers and oxophylic metal fragments. Alternately, it is possible to take advantage of the enhanced stability imparted by polyazolate-containing ligands in combination with borderline metal ions. Accordingly, we designed and isolated an isoreticular series of porous MOFs, the pore size and polarity of which was modulated by coupling stiff bi-pyrazolate or mixed pyrazolate/carboxylate linkers (Scheme 1) to Ni hydroxo clusters acting as 12-connected