(293g) Growth of 2-D Porphyrin-Based Metal–Organic Frameworks on Nonwoven Textiles As Effective Adsorbents for Toxic Industrial Chemicals and Chemical Warfare Agent Simulants

Micro- or mesoporous metal-organic frameworks (MOFs) have been well-known for possessing exceptionally high surface area with readily modifiable pore structures. Among a wide range of applications, MOFs are known for adsorbing and reacting with chemicals (e.g., chemical warfare agents (CWAs) and toxic industrial chemicals (TICs)) and this characteristic has been deemed the area of research with highest priority. Although some of the MOFs which have proved to exhibit substantial potential as adsorbents for toxic chemicals, they have not been effectively used as adsorbents under humid conditions (e.g., 80% RH) due to their poor stability against water as well as toxic challenge gases. Considering such shortcomings of the MOFs (e.g., HKUST-1), we had sought out a chemically analogous MOF with accessible metal sites that maintains its chemical integrity upon exposure to water and toxic chemicals.

Here, we mainly focus on highly robust 2D Cu-TCPP MOFs, composed of a copper paddle-wheel structure of metal clusters connected by porphyrin-based organic linkers, as well as successful control of the orientation of 2D MOF structures on polymeric fibrous scaffolds to implement them most effectively. As for the synthesis of 2D MOF/Fabric composite materials, we took advantage of the atomic layer deposition (ALD) technique to prepare ZnO coated polypropylene (PP) (i.e., PP@ZnO) fiber substrates, followed by a wet chemical process converting the ZnO film on PP to intermediate hydroxy double salt (HDS(Zn,Cu)) layered structures at room temperature. These layered HDS structures were used as templates to guide a vertical orientation of the Cu-TCPP while reacting with porphyrin linker solution at 40 ^oC for 12 h. We proved that our suggested MOF growth method is markedly promising in the quality and adherence of Cu-TCPP onto fiber substrates with high BET surface area (~200 m²/g_(MOF+Fiber)). This is quite phenomenal compared to composite materials (< 10 m²/g_(MOF+Fiber)) made via a conventional solvothermal approach in the absence of HDS intermediates under the same synthetic condition.

Most importantly, the 2D MOF/Fabric materials were tested for the removal of ammonia and 2-CEES, a sulfur mustard simulant, by conducting micro-breakthrough tests under dry and humid conditions. Dynamic loading (mol_(adsorbate)/kg_(adsorbent)) of NH₃ on the composite materials shows at maximum value 12× higher in dry conditions and 20× higher in humid conditions than that of control PP fibrous mats. As for the dynamic loading (mol_(adsorbate)/kg_(adsorbent)) of 2-CEES gas to the composite materials, it exhibits a maximum value 21× higher in dry conditions and 17× higher in humid conditions than that of control PP fibrous mats.

We will also discuss the mechanism of 2D Cu-TCPP MOF growth onto the fibrous substrates and deal with stability of the composite materials under water and after exposure to the toxic chemicals tested. Furthermore, the universality of the synthetic approach will be addressed.