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= MOF-545 = MOF-545 is a Metal Organic Framework with the molecular formula Zr6O8(H2O)8(C48N4O8H26)2.This framework has a face-centered-cubic (fcu) and csq topology with high thermal and chemical stability. MOF-545 was first discovered and characterized in 2012 along with MOF-525. Potential applications include gas separation and storage, catalysis, conductivity, and light harvesting.

Structure & Properties
Metal-organic frameworks (MOFs) are a new class of crystalline porous materials with fascinating structures and intriguing properties, such as permanent porosity, high surface area, and uniform open cavities.

MOF-545 has the largest pores of any zirconium-based MOF, with a pore diameter of 36 Å. The larger pores (mesopores) in MOF-545 allow for greater diffusion and transport of molecules across the framework, thereby resulting in a higher efficiency of catalysis as opposed to MOFs with smaller pores. The metal is connected to four 8-connected Zr6 clusters which generates a csq topology (shown in Figure 3). In contrast, a similar Metal Organic Framework, MOF-525, exhibits a ftw topolgy (also shown in Figure 3). MOF-545-Fe, a metallated version of the framework (shown in Figure 1), crystallizes in the hexagonal space group with unit cell parameters a = 42.545 Å and c = 16.96 Å. In addition to iron, MOF-545 can also be metallated with copper or manganese. Studies have observed catalytic rate enhancement due to the larger surface areas and faster diffusion through MOF crystallites. Furthermore, the ability of MOFs to maintain structural stability in high temperatures and acidic environments makes them desirable as catalysts.

Synthesis
0.0185 mmol of MOF-545 can be synthesized by first adding 37.5 mg (0.111 mmol) of zirconyl chloride octahydrate to 10 mL of DMF and sonicating the solution for 30 minutes. Then, 6.5 mg (0.037 mmol) of tetrakis(4-carboxyphenyl)porphyrin is added to the solution. After ten more minutes of sonication, 7 mL of formic acid is added to the solution. The solution is then placed in two 20 mL scintillation vials and heated at 130 °C for three days. The single crystals are typically collected by filtration and washed with 5 × 10 mL of DMF over a three-hour period. The DMF can then be replaced by 5 × 30 mL of acetone over a five-day period which can be removed by heating the solution to 120 °C under vacuum (30 mTorr) for 48 hrs.

Analysis
The crystal structure of MOF-545 was characterized solely by Power X-Ray Diffraction (PXRD) data. Most Metal Organic Frameworks have unique PXRD spectra which can be used to quickly confirm their identity.

Applications
Many applications for MOF-545, including gas separation and storage, catalysis, conductivity, and light harvesting are currently being researched, but have not yet been commercialized. In order to provide an active site inside the framework, the poryphrin sites within the molecules must be metallated, allowing for catalytic activity and the selective adsorption of gases.

The incorporation of active metal sites into MOF materials has been shown to enhance their gas adsorption and catalytic properties. For the incorporation of a porphyrin binding unit into MOF-525 and MOF-545, H4-TCPP-H2, the porphyrin units are known for enabling metal complexation into MOFs. Although many MOFs that contain porphyrin units have been synthesized, few have both accessible porphyrin binding sites and permanent porosity. Metallated porphyrins are known to be catalytically active and adsorb gases selectively. In addition, heterogeneous catalysts like MOF-545 allow for easier post-reaction separation and recyclability than homogeneous catalysts.

Previous research has shown that MOF-545 can be utilized as a catalyst in the photooxidation of a mustard-gas simulant, Chloroethyl Ethyl Sulfide (CEES). Though hydrogen peroxide has also proved successful as a catalyst and oxidizing agent, MOF-545 was proven to be more convenient and effective in the detoxification of mustard-gas. Whereas H2O2 produces a toxic byproduct due to its strong oxidizing nature, MOF-545 was used as a photosensitizer to generate O2, which then selectively oxidized the CEES, without producing the toxic sulfone. This experiment shows how MOFs may be utilized for air-filtration devices and effective detoxification of chemical warfare agents.