Two-Dimensional Metal-Organic Framework Nanostructures Based on 4,4′-Sulfonyldibenzoate for Photocatalytic Degradation of Organic Dyes

Four new two-dimensional metal-organic frameworks, namely, [Zn-2(sdba)(2)(pbisopix)](n) (KLU-8) (KLU is referring to Kirklareli University), {[Cd-2(sdba)(2)(pbisopix)]center dot 2H(2)O}(n) (KLU-9), [Cd(sdba)(pbisopix)](n) (KLU-10), and [Cd-(sdba)(pbetix)](n) (KLU-11) have been synthesized using a V-shaped 4,4'-sulfonyldicarboxylic acid (H(2)sdba) as anionic and 1,4-bis((2-isopropylimidazol-1-yl)methyl)benzene (pbisopix) or 1,4-bis((2-ethylimidazol-1-yl)methyl) benzene (pbetix) as neutral ligands and characterized by various techniques. In KLU-8 and KLU-9, the {M-2(CO2)(4)} secondary building units (SBUs) are connected by sdba(2-), while in KLU-10 and KLU-11 Cd(II) ions bridged by sdba(2-) form a 2D structure of MOFs revealed by single crystal X-ray diffraction analyses. The topology of MOFs is found to be a 2D sql network. The synthesized MOFs are stable in aqueous medium up to 7 days. KLU-10 and KLU-11 were well-exfoliated via facile sonication process in 10 min, at room temperature, whereas, KLU-8 and KLU-9 showed poor exfoliation yield because of their interpenetrated structure according to the FESEM images. Furthermore, the surface area measurement also proved the exfoliation of MOFs; that is, the exfoliated samples exhibited higher surface area than that of bulk counterparts. The photocatalytic properties of exfoliated MOF nanostructures in the photodegradation of three organic dyes (methyl orange (MO), methylene blue (MB), and rhodamine B (RhB)) have been investigated under UV/vis irradiation. The photodegradation efficiencies of MO, MB, and RhB can reach almost 100% within 40 min, 59% within 60 min, and 66% within 60 min, respectively in the presence of MOF nanostructures as photocatalyst and molecular oxygen as oxidant. The superior photocatalytic efficiency toward MO degradation of KLU-10 and KLU-11, might be attributed to the very high exfoliation yields of MOFs.