Mesoporous Co-MOF with semi-rigid V-shaped linker for toxic Cr (VI) ion reduction and degradation of rhodamine B dye under natural sunlight

Semi-rigid V-shaped bis(N,N-trimellitoyl)-4,4′-oxydianiline linker was designed to construct a novel mesoporous cobalt (II) metal organic framework (Co-MOF). Optical band gap of 3.23 eV was obtained using a Tauc formula, which confirms the semiconducting property of the synthesized Co-MOF. Further, the resulting Co-MOF, as photocatalyst, was investigated in environmental application for the reduction of toxic Cr (VI) to less toxic Cr (III) as well as in the degradation of organic rhodamine B (Rh B) dye in an aqueous medium under natural sunlight. As pH value is essential for the Cr (VI) reduction reaction, thus control experiment was conducted in the acidic pH range 2–6, where 90.76, 77.23 and 37.43% of reduction was observed at pH of 2, 4 and 6, respectively. Furthermore, the degradation of Rh B dye was also performed, where 98.89% degradation obtained within 90 min. The recyclability test was also assessed for Cr (VI) reduction reaction at pH 2 and for degradation of Rh B.