Fabrication of Cu(BDC)0.5(BDC-NH2)0.5 metal-organic framework for superior H2S removal at room temperature

A mixed ligand Cu-based MOF, Cu(BDC)0.5(BDC-NH2)0.5 was synthesized by a rapid ultrasonication method for the adsorptive removal of hydrogen sulfide (H2S) gas at room temperature. The MOF has a sheet-like morphology with 100 nm thickness crystallized in the monoclinic symmetry (a = 11.27 Å, b = 14.82 Å, c = 7.95 Å, β = 110.8°) with C2/m space group. The surface area and pore volume was 19.4 m2 g−1 and 0.024 cm3 g−1, respectively. The XPS analysis confirmed a near equal proportion of Cu(I) and Cu(II)-sites in the MOF. The MOF showed the H2S adsorption capacity of 128.4 mg g−1 for 500 ppm of H2S flowing at a rate of 100 mL min−1, which is among the highest values reported for Cu-based MOFs. The spent MOF was regenerated by a methanol and UV-irradiation method, which significantly improved the adsorption capacity. The H2S adsorbed onto the MOF by breaking Cu-carboxylate bonds with the formation of covellite CuS nanoparticles and sulfates. The spectroscopic analysis predicted a Cu(OH)-type sites after UV-irradiation along with increased surface area, which were responsible for an enhanced adsorption capacity of the regenerated sample.