Cu(BDC)0.5(BDC-NH2)0.5: A superior metal-organic framework for room temperature H2S remediation

Cu(BDC)_0.5(BDC-NH₂)_0.5 was fabricated by sonicating an equal proportion of benzene-1,4-dicarboxylic acid (H₂BDC) and 2-aminobenzene-1,4-dicarboxylic acid (H₂BDC-NH₂) with a freshly prepared Cu(OH)₂ precipitate. The sheet-like MOF was 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 presence of Cu(I) and Cu(II)-sites in the MOF. The MOF had the highest H₂S adsorption capacity of 128.4 mg g⁻¹ at 298 K, which is among the highest values reported for Cu-based MOFs. The H₂S interacted with Cu-sites by breaking Cu−carboxylate bonds with the formation of covellite CuS nanoparticles and sulfates. The regeneration of spent MOF by a methanol and UV-irradiation method improved its adsorption capacity. The XPS analysis predicted a CuCO₃/Cu(OH)₂-type material after UV-irradiation, which was responsible for the reusability. It is one of the first studies with a novel adsorption-regeneration approach for H₂S removal using a mixed ligand Cu-based MOF.