Metal organic framework derived NaCo_xO_y for room temperature hydrogen sulfide removal

Novel NaCo_xO_y adsorbents were fabricated by air calcination of (Na,Co)-organic frameworks at 700 °C. The NaCo_xO_y crystallized as hexagonal microsheets of 100-200 nm thickness with the presence of some polyhedral nanocrystals. The surface area was in the range of 1.15-1.90 m² g^-1. X-ray photoelectron spectroscopy (XPS) analysis confirmed Co²⁺ and Co³⁺ sites in MOFs, which were preserved in NaCo_xO_y. The synthesized adsorbents were studied for room-temperature H₂S removal in both dry and moist conditions. NaCo_xO_y adsorbents were found ~ 80 times better than the MOF precursors. The maximum adsorption capacity of 168.2 mg g^-1 was recorded for a 500 ppm H₂S concentration flowing at a rate of 0.1 L min^-1. The adsorption capacity decreased in the moist condition due to the competitive nature of water molecules for the H₂S-binding sites. The PXRD analysis predicted Co₃S₄, CoSO₄, Co₃O₄, and Co(OH)₂ in the H₂S-exposed sample. The XPS analysis confirmed the formation of sulfide, sulfur, and sulfate as the products of H₂S oxidation at room temperature. The work reported here is the first study on the use of NaCo_xO_y type materials for H₂S remediation.