Theoretical investigation of hydrogen sulfide capture from methane binary mixture using s-heptazine-based metal–organic framework

Context: MOFs are promising candidates for the capture of H₂S and CO₂ from raw biogas. The presence of H₂S residues in natural gas pipelines can cause corrosive damage and reduce energy efficiency. H₂S capture from biogas presents several challenges due to its high toxicity and its corrosiveness. Microporous MOFs incorporating Lewis basic sites have demonstrated efficient capture of small and polar gas molecules such as CO₂ and H₂S from gas binary mixtures. In the quest to design and investigate functional materials to support the energy transition, specifically for the purification of RNG gas, we theoretically investigated the potential of s-heptazine-based IRH-1 for H₂S capture from CH₄ mixtures. IRH-1 exhibited significantly higher adsorption capacities for H₂S (2.60 mmol/g) and CO₂ (2.68 mmol/g) compared to CH₄ (0.98 mmol/g) at 100 kPa and 298 K simulated by GCMC. All computed average energies for H₂S were below 20 kJ/mol, indicating an exothermic physisorption behavior within the pores of IRH-1. IAST revealed remarkable H₂S selectivity of IRH-1 for CH₄/H₂S binary mixtures at 5%, 10%, 15%, and 20% of H₂S at 100 kPa. Methods: GCMC simulations were performed with the BIOVIA Materials Studio 5.0 package using LJ potentials and UFF parameters to investigate the adsorption of pure H₂S gas in the IRH-1 material. The IAST method was used to predict the adsorption behavior of H₂S in different H₂S/CH₄ gas mixtures. The IAST calculations were performed using the Python package pyIAST, which allows the prediction of adsorption isotherms for mixed gases based on the adsorption isotherms for pure gases by numerical integration of the Gibbs adsorption approach. Graphical abstract: (Figure presented.).