Removal of H2S from Sour Gas Using MOF-303: Pressure-Dependent Crossover from Desulfurization to Dehydration with Comparison to MOF-333 and MOF-LA2–1

Abstract Sour gas treatment remains a major obstacle in the natural gas industry. Metal–organic frameworks (MOFs) offer a potential route to efficient sweetening; however, real natural-gas streams are multicomponent and typically contain water vapor, which suppresses H2S selectivity by competing for adsorption sites. Motivated by its established use in atmospheric water harvesting, we evaluate MOF-303 and compare it with two additional high-water-uptake frameworks, MOF-333 and MOF-LA2–1, as candidate sorbents for sour-gas upgrading under realistic humid conditions. We combine grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) to quantify pure, binary, and ternary adsorption of H2S/CH4/H2O at 303 K. The pure H2S isotherm in MOF-303 rises steeply and saturates to ∼12.2 mmol g–1, and this strong affinity carries into CH4/H2S (dry) mixtures, yielding tens-level selectivities across pressures and compositions. When we introduce 5 mol % H2O (wet), we observe a pressure-dependent crossover: MOF–303 remains H2S-selective at sub-bar pressures up to about 0.5 bar and becomes highly selective for H2O above ∼1 bar, while CH4 remains consistently disfavored. We probe the molecular origin of this crossover by analyzing guest–framework interactions and competitive bindings in the pore. Comparative ternary simulations show that MOF-333 exhibits a similar but narrower H2S-selective window centered near 0.25 bar before crossing over to H2O-dominated adsorption, whereas MOF-LA2–1 remains strongly H2O-selective from 0.05 to 2 bar. Together, these results show that the pressure-dependent crossover is not a universal consequence of water affinity alone but instead arises from framework-specific binding-site chemistry and competitive pore filling, with MOF-303 providing the widest and most robust dual-function desulfurization-to-dehydration window among the materials examined.