Hydrogen sulfide (H2S) is a hazardous gas known for its toxicity, unpleasant odor, lack of color, flammability, and acidic properties, posing substantial health and safety risks and the potential for corroding metal structures [1,2]. H2S emissions are prevalent in various industrial processes, including mining, paper production, oil and gas refining, wastewater treatment, waste disposal sites, and agriculture. The gas is of particular concern due to its conversion to sulfur dioxide, contributing to the formation of acid rain. Additionally, given its higher density than air, H2S tends to accumulate in inadequately ventilated, low-lying areas [[3], [4], [5], [6]].

Beyond its health implications, H2S can cause equipment corrosion and damage, necessitating its removal from industrial environments. Commercially, several methods are developed to eliminate H2S from gas streams, such as alkaline/amine scrubbing, chemical oxidation, biofiltration, catalytic oxidation, and surface adsorption within porous media. Porous metal oxides, activated carbons, and zeolites are frequently used as adsorbents due to their extensive specific surface area, porous structure, thermal resistance, and selectivity [[7], [8], [9]]. While certain metal oxides, such as molybdenum and tungsten oxides, exhibit robust desulfurization capabilities, they encounter temperature constraints due to carbide formation. Mixed metal oxides also tend to have lower adsorption capacities compared to zeolite-based adsorbents [10]. Activated carbons exhibit high H2S adsorption capacities but suffer from inadequate mechanical stability, leading to increased tortuosity and fines formation due to numerous micropores [11].

Zeolites, serving as highly porous molecular sieves for a wide array of chemical species, demonstrate exceptional H2S adsorption capacities, with regeneration being more practical and cost-effective [12,13]. The zeolite realm encompasses over 200 discovered or synthesized variations, with numerous hypothetical zeolite frameworks under consideration. Hence, the challenge lies in identifying the optimal zeolite for efficient H2S removal. Numerous studies have been aimed to elucidate the adsorption mechanism of H2S in various zeolite types, including zeolite A (LTA), zeolite Y (FAU), zeolite X (FAU), ZSM-5 (MFI), and natural zeolites (mordenite, clinoptilolite, erionite, phillipsite, ferrierite). The mechanism is found to be contingent on various factors including pore size, Si/Al ratios, cation species, and active component loading. Nevertheless, consensus remains elusive, as some studies propose elemental sulfur formation as the primary mechanism, while others suggest acid-base reactions [[14], [15], [16]].

In most instances, industrial gases consist of a combination of acidic (such as H2S and CO2) and polar species (like CO and H2O), which can compete with, and at times, displace H2S during adsorption [17]. Kumar et al. conducted an extensive investigation into the influence of these coexisting compounds on H2S adsorption, utilizing Na, Ag, and Cu-exchanged FAU zeolites at both high and low Si/Al ratios. The authors concluded that NaX zeolite exhibited minimal capability to capture H2S in the presence of CO, CO2, or H2O. CuX and CuY zeolites showed reduced H2S selectivity in the presence of CO. However, AgX and AgY zeolites demonstrated significant H2S adsorption capacities, approximately 30–40 mg/g, even when the H2S concentration in the mixture was 10 ppm, with all three components present [18]. A noteworthy exploration into polarity-based adsorption on zeolites was conducted by Mohammed and Nassrullah [19]. They synthesized zeolite 5 A using kaolin clay and investigated the removal of H2S from liquefied petroleum gases (LPG) in the presence of H2O. Interestingly, their findings revealed that H2O exhibits stronger adsorption compared to H2S. This study emphasizes the significant impact of even trace amounts of water on reducing the adsorption capacity of other gases on zeolites and decreasing their intracrystalline diffusivity [20].

Among the high-performing zeolites for removal of acidic species from natural gas, zeolite [Al4Si4O16] [Li4(H2O)4], commonly referred to Li-ABW, stands out as one of the top candidates. Liu et al. found that this zeolite is as a promising adsorbent with strong potential for commercial applications in multi-purpose gas separation, including the removal of acid gases from natural gas and carbon capture in power plants [21]. This particular zeolite contains water molecules that can be expelled through heating, resulting in empty voids within the crystal lattice, rendering it suitable for molecular filtration purposes [22,23]. Given the similarities in polarity and molecular size between H2O and H2S, it is a reasonable proposition to investigate the potential of Li-ABW zeolite for H2S adsorption. Moreover, it is noteworthy that the performance of Li-ABW zeolite in adsorbing H2S molecules in the presence of water molecules has not been comprehensively evaluated, adding to the novelty of this study.

Density functional theory (DFT) is as valuable tools in materials science for predicting material behavior, either predicting unknown properties, or validating and refining experimental findings. These techniques offer cost savings, enhanced safety, and the ability to address challenging experiments [24]. Chen et al. utilized DFT for the theoretical investigation of the structure and acidity of zeolite HSAPO-34 [25,26]. Gorai and colleagues conducted DFT calculations to explore the impact of various chemical species on the physical properties of a porous structure of carbon nitride [27,28]. In this study, we utilize DFT calculations to explore the adsorption behavior of H2S molecules in the Li-ABW zeolite, examining both its interaction in the presence and absence of water molecules. The subsequent section details our methodology, followed by the presentation of results encompassing adsorption structures, energies, Bader charge analysis, and electronic properties of the systems under study. Conclusions drawn from our findings are provided in the final section.