## 1 Introduction
It is noteworthy that during the metal-organic frameworks synthesis process, the framework's pores can capture solvent molecules, further highlighting the complexity and required reliability in producing such materials [18; 19]. Pure crystalline materials characterized by high porosity and surface area play a fundamental role in influencing both the chemical and physical attributes and are crucial in various applications such as catalysis and gas sorption and energy storage application. Surface textural properties have a significant impact on the surface area. Furthermore, the pore size distribution also plays a key role in shaping the extent of hydrogen adsorption within these materials [20; 21]. Moreover, it was observed that under high-pressure conditions, there exists a direct relationship between the capacity for CO\({}_{2}\) adsorption and the BET surface area and the pore volume [22]. Differences in the synthesis methods of MOFs result in variations in phase purity, crystal defects, and the presence of unreacted guest molecules within the pores of the as-synthesized MOFs. These variations are directly related to changes in the surface area [15]. [PERSON] et al. [23] employed a MOF water reconstruction method to enhance the crystallinity and BET surface area of defective MIL-100(Fe) synthesized through a chemomechanical method. In another approach, [PERSON] et al. [10] used double purification to clean MIL-100(Fe) synthesized hydrothermally. The process involved hot water to dissolve ionic species and organic molecules and hot ethanol for the non-reacted acid linker. The purified sample showed a notably increased surface area compared with unwashed samples. The development of environmentally sustainable synthesis procedures employing, e.g., sustainable compounds or low energy consumption and coupled with efficient filtering and purification techniques represents a highly promising way for obtaining highly crystalline MOFs. This very stimulating challenge holds great potential for the assessment of high-performance adsorbent materials with suitable sustainability features such as gas capture and energy storage applications [24,25]. In light of this, the aim of this research study is, by following the green chemistry principles, to assess a green hydrothermal synthesis, without using HF acid or other toxic reagents to obtain a high-purity MIL-100(Fe) MOF. The use of HF in the synthesis of MIL-100(Fe) has several drawbacks. First, HF is a highly hazardous chemical that can cause severe burns and respiratory problems. Its toxicity and corrosive nature necessitate stringent safety measures, which can increase the complexity and cost of the synthesis process [26]. Furthermore, HF could contribute to impurities that may adversely affect performance, thus influencing the washing procedure and also limiting the scalability of MIL-100(Fe) production, as it requires specialized equipment and handling procedures [26,27]. To address these challenges, the present study focuses on exploring the impact of HF-free hydrothermal synthesis modifications on the purity, adsorption performance, and potential applications of MIL-100(Fe). In particular, we investigate the effect of synthesis conditions and washing protocols on the properties and crystallinity of MIL-100(Fe). In addition, the adsorption capacities of MIL-100 (Fe) for various gases, such as hydrogen, carbon dioxide, and water vapor, were examined in order to investigate the absorption-desorption capacities of said material in different environmental conditions. The magnetic properties of the MOF materials were not investigated in our study, as our focus was specifically on their sorption capacity, particularly toward water vapor and other gases relevant to our application. By analyzing the adsorption process, this study aims to better understand the potential applicability of this material for thermal energy or specific gas storage.