The noble gas Helium (He) is the smallest gas (kinetic diameter d kin (He) = 2.60 Å) and is a rare resource, making efficient production important. He is holding significant value for the future of the energy sector and for advancement of different high tech sectors, such as medicine and research. Natural gas (methane, CH 4 , d kin = 3.8 Å) as one of the primary fossil energy source can contain up to 4 % He, but usually lower concentrations are observed. The massive fossil fuel exploitation over the past century resulted in highly elevated levels of He in the atmosphere, while there is an ever craving need in the technology sector for He, for example in medical applications, such as MRI (magnet resonance imaging), or technological application in lasers, spectroscopy and deep cooling. Crude He sources are uncommon and have largely ceased exploitation due to their importance for the future of technology. He is a non-renewable resource, thus generating strong interest in its separation from Herich natural gas. While the components of He-rich natural gas can be separated through cryogenic distillation, an energy efficient process can be developed from diffusion driven molecular sieving membrane technology. Highly promising molecular sieving materials are Metal-Organic Frameworks (MOFs), hybrid materials consisting of inorganic metal-centres or clusters and organic linker molecules, which are connected via coordination bonds showcasing an extensive array of crystalline structures with a broad spreading from non-porous to highly porous networks. He is usually referred to as a non-adsorptive gas because it requires highly elevated pressure or very low temperatures to show condensation in pore systems, which is why diffusive separation is highly favoured instead. However, discussions have persisted regarding the molecular sieving capabilities of MOFs over recent years. This debate stems from the characteristics of the building blocks -the inorganic metal centre or cluster and the organic linkeras well as the nature of their coordination bonds. While the building blocks offer numerous interesting features, they often render the frameworks unreliable for precise molecular sieving. This unreliability is primarily attributed to the flexibility of the organic components and the linkers, which can undergo rotational conformation changes and show thermal lattice vibrations, along with energetic host-guest interactions contributing to the so-called "breathing" effect . MOF-based membranes have been developed and were tested for He-upgrading, but they significantly suffer from the large pore sizes, grain boundaries causing insufficient molecular sieving capabilities.