Enhanced natural gas purification using Cyclodextrin-Based Metal-Organic frameworks with polar Nanotraps

The separation of methane (CH4) from higher alkanes such as ethane (C2H6) and propane (C3H8) is a critical process in natural gas purification, which is essential for both enhancing the calorific value of natural gas and obtaining valuable feedstocks for chemical synthesis. Traditional methods struggle with the trade-off between adsorption capacity and selectivity due to the physical similarities of these alkanes. In this study, we introduce two cyclodextrin-based metal-organic frameworks (gamma-CDMOF-1 and gamma-CDMOF-2), which feature expansive polar cavities that significantly improve selectivity and adsorption capacity. These frameworks utilize uncoordinated oxygen sites within their structure to facilitate C-H center dot center dot center dot O hydrogen bonding interactions, thereby selectively capturing C3H8 and C2H6 over CH4. Computational simulations, including Grand canonical Monte Carlo (GCMC) and density functional theory (DFT) analyses, affirm the frameworks' ability to selectively recognize and bind target molecules. Empirical breakthrough experiments demonstrate that gamma-CDMOF-1 can achieve CH4 purities exceeding 99.99 %, thereby indicating its potential for practical applications in natural gas purification. The findings suggest that integrating multiple polar sites within MOF cavities offers a promising strategy for developing advanced materials for the energy sector.