Recent advances in selective separation of H2/CO2 gases by composites of MOFs

In this paper, metal-organic framework (MOF)-based composites are introduced as membranes for H2/CO2 separation. In industrial processes, the separation of hydrogen and carbon dioxide is a complex and vital procedure. Hydrogen (H2) can meet the world's growing energy needs as a high-energy-density, sustainable, and environmentally friendly resource. Industrial hydrogen production typically yields impure hydrogen streams containing small molecular contaminants, notably CO2. Compared to conventional technologies, adsorption-based processes for gas separation are of interest due to their simplicity, low cost, and high efficiency. Among different methods, the use of MOFs has become popular for gas separation due to adjustable pore sizes, high specific surface area, chemical versatility, and extremely high porosity. However, the preparation and stability of MOFs present limitations that researchers are actively seeking to address. By integrating MOFs into a matrix such as polymers, they can form composites with a flawless surface because the functional groups in MOFs can serve as suitable sites for forming bonds with the organic parts of the matrix to produce selective membranes for the separation of CO2 and H2 gases. They retain the exceptional features of MOFs while leveraging the unique properties of the polymer matrix, ultimately increasing gas separation performance. This review critically evaluates recent global research efforts on the selective separation of hydrogen and carbon dioxide gases, discussing the impact of various factors such as composite factors and functional groups on the separation efficiency of these two specific gases. This study also provides a brief explanation of the mechanisms of H2/CO2 separation.