Review on the synergistic effect between metal–organic frameworks and gas hydrates for CH4 storage and CO2 separation applications

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Metal–organic framework (MOF) and gas hydrate synergy is a potential technology for CH4 storage and CO2 separation. This review introduces the structural characteristics of MOFs and gas hydrates and highlights their limitations in gas storage and separation. Herein, the crystal types, pore structures, and wettability of all the MOFs used for CH4 and CO2 hydrate formation to date are summarized. The effects of different MOFs on hydrate thermodynamics, kinetics, and gas storage capacity are analyzed, along with the changes in MOF structures. Confined and bulk phase hydrates are formed in MOFs, and the CH4 hydrate phase equilibrium in MOFs show only negligible changes. Generally, the confined phase equilibrium is more severe than those in the bulk phase. In most studies on the effect of MOFs on hydrate kinetics, only the induction time has been explored, and it can be shortened by adding MOFs. Additionally, the synergistic effect of MOFs and hydrates on CH4 storage capacity forms a majority of research in this field. Hydrophobic MOFs, synergistic with hydrates, can enhance the CH4 storage capacity of MOF–hydrate systems. The MOF structure is not influenced by hydrate formation and dissociation. In the case of CO2 hydrate formation by MOFs, the number of studies is relatively few, although the corresponding results and conclusions are similar to those of CH4 hydrates. This paper highlights the research progress and challenges associated with MOF–hydrate synergy and their impact on CH4 storage and CO2 separation, unveiling new avenues for research in this direction.