State of the art, challenges and prospects in metal–organic frameworks for the separation of binary propylene/propane mixtures

Propylene (C3H6) as one of the most crucial raw chemical materials has been widely used in the chemical industry. The high-purity C3H6 (higher than 99.5 %) is in great demand for producing polypropylene or other chemical products. C3H6 is nevertheless mostly produced by steam cracking naphtha or dry gas refining and is invariably blended with minor impurity gases like propane (C3H8). At present, the petrochemical industry depends almost exclusively on the heat-driven cryogenic distillation process for C3H6 purification. However, both C3H6 and C3H8 molecules have very similar physical properties (such as kinetic diameter, boiling point, polarity, etc.), which makes conventional cryogenic distillation inefficient and energy-intensive. To decrease energy consumption, cost-efficient, and tend to be environmentally friendly, adsorptive-based separation using porous materials is expected to accomplish C3H6 purification from C3H6/C3H8 mixtures under ambient conditions. In particular, metal–organic frameworks (MOFs) with high porosity, regular adjustable pore shape and pore environment have promising advantages as porous adsorbents for C3H6 purification. This thesis provides an in-depth review of the present MOF materials that show promise for the separation of C3H6/C3H8 mixtures using adsorptive technology. It focuses particularly on recent developments in the usage of MOFs to achieve reversed C3H6/C3H8 separation. Meanwhile, we interpret the separation mechanism and further classify the relevant mechanisms of flexible materials, then we also summarize the separation research methods, and related techniques. Ultimately, we propose a bold conjecture regarding the future perspectives and urgent problems in the exploitation of MOFs for C3H6 purification in industry and the academic community and give possible development directions.