As the promising materials to address global issues of clean energy technologies, and environmental sustainability, the emerging class of crystalline microporous materials, porous coordination polymers (PCPs) or metal-organic frameworks (MOFs), have been applied in fields of gas storage and separation, delivery vessel, sensors, catalysis, supercapacitors, FETs, batteries, proton conduction, and so on. We have found the 3rd generation (3G) PCPs/MOFs (Soft porous crystals, SPCs) that possess flexible or dynamic porous frameworks and reversibly respond to external stimuli, not only chemical but also physical, unlike robust PCPs/MOFs (2G). In this talk, the chemistry, current features, and prospects of 3G - 4G materials, especially the theoretical interpretation of the design, function, and mechanism of the dynamic structure, will be mentioned essentially and straightforwardly, using the recent successful results of water isotopologue separation as an example.