Zeolites and metal-organic frameworks (MOFs) represent an attractive class of crystalline porous materials that possesses regular pore structures. The inherent porosity of these materials has led to an increasing focus on gas separation applications, encompassing adsorption and membrane separation techniques. Here, a brief overview of the critical properties and fabrication approaches for zeolites and MOFs as adsorbents and membranes is given. The separation mechanisms, based on pore sizes and the chemical properties of nanochannels, are explored in depth, considering the distinct characteristics of adsorption and membrane separation. Recommendations for judicious selection and design of zeolites and MOFs for gas separation purposes are emphasized. By examining the similarities and differences between the roles of nanoporous materials as adsorbents and membranes, the feasibility of zeolites and MOFs from adsorption separation to membrane separation is discussed. With the rapid development of zeolites and MOFs towards adsorption and membrane separation, challenges and perspectives of this cutting-edge area are also addressed.