Porous organic cages (POCs) have emerged as a new sub-class of porous materials that stand out by virtue of their tunability, modularity, and processability. Similar to other porous materials such as carbons, zeolites, and MOFs, the pore network formed by the interconnected cavities of POCs makes them inherently good candidates for gas capture and gas separation. However, in this review, we focus on the emerging trends in the application of POCs in the fields of clean energy and environmental sustainability, which are a result of their unique features. The structure-property relationship we attempted to extract from the case studies will provide guidance for the design of new functional POCs in the future.