Novel waste treatment methods and dependable alternative energy sources must keep up with the world’s rapid population growth, urbanization’s higher living standards, and the concurrent escalation of socio-economic activities. Porous carbon materials hold the potential to be a significant contributor in both of these domains because of their proven efficiency in wastewater treatment, gas separation, and storage. In today’s water-energy nexus, there is a greater urgency to develop environmentally sustainable processes to treat contaminated water before discharge. These materials possess a controllable, nano-scale or micro-scale pore structure throughout the surface. The porous structure of carbon typically makes it an efficient filtration medium that can be applied as the support structure of membrane separation. On the other hand, significant efforts have been made over the last decade to develop low-cost, simple-to-use, and easy-to-scale porous carbon materials and composites for the production of clean and sustainable energy due to their larger surface area, rapid transport of active sites, and availability of active sites at various length scales. Additionally, they have the advantages of a variable specific surface, programmable pore structure, solid physicochemical stability, simple functionalization, and the potential to improve performance depending on the applications. Typical gas storage applications include fuel gases for automobiles, therapeutic medical gases for clinical purposes; instrument gases for industries; natural gas for long-distance transportation, and electronic gas delivery for semiconductor fabrication processes. The application of porous carbon material in water treatment and remediation and its efficiency in mechanical stability, chemical stability, permeability, and resistance to fouling will be thoroughly discussed in this book chapter. This chapter also includes an in-depth review of porous carbon materials for gas separation and storage. Even the prospects of porous carbon materials with regard to these applications will be discussed in detail.