Clean water and clean energy are vital for human activity and socio-economic development. Hong Kong suffers from severe water scarcity, and membrane technology is expected to play a critical role to supplement the existing water supply. However, the current membranes for water production and water reuse, like reverse osmosis (RO) and nanofiltration (NF) are constrained by their relatively low water permeance (which affects energy consumption) and low selectivity (which affects product quality). Therefore, the membrane itself as the “chip” of the membrane process should be greatly emphasized and fine tailored for more effective clean water supply and clean energy generation.