This review compares the different types of membrane processes for air dehumidification. Three main categories of membrane-based dehumidification are identified – membrane contactors using porous membranes with concentrated liquid desiccants

separative membranes using dense membrane morphology with a pressure gradient to drive the separation of moisture from air

and adsorptive membranes using nanofibrous membranes which adsorb and capture moisture to realise dehumidification. Drawing upon the importance of dehumidification and humidity control for urban sustainability and energy efficacy

this review critically analyses and recognizes the three unique categories of membrane-based air dehumidification technologies. Essentially

the discussion is broken into three sections-one for each category-discriminating in terms of the driving force

membrane structure and properties

and its performance indicators. Readers will notice that despite having the same objective to dehumidify air

the polymers used amongst each category differs to suit the operating requirements and optimize dehumidification performance. At the end of each section

a performance table or summary of dehumidifying membranes in its class is provided. The final section concludes with a comparative review of the three categories on membrane-based air dehumidification technologies and draw inspiration from parallel research to rationalise the potential and innovative use of promising materials in membrane fabrication for air dehumidification.