A porous material structure and device are described and shown to enhance the mass transfer and/or heat transfer at low pressure drops for removal of certain molecular species from a fluid by adsorption and/or catalytic reaction. The porous structure of active materials comprising packed fine particles of adsorbents or catalysts is encapsulated with a thin membrane to provide large interfacing area with the fluid per unit volume for rapid mass transfer between the porous structure and fluid. The thin membrane also blocks particulate from getting into the porous structure of the active material. For the process involving significant heat of adsorption and/or reaction, the another surface of the porous structure of the active material is encapsulated with a thin non-permeable sheet to interface with a thermal fluid for rapid heat transfer between the porous structure and the thermal fluid. The device can be used for removal of CO2, moisture, and hydrocarbon molecules from a gas stream with rapid in-situ regeneration. The device can be used for removal of water from water-containing liquid fluids, such as solvents and oils. The device can be used for removal of bacteria, virus, salts, and molecular contaminants from one water simultaneously.