A gas separation unit for the separation of carbon dioxide from air is proposed for use in a cyclic adsorption/desorption process and using a loose particulate sorbent material. Sorbent material is arranged in at least two stacked layers, and each layer comprises two sheets of a flexible fabric material which is gas permeable but impermeable to the loose sorbent material. The sheets are arranged parallel defining an inlet face and an outlet face, are arranged with a distance in the range of 0.5-2.5 cm, and are enclosing a cavity in which the sorbent material is located. Said layers are arranged in the unit such that the inflow passes through the inlet face, subsequently through the particular sorbent material located in the cavity of the respective layer, subsequently to exit the layer through the outlet face to form the gas outflow.