A gas separation unit for the separation of a first gas, preferably carbon dioxide, from a mixture containing said first gas as well as further gases different from the first gas, by using a cyclic adsorption/desorption process using a loose particulate sorbent material for gas adsorption, wherein said particulate sorbent material is arranged in at least two stacked layers, wherein each layer comprises two sheets of a flexible fabric material which flexible fabric material is gas permeable but impermeable to the loose particulate sorbent material, which sheets are arranged essentially parallel defining an inlet face of the layer and an outlet face of the layer, which sheets are arranged with a distance in the range of 0.3-11 cm or 0.3-5 cm, and which sheets are mounted on a rectangular circumferential frame structure, said rectangular frame structure including four metal profiles arranged pairwise mutually parallel, one pair along a longitudinal direction and one pair along a transverse direction, with respect to the airflow through the gas separation unit, and said frame structure enclosing, together with said sheets of flexible fabric material a cavity in which the particulate sorbent material is located, wherein primary heat exchange piping, as part of the metal profiles (16, 13) or as separate elements, is arranged on the two lateral outer edges of the layer, preferably within the cavity, extending along said longitudinal direction, said primary heat exchange piping comprising at least one first lateral outer edge heat exchange piping at a first lateral side of the rectangular frame structure with at least one heat exchange fluid inlet and at least two or a plurality of heat exchange fluid outlets, and at least one second lateral outer edge heat exchange piping at a second lateral side of the rectangular frame structure comprising at least two or a plurality of heat exchange fluid inlets and at least one heat exchange fluid outlet, wherein at least one essentially parallel array of secondary heat exchange pipes (5, 6) is provided within the cavity, each secondary heat exchange pipe fluidly connecting a first lateral outer edge heat exchange piping with a second lateral outer edge heat exchange piping, said secondary heat exchange pipes (5, 6) extending along said transverse direction and being spaced at a distance (a), along said longitudinal direction, in the range of 0.5-5 cm; wherein the first outer diameter (p) of the secondary heat exchange pipes (5, 6) in a direction perpendicular to the plane of the layer is at least twice as large as the second outer diameter (q) of the secondary heat exchange pipes (5, 6) in the longitudinal direction wherein said secondary heat exchange pipes (5, 6) are in thermal contact with sheets of metal which are arranged essentially perpendicular to the main plane of the frame, and which extend oscillating between pairwise adjacent secondary heat exchange pipes (5, 6) either over the complete transverse distance or at least partially and/or section-wise between the first side and secondary side primary heat exchange piping (1, 4) and thereby contacting the secondary heat exchange pipes for thermal contact at a plurality of contact points or said secondary heat exchange pipes (5, 6) are held in place with spacers which are arranged essentially perpendicular to the main plane of the frame, and which at least extend between pairwise adjacent secondary heat exchange pipes (5, 6) and wherein the secondary heat exchange pipes (5, 6) comprise a narrow central portion with a diameter (c) in the range of 0.5-3 mm, and at both ends a widened portion with bulging portions extending beyond the surface of the narrow central portion and providing an end surface, and wherein the height (b) of the sheets of metal or of the spacers is essentially the same or smaller than length of the narrow central portion in a direction perpendicular to the plane of the layer, wherein the unit has a gas inlet side or gas inlet manifold through which an inflow of gas mixture enters the unit and a gas outlet side or gas outlet manifold through which a gas outflow exits the unit, the gas pathway between the inflow and the outflow being confined in the unit to pass through at least one layer; wherein 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 respective layer through the outlet face to form the gas outflow; wherein the layers are arranged such that inlet faces of adjacent layers are facing each other enclosing gas inlet channels and such that outlet faces are facing each other enclosing gas outlet channels; wherein the mean distance between inlet faces and/or outlet faces defining said channels (53, 81), measured in a direction essentially perpendicular to a main gas inflow direction and a main gas outflow direction, respectively, is in the range of 0.5 - 25 cm or 0.5 - 15 cm. which flexible fabric material is gas permeable but impermeable to the loose particulate sorbent material, which sheets are arranged essentially parallel defining an inlet face of the layer and an outlet face of the layer, which sheets are arranged with a distance in the range of 0.3-11 cm or 0.3-5 cm, and which sheets are mounted on a rectangular circumferential frame structure,