A metal–organic nanotube (MONT) was assembled by bridging the truncated metal-calixarene octahedra with coordinating water molecules. Remarkably, the tubular compound exhibited a much higher sorption capacity for C₂H₆ and C₃H₈ than for CH₄, and hence represents a promising material for separating these gases. The addition of a little NiSO₄ into the reaction system led to the formation of a 2D metal-calixarene network.