Methane capture with α-cyclodextrins

α-cyclodextrin dissolved in water binds methane giving crystals of a 1 : 1 complex in up to 57% yield. The binding constant was K a = 21 (± 1.0) M −1 . 3 A ,6 A ,3 D ,6 D -dianhydro-α-cyclodextrin which has a smaller cavity than α-cyclodextrin binds methane three fold better ( K a = 75 (± 25) M −1 ) α-cyclodextrin forms a crystalline 1 : 1 complex with methane that release the gas upon addition of water.