“…[46] Also, the group of Caro described the successful preparation of zeolite imidazolate framework (ZIF)-type membranes, which are applied in the separation of hydrogen from other gases. [47,48] Very recently, the potential of ZIF membranes for CO 2 removal has been demonstrated. [49] In view of the gases molecular dimensions (2.9, 3.3, 3.6, and 3.8 for H 2 , CO 2 , N 2 , and CH 4 , respectively), this selectivity should be a result of molecular sieving by the pore apertures of MOF structures (pore size 3-4 ).…”