In this paper the separation of the binary mixture H-2/CH4 on (i) neat supported ZIF (zeolitic imidazolate framework) membranes of types ZIF-8 and ZIF-90, (ii) a neat supported Matrimicl polymer membrane, and (iii) Mixed Matiix Membranes (MMMs) with 10, 20 and 30 vol-% ZIF-8 and ZIF-90 nanociystals in Matrimid is compared. A high separation performance was found surprisingly for the MMMs and it was concluded that the polymer matrix prevents the framework flexibility of the embedded Metal Organic Framework (MOF) particles, thus increasing the selectivity of MMMs with particle loadings <= 20 vol-%. Higher loadings, however, lead to agglomerations and segregations, which result in MMMs with lower selectivities. To approve the idea of the hindered linker distortion caused by the surrounding polymer, we coated the top of neat supported ZIF-8 and neat ZIF-90 membranes with an additional Matrimid polymer layer (dual-layer membrane). Indeed, the polymer coating also caused a suppression of the linker distortion of the ZIF layer in contact with the polymer which results in an enhanced H-2/CH4 selectivity. (C) 2015 Elsevier B.V. All rights reserved.