In this work, mixed-matrix membranes comprising Zn(pyrz)(2)(SiF6) (or SIFSIX-3-Zn) metal-organic framework were fabricated for potential applications in biogas upgrading and post-combustion CO2 capture. First, submicron-sized Zn(pyrz)(2)(SiF6) crystals that selectively adsorb and transport CO2 over CH4 and N-2 were synthesized by a facile sonochemical method. Then, high-quality mixed-matrix membranes free of filler/polymer interfacial voids were succesfully fabricated by employing crosslinked polyethylene oxide as a polymer matrix. CO2/CH4 and CO2/N-2 mixture gas permeation tests revealed that the separation properties of mixed-matrix membranes, especially selectivities, were significantly improved compared to those of pure polymeric membrane owing to the selective CO2 uptake and transport in Zn (pyrz)(2)(SiF6) crystals. (C) 2015 Elsevier B.V. All rights reserved.