Contents lists available at ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur CO 2 /N 2 gas separation using Fe(BTC)-based mixed matrix membranes: A view on the adsorptive and filler properties of metal-organic frameworks Ana Rita Nabais a , Rui P.P.L. Ribeiro a , José P.B. Mota a , Vítor D. Alves b , Isabel A.A.C. Esteves a, ⁎ , Luísa A. Neves a, ⁎ a LAQV – REQUIMTE, Departamento de Qúímica, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Caparica 2829-516, Portugal b LEAF, Linking Landscape, Environment, Agriculture and Food, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, Lisboa 1349-017, Portugal ABSTRACT The incorporation of a Metal-Organic Framework (MOF), Fe(BTC), into a polymeric membrane was assessed for CO 2 /N 2 gas separation. The adsorptive and filler properties of the MOF in the Mixed Matrix Membranes (MMMs) produced were investigated as a strategy to separate CO 2 from N 2 and contribute to reduce CO 2 emissions. Therefore, Fe(BTC) was firstly characterized by single-component adsorption equilibria measurements of CO 2 and N 2 , to evaluate the MOF performance as an adsorbent for CO 2 /N 2 separation and its adsorption role in the MMMs performance. Fe(BTC) was then incorporated in Matrimid®5218 at different loading percentages, and the MMMs produced were characterized by distinct techniques (SEM, TGA, puncture tests and contact angle essays). Finally, pure gas permeation experiments were carried out for CO 2 and N 2 at 303 K, 323 K and 353 K, to evaluate the temperature impact on both gas permeability and CO 2 /N 2 ideal selectivity. The results show that an increase in CO 2 permeability and CO 2 /N 2 ideal selectivity can be advantageously achieved, especially at the higher operating temperature of 353 K. At these conditions, the Robeson upper-bound is surpassed, which is a clear indication of the high potential of using Matrimid®5218/Fe(BTC) MMMs in post-combustion streams at high- temperatures. 1. Introduction The implementation of a carbon dioxide (CO 2 ) capture and storage (CCS) technology, at a large scale, is a promising strategy to reduce CO 2 emissions. The major challenge to commercialize CCS technology at a large scale is the energy cost associated with the separation method [1]. Currently available technologies for CO 2 separation are based on ab- sorption using aqueous solutions of amines (e.g. MEA), adsorption and cryogenic distillation [2]. Over the years, membrane gas separation technology has emerged as an alternative to the conventional methods used to separate/remove gases. Gas separation using membranes have a lower maintenance cost, do not require additives, and, when using dense membranes, the dis- tinct solubility and diffusivity of the gaseous species involved, con- tribute to the efficiency of the gas separation [3,4]. Gas separation through membranes is typically based on the shape and size of the molecules to be separated and on their interaction with the membrane material [5]. Besides the specific characteristics required for specific applications, understanding the influence of temperature on gas se- paration performance, is essential to understand the influence of polymer chemistry and structure on thermally activated transport processes [6]. Polymer membranes are industrially used to remove carbon dioxide from natural gas, to separate nitrogen from air, to remove hydrogen from mixtures in petrochemical processing applications [7], among other applications [8–10]. This class of membranes is the most com- monly used in industrial processes due to their easy processing, effi- ciency and mechanical resistance. However, one of the major draw- backs when using membrane gas separation technology is the trade-off relationship between permeability and selectivity, since more perme- able membranes tend to be less selective, and vice-versa [11,12]. Therefore, there is a great need for new materials to answer this chal- lenge. Mixed matrix membranes (MMMs) comprising inorganic fillers (e.g. zeolites [13–15], carbon nanotubes [16,17], carbon molecular sieves [18,19], and metal-organic frameworks [3,20]) dispersed in a poly- meric matrix may provide an interesting alternative to improve the gas separation performance of polymeric membranes. Metal-Organic Frameworks (MOFs) are a class of organic-inorganic porous materials, comprised of ordered networks formed by organic https://doi.org/10.1016/j.seppur.2018.03.028 Received 14 February 2018; Received in revised form 14 March 2018; Accepted 14 March 2018 ⁎ Corresponding author. E-mail addresses: iaesteves@fct.unl.pt (I.A.A.C. Esteves), lan11892@fct.unl.pt (L.A. Neves). Separation and Purification Technology 202 (2018) 174–184 Available online 26 March 2018 1383-5866/ © 2018 Elsevier B.V. All rights reserved. T