Front. chem. Front. chem. Synthesis and Characterization of Covalent Triazine Framework CTF-1@Polysulfone Mixed Matrix Membranes and Their Gas Separation Studies Dey Subarna Bügel Stefanie Sorribas Sara Nuhnen Alexander Bhunia Asamanjoy Coronas Joaquín Universidad de Zaragoza Janiak Christoph 2019 research-article