Elevated pervaporation performance of polysiloxane membrane using channels and active sites of metal organic framework CuBTC

Hybrid membranes with polydimethyl siloxane (PDMS) as the polymer matrix and metal organic framework (MOF) CuBTC ([Cu3(BTC)2]) as the filler were fabricated and applied in pervaporative separation of thiophene from model gasoline. CuBTC submicroparticles with size of 0.2-0.3 μm were synthesized through a facile method at room temperature. The morphology, crystal structure and pore parameters of CuBTC, together with the morphology, functional groups, thermal and mechanical property, free volume characteristics, sorption and separation performance of PDMS-CuBTC hybrid membranes were studied. Primary functions of CuBTC particles are summarized as follows: (i) the channels of CuBTC provide expressways with low resistance for the transport of permeates; (ii) the submicroparticles interfere with the packing of PDMS chains, generating extra free volume of the membrane; (iii) the active metal sites of CuBTC facilitate the transport of thiophene; and (iv) the channels of CuBTC sieve thiophene from the bulk of model gasoline. As a result, the normalized flux and selectivity of PDMS membranes are elevated simultaneously. The optimal separation performance is achieved when the weight ratio of normal CuBTC to PDMS reaches 8%, with a permeation flux of 194.2 kg μm/(m2 h) and an enrichment factor of 5.2 (increase by 100% and 75% compared with PDMS control membrane, respectively).