ChE Seminar – “Energy Efficient Separations using Metal–Organic Framework Membranes and Adsorbents” by Dr. Jonathan Bachman
Large-scale purification of chemicals and fuels has historically been achieved using energy-intensive thermally-driven distillation and scrubbing processes. With the recent development of metal–organic frameworks, a class of microporous adsorbents with unique pore structures and functionalities, we now have an opportunity to revisit and reinvent chemical separations. The M2(dobdc) (MOF-74; M = Mg, Mn, Fe, Co, Ni, Zn; dobdc4- = 2,5-dioxido-1,4-benzenedicarboxylate) family of frameworks is particularly promising due to coordinatively unsaturated metal sites that display selective gas-metal interactions. I will first discuss membrane-based separations and show how M2(dobdc) nanocrystals can be incorporated into polymer matrices to form mixed-matrix membranes with exceptional improvements in ethylene permeability, ethylene/ethane selectivity, chemical stability, and plasticization resistance originating from the presence of coordinatively unsaturated metal sites. I will then go on to show that a framework isomer, M2(m-dobdc) (m-dobdc = 4,6-dioxido-1,3-benzenedicarboxylate), can dramatically improve ethylene- and propylene-separation through a detailed investigation of adsorption thermodynamics that elucidate useful trends metal-gas interaction energies. Together, these works highlight the power of combining materials design with gas transport and adsorption thermodynamics to produce new technologies for energy-efficient separations.