Metal-organic framework-based CO2 capture: from precise material design to high-efficiency membranes

A low-carbon economy calls for CO capture technologies.Membrane separations represent an energy-efficient and environment-friendly process compared with distillations and solvent absorptions.Metal-organic frameworks(MOFs),as a novel type of porous materials,are being generated at a rapid and growing pace,which provide more opportunities for high-efficiency CO capture.In this review,we illustrate a conceptional framework from material design and membrane separation application for CO capture,and emphasize two importance themes,namely(i)design and modification of CO-philic MOF materials that targets secondary building units,pore structure,topology and hybridization and(ii)construction of crack-free membranes through chemical epitaxy growth of active building blocks,interfacial assembly,ultrathin two-dimensional nanosheet assembly and mixed-matrix integration strategies,which would give rise to the most promising membrane performances for CO capture,and be expected to overcome the bottleneck of permeability-selectivity limitations.

Metal-Organic Framework Membranes and Membrane Reactors:Versatile Separations and Intensified Processes

Metal-organic frameworks are an emerging and fascinating category of porous solids that can be self-assembled with metal-based cations linked by organic molecules.The unique features of MOFs in porosity(or surface areas),together with their diversity for chemical components and architectures,make MOFs attractive candidates in many applications.MOF membranes represent a long-term endeavor to convert MOF crystals in the lab to potentially industry-available commodities,which,as a promising alternative to distillation,provide a bright future for energy-efficient separation technologies closely related with chemicals,the environment,and energy.The membrane reactor shows a typical intensified process strategy by combining the catalytic reaction with the membrane separation in one unit.This review highlights the recent process of MOF-based membranes and the importance of MOF-based membrane reactors in relative intensified chemical processes.

ZIF-L membrane with a membrane-interlocked-support composite architecture for H/CO separation

Metal–organic framework(MOF)membranes hold great promise in energy-efficient chemical separations.The outstanding challenges of the microstructural design stem from(1)thinning of membranes to immensely reduce the mass-transfer resistance(for high permeances);(2)tuning of orientation to optimize the selective transport of gas molecules,and(3)reinforcement of intercrystalline structure to subside leakage through defective gaps(for high selectivity).Here,we propose the ZIF-L membrane that is completely confined into the voids of the alumina support through an interfacial assembly process,producing an appealing membrane-interlocked-support(MIS)composite architecture that meets the requirements of the microstructural design of MOF membranes.Consequently,the membranes show average H2 permeances of above 4000 GPU and H_(2)/CO_(2) separation factor(SF)of above 200,representing record-high separation performances of ZIF-L membranes and falling into the industrial target zone(H_(2) permeance>1000 GPU and H_(2)/CO_(2) SF>60).Furthermore,the ZIF-L membrane possessing the MIS composite architecture that is established with alumina particles as scaffolds shows mechanical stability,scraped repeatedly by a piece of silicon rubber causing no selectivity loss.