Study On The Preparation Of F-Ce Nanosheet Mixed Matrix Membrane And The Separation Performance Of CO₂

The excessive emission of CO₂ resulted in greenhouse effect which do harm to human production and living and the ecological environment.The search for efficient carbon capture technologies has become one the hot research topic.Membrane gas separation technology has attracted wide attention due to its low energy consumption and easy operation.In this study,a novel porous two-dimensional nanomaterial cerium fluoride nanosheet?F-Ce?was used as the key material to prepare a mixed matrix membrane.Ionic liquid 1-ethyl-3-methylimidazole thiocyanate was successfully decorated on F-Ce nanosheets,and basic group functionalized F-Ce nanosheets?f-F-Ce nanosheets?were synthesized to fabricate mixed matrix membranes.Through the enhancement of membrane interface,bulk,channel regulation and gas transport mechanism,the membrane permeability and selectivity of the membrane were improved synergistically.The findings were as follows:Interlayer transport:A new type of porous two-dimensional nanomaterial F-Ce nanosheets was used as a filler for the first time,and it was introduced into a block polyetheramide?Pebax?1657?to fabricate a series of mixed matrix membranes?MMMs?.The F-Ce nanosheets possessed the porous structure,which improved the gas transport.The interlayer spacing size of 0.344 nm could achieve accurate sieving CO₂gas,which resulted in the simultaneous enhancements both in permeability and selectivity.F-Ce nanosheets showed good interfacial compatibility with the polymer matrix,which significantly improved the mechanical strength of the Pebax/F-Ce MMMs.The MMMs exhibited a 2.6 fold in Young's modulus and 1.5 fold in break strength of pristine Pebax membrane.The unique structure and excellent performance of F-Ce nanosheets construct CO₂-promoted transport channels at the polymer-filler interface.Pebax/F-Ce MMMs have significantly improved gas separation performance in both dry and humidified states.In the humidified state,the Pebax/F-Ce-8%membrane showed the CO₂ permeability of 1508 Barrer and CO₂/CH₄ selectivity of 37,which exceeds the 2008 Robeson upper bound.Solubility-diffusivity mechanism intensification:Ideal channels should possess both appropriate separation size to achieve CO₂ sieving and good CO₂ affinity,and to promote synergistic strengthening of the solution-diffusion mechanism.In our work,1-ethyl-3-methylimidazole thiocyanate was successfully decorated on F-Ce nanosheets to synthesize basic functionalized F-Ce nanosheets?f-F-Ce?.The introduction of basic groups can provide affinity sites in the membrane to facilitate CO₂ transport,which resulted in the enhancement of solution characteristics of MMMs.Compared to Pebax/F-Ce mixed matrix membrane,the gas permeability of Pebax/f-F-Ce mixed matrix membrane was significantly improved.In the humidified state,the Pebax/f-F-Ce-8%membrane showed a CO₂ permeability of 1823 Barrer and a CO₂/CH₄selectivity of 35,which exceeded the 2008 Robeson upper bound.