Enhanced selectivity in mixed matrix membranes for CO2 capture through efficient dispersion of amine-functionalized MOF nanoparticles

Abstract

17Mixed Matrix Membranes (MMMs) for gas separation applications, have enhanced selectivity when 18 compared with the pure polymer matrix, but are commonly reported with low intrinsic permeability, 30The current default technology for large scale CO 2 capture and storage (CCS) is based on liquid 31 phase absorption towers; whilst many projects of this sort are proposed, few reach completion as 32 costs become prohibitive 3 . Therefore, it is imperative to offer more cost-effective technological 33 solutions. Membrane separation is often considered; however, current commercial membrane 34 technologies are virtually as expensive as adsorption technologies. This is because gas fluxes 35 through selective membranes are so low that hundreds of millions of m 2 of commercial membranes 36 are required even for a single 1000MW power station 5 . When combined with membrane costs of 37 ~$50/m 2 , the capital cost for commercial membrane based solutions to CCS is not that different 38 from the unpalatably high costs of adsorption towers for CCS. The key to a future membrane based 39 2 CCS solution lies in significantly reducing the total membrane areas required, which in turn 40 requires cheap, higher permeability membrane materials that retain a high selectivity. New research 41 is aimed at developing better performance polymers (in selectivity and permeability); however the 42 timelines for reducing costs of such polymers may not be compatible with needs to find immediate 43 candidate materials for large scale membrane based CCS solutions. 44Typically, commercial membrane materials have low permeability of a few tens of Barrers 45(1 Barrer = 10 10 cm 3 (STP) cm cm 2 s 1 cmHg 1 ), but have acceptable selectivity for CO 2 removal 46 from flue-stack or natural gas sources. Merkel and co-workers 5 have shown it is imperative to 47 generate materials with orders-of-magnitude enhanced permeability whilst maintaining such 48 selectivity, to cost-effectively process the massive volumes of flue gas in power plants. 49 Microporous materials used for membrane technology potentially include inorganic and organic 50 frameworks, such as zeolites 7 , metal-organic frameworks (MOFs) 8 and covalent organic 51 frameworks 9 . However, commercial membranes units contain thin films of the selective material 52 where practical processability and physical durability requirements tend to favor the use of tough 53 polymeric thin films. Gas transport in most polymers can be explained with the solution diffusion 54 model, where the permeability coefficient (P) is a product of solubility (S) and diffusion coefficient 5510 . Polymers of Intrinsic Microporosity (PIMs) 11,12 , are a sub-class of microporous polymers 56 with a rigid, contorted backbone structure (for example, PIM-1 in Figure 1) and high intrinsic 57 permeabilities (e.g. P CO2 ~ 3000 Barrer), but with low selectivity compared to commercial polymers 58 (30-50 for CO 2 /N 2 separations) 13 . Thermal and other post-processing of PIM-1 and other polymers 59 such as TR-polymers 14 leads ...

Improved gas transport properties of polyurethane–urea membranes through incorporating a cadmium‐based metal organic framework

“…However, in several other publications, it was reported that the addition of inorganic fillers (e.g., metal oxides such as ZnO, silica, alumina, and TiO 2 ) to the PU matrix led to higher selectivities but lower permeabilities . Interestingly, the incorporation of functionalized‐MOFs in PU membranes was found to increase the CO 2 /N 2 selectivity but not to change the CO 2 permeability appreciably . Incorporation of 20 wt % SAPO‐34 into the PU increased the CO 2 /N 2 selectivity by 37% but decreased the CO 2 permeability by about 4%.…”

“…Additionally, high surface area and excellent dispersibility of MOFs in the most polymers have led to an improvement in the gas permeability, selectivity, or both . PIM‐UiO66 membranes with different ligands and particle sizes were developed . The membrane embedded with NH 2 ‐UiO66 showed the highest enhancement in CO 2 /N 2 selectivity with a minimal loss in the permeability.…”

Mass transport through metal organic framework membranes

“…Theoretically, MOFs are capable of mitigating the trade-off phenomenon between permeability and selectivity due to the crystal structure and porosity [67,68]. It is accepted that the MOF-based mixed matrix membranes (MMMs) [69][70][71][72][73], which refer to the composite membranes with MOF powder fillers dispersed in polymer matrix, possess most promise for practical separation applications. But their permeability is lower compared to the pure MOF membranes caused by the nonporous polymer matrix [74][75][76].…”

In Situ Growth of Zeolitic Imidazolate Framework‐67‐derived Nanoporous Carbon@K0.5Mn2O4 for High‐Performance 2.4 V Aqueous Asymmetric Supercapacitors

“…[29,30] Owing to their large surfacea rea,p orous inner structure and tunable pore size, [31] MOFs have been widely used in catalysis, [32] gas adsorption and desorption, [33,34] sensing, [35] drug deliverya nd optoelectronics. [29,30] Owing to their large surfacea rea,p orous inner structure and tunable pore size, [31] MOFs have been widely used in catalysis, [32] gas adsorption and desorption, [33,34] sensing, [35] drug deliverya nd optoelectronics.…”