CO2 capture from flue gas has to be considered under stringent process conditions such as availability of flue gas (post combustion) at elevated temp and near atmospheric pressure, low CO2 partial pressure in flue gas, competitive adsorption by contaminants such as H2O, SOx/NOx . The CO2 capacity and CO2/N2 selectivity of known MOFs are not very promising at low pressure. Other important issues involved are questionable long term structural stability of MOF materials, high cost of even the most basic of organic linkers , challenges in robust formulations of MOF etc.
Despite tall claims in scientific literature close scrutiny suggests otherwise!
So far these are the limitations for MOF to do CO2-PSA, and little far expensive than conventional adsorbent. We can hope one day somebody comes with a good adsorbent, therefore we need to do more research on this area.
Use of fine organic molecules as linkers in MOF synthesis will definitely not work considering the huge scale of the targeted separation. Majority of research in this area are focused on synthesis/characterization of MOFs made with exotic linkers and their testing in milligram scale for CO2 adsorption. Such materials does not have much value as practical CO2 adsorbent. The research focus should be in the development of MOFs based on cheap linkers (from biological source!?)!
As of now activated carbon based adsorbents seems to be of far better choice than MOFs.
So far I think the most promising use of MOFs are in CO2 separation and catalysis rather than in gas storage, mostly because of the reasons mentioned above, but also due to most MOFs being relatively unstable for long term storage ie. more than 20 years. However, I think we are only scratching the surface of what can be done with MOFs and we will see new applications emerging in the next 5 years.
Petrochemical derived organic acid based MOF linkers are costly. It will be useful if we can extract such molecules from natural sources!
Yes, not only with MOFs but by doing some kind of incorporation with MOFs there may be chances, for that we have to wait some more years.
A comment about the costs of linkers. One of the reasons for the high costs is that very few companies actually compete in the synthesis meaning that in reality a monopoly exists on the supply side. Secondly, so far the demand for such linkers is in general quite low as in research one often talks of gram scale rather than tons which would be necessary for industrial applications.
If you need to be convinced otherwise I would look at the price of carbon nanotubes as an example of "molecules" that were very expensive, but due to a rise in demand and more competition on the supply side have been largely reduced in price over the last 10 years. I'm not saying this would automatically happen for MOF or MOF-linkers, but I do not think costs will be a highly decisive factor in the "make-or-break" of their industrial application.
In the context of CO2 removal from power plant flue gas by P/VSA, activated carbon (derived from biomass waste) in combination with zeolite, silica gel in a layered bed configuration seems to be a far better choice than MOFs. For this large scale separation the adsorbent must be cheap, structurally robust and readily available/scalable with suitable surface properties (e.g. reasonable CO2/N2 selectivity, reasonable CO2 working capacity, favorable CO2 and H2O desorption kinetics etc.) to handle flue gas composition. However MOF may find better application as catalyst or adsorbent in the area of fine chemical production/separation!
Generally, MOF materials are not suitable for CO2 capturing from flue gas by using TSA. As others mentioned above, MOF science is still infant and is limited to laboratory-scale not industrial scale. there is no supplier (except sigma-Aldrich) that can provide MOF in large scale. most of the MOF's are not stable in water, therefore they are not suitable for CO2 capturing from flue gas which contains between 5-15% H2O. Heat of adsorption of CO2 is also another critical parameter for industrial usage of the adsorbent. Usually, MOFs show their extraordinary capacity of adsorption at higher pressures which is not suitable for low pressure flue gas feed. The cost of the linkers are extremely expensive. however, I hope in near future, we can find a solution how to scale upping the MOFs production in water media instead of expensive and toxic solvents like DMF.
We are the group working in MOFs and I am working in MOF field for the last 10 years. I do modelling on understanding adsorption and diffusion of gases in MOFs for adsorbent and membrane applications. As far I know MOFs has several limitations to drive to industrial market. One of the major issue is the stability which I think people started to explore more on developing MOFs with better stability. Second is the scale-up issue which we already started to explore using flow-chem and trying to upscale further. For reference have a look at the recent publication in Nature Scientific Reports
Versatile, High Quality and Scalable Continuous Flow Production of Metal-Organic Frameworks, Scientific Reports, Volume:4,Article number:5443, DOI:doi:10.1038/srep05443.
We also done lot of work on CO2 capture using adsorbent and membrane.
Happy to answer any queries related to it and probably explore more opportunity for collaboration.
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