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New MOF Methane Storage Material Exceeds DOE Goals for Adsorbed Natural Gas Storage by 28%

A nano-sized crystalline cage that shows promise as a superior storage material for methane. Click to enlarge. Courtesy of Shengqian Ma, Miami University.

Researchers have developed a new metal-organic framework (MOF) material with what they believe to be the highest methane storage capacity yet measured. Methane adsorption studies of the new material—PCN-14—at 290 K (16.9°C or 62°F) and 35 bar show an absolute methane-adsorption capacity of 230 v/v (standard temperature and pressure equivalent volume of methane per volume of the adsorbent material), 28% higher than the US Department of Energy (DOE) target (180 v/v) for on-board methane storage.

The PCN-14 compound, composed of clusters of nano-sized cages, has a high surface area of 2,176 m2/g and a pore volume of 0.87 cm3/g. Hong-Cai Zhou and colleagues describe the development of PCN-14 in an report in the 23 January edition of the Journal of the American Chemical Society.

The DOE has established a target for on-board methane storage at 180 v/v under 35 bar, near ambient temperature, with the energy density of adsorbed natural gas (ANG) being comparable to that of compressed natural gas (CNG) used in current practice.

A number of different types of porous materials have been evaluated for ANG storage, but until last year, no material had hit the 180 v/v target. In February 2007, researchers at the University of Missouri-Columbia (MU) and Midwest Research Institute (MRI) in Kansas City created carbon briquettes with complex nanopores capable of storing natural gas with 180 v/v. (Earlier post.)

Metal-organic frameworks (MOFs) are a relatively new class of nano-porous material that show promise for gaseous storage applications—hydrogen, methane, CO2, etc.—because of their tunable pore size and functionality. MOF compounds consist of metal-oxide clusters connected by organic linkers.

The researchers first developed an anthracene-based ultramicroporous MOF (PCN-13, PCN stands for Porous Coordination Network), but it had very limited methane uptake because of its confined pore size.

To enlarge the pore size and to continue our theme of building metal-organic frameworks containing nanoscopic coordination cages for gas storage, we have adopted a new ligand, 5,5'-(9,10-anthracenediyl)di-isophthalate (adip). Under solvothermal reaction conditions, the reaction between H4adip and Cu(NO3)2 gave rise to a porous MOF designated PCN-14.

The work was supported by the Department of Energy and the National Science Foundation.




This is good news. Adsorbed natural gas can be one way to use less oil. Since methane can be created by gasifying biomass and we all ready have the transport pipelines, this makes it even more viable.


Seems like a solution in search of a problem. I see CNG cars & buses everywhere.

Rafael Seidl

@ DS -

not sure where you are located, but CNG only accounts for a tiny fraction of the total automotive market. The cost overhead of compressing and storing natural gas at 200-300 atmospheres is substantial.

ANG can make do with the pressure already present in natural gas trunk lines. It also offers much greater flexibility wrt the shape of the tank because the mechanical stresses are much lower. Finally, the adsorption material could perhaps double as soundproofing, reducing the weight penalty associated with running on natural gas.


CNG isn't making much of a dent in the American market.
It is however making significant impacts in Asian markets.

Brian P

What's this stuff weigh relative to the weight of the gas being stored, and what's the energy density in terms of total volume?

CNG requires heavy steel tanks because of the high pressure involved, and the energy required to compress the gas is significant. The overall weight of a lighter tank with this stuff inside might be less than that of a steel tank with ordinary CNG, but even if there is not a weight advantage, there's a big advantage if further compression beyond standard natural gas supply pressure is not required.

CNG is somewhat available around here, but the big advantage if further compression is not required is that the vehicle could be simply connected to the standard gas supply in your house.

Herm Perez

LNG gets about the same mileage as gasoline on a volume basis.. it does burn very clean and there used to be a nice cost advantage.. I think not anymore...


Very good for city cars, better still if hybridized.
Good also for city buses ".
My understanding is there is a lot of gas around, so we could be in business here - or with some gas adsorption system if this one proves impractical.
Could be important.


I hybrid running adsorbed CNG would be very good, nice and clean and efficient.
Even if you have to put a 500 psi compressor in your garage, the cost would be less than a 5000 psi compressor. More than half the homes in the U.S. are heated with natural gas, but only use 20% of the natural gas consumed. Your house uses more natural gas year around than your HEV would driving 20k miles per year. So if half the cars were HEV CNG we would only increase the NG usage 10% nationwide.


I kinda got the sums right but I cant tell you as the conversions from cu ft - M3 back to btu-cuft and us gallons -cuft -litres ! But its somewhere the otherside of Mars.
You dont really want know do you?
How does the energy density compare?
At standard pressure,and temp. At a guess 1 bar. Guess 16.9oC
At 35 atmospheres just over 500psi, stores 230 times the volume (weight) at the same (standard) temp.
Or concentrated 230 times at just over 500psi.

A bit more to go to get accurate.
NG 1000 -1100btu's per ft3 .353357 M3
CNG 32,154 BTU,s per us gallon @3,000 psi 210 atm
LNG 83,000 BTU,s per us gallon @ minus 162oC
1 gall gasoline equivalent to 100ft3

Personally I prefer the metric system


A therm is 100 cubic feet at 1 atmosphere and about 100k BTU per therm. Gasoline is more than 100k BTU per gallon, but natural gas has higher octane. Right now, natural gas wholesales for about 80 cents per therm and gasoline wholesales for about $2.25 per gallon, so natural gas is a bargain in cents per BTU.


last line should read:
1 us gallon gasoline equivalent 100ft3 NG


CH4 is the cleanest carbone based fuel as well as the most efficient (high octane, more H than C) it is abundant as a fossil energy and can be renewably made from biomass with high EROI, but :

The improvment of the storage onboard is only part of the problem, the transportation of NG over long distances is still the most difficult part of the problem and cost 10 times more than the transportation of liquid fuel.

Also one thing they never mentionne is the percentage in weight that their Material can store. Let says you need ~ 30Kg of CH4 for 400 miles autonmy,if they can absorb 10% in weight (which is quite good) you are in the 300Kg (600pounds) that's a lot... we have seen quite some announcement about these materail that can store CH4 at low pressure but the never give this information, the importance of which is more than the ratio of volume.

Healthy Breeze

Another thing I wonder about is how much of that adsorbed CNG you can easily draw out when you want? I'm guessing that if CNG likes adsorbing onto this high surface area material, that it doesn't want to let go too easily. Also, how is affected by temperature? I left me cell phone (off) in a frozen car overnight on a ski trip and in the morning, the charge indicator said the battery was dead even though it had a full charge. I left it on the heat vent for 2 minutes and suddenly it said it had a full charge again. Anyway, I'm guessing this process is sensitive to the usual -20 to +40 degrees celsius range most cars have to deal with.

More than half the homes in the U.S. are heated with natural gas, but only use 20% of the natural gas consumed. Your house uses more natural gas year around than your HEV would driving 20k miles per year.
IIRC, the typical gas-heated home uses about 50 million BTU/year.  That's equivalent to 400-odd gallons of gasoline, which is very substantial; you'd need to average ~50 MPG over 20,000 miles to keep vehicular consumption down to that.

Given NA natural gas's constrained supply and inelastic demand, asking another 10% for vehicle fuel would increase the price A LOT.  It would essentially price some consumers (including residential users) out of the market.  It is much like converting corn to gasoline-helper at the expense of people who like to eat.

It would make far more sense to burn the gas in something like Climate Energy cogenerating furnaces.  This yields both heat and electricity; the heat for space heat, the electricity to charge your PHEV.  Supplement the cogenerator with electric heat from wind when it's blowing, and you could see natural gas consumption go down.

Rafael Seidl

@ Brian P -

the paper gives a gravimetric density of 0.871 g/cm^3 for PCN-14, roughly the same as diesel fuel. The upshot is that the tank walls will be much thinner than in a CNG system yet total weight will be the same or more. That's why it would be useful to shape ANG tanks such that they can do double duty as soundproofing.

@ sjc -

CNG = natural gas at 200-300 atmospheres

ANG = adsorbed natural gas at ~35 atmospheres, i.e. backbone pipeline pressure. Filling stations connected directly to the backbone would not need to invest in compressors at all, nor would any additional (electrical) energy be required for the filling process.

There is no such thing as adsorbed CNG.

Mike Z.

I've seen CNG buses and trucks as well, my question is can Nat Gas be used in the Diesel cycle or does these buses use an OTTO cycle engine?


NG engines are spark-ignition.


In Argentina most of CNG vehicles are spark ignition , gasoline engines modified to CNG (dual mode) and diesel engines modified to CNG (Otto cycle, quit the injectors ,put spark plugs, modified pistons, etc).
But there are some trucks modified to work with diesel and CNG at the some time in a variable percentage depending on the load. There´s an article in GCC of some time ago about such a system.

Rafael Seidl

@ Mike Z -

the thermodynamic cycle for natural gas is the Otto cycle. A spark plug or other external trigger (e.g. diesel pilot injection, laser ignition) is required to initiate combustion. Except for very large engines, iridium-tipped points are typically used.

However, since most NG engines today are very large stationary gensets or bus engines, they are usually derived from diesel engine designs. Natural gas has a research octane number of 120-130 (depending on impurities), permitting geometric compression ratios as high as ~14. That is less than is possible in a diesel engine but higher than for gasoline designs. The extra mechanical strength afforded by a beefy crankcase, cranktrain and cylinder head is therefore no luxury.

For mobile applications, the distribution networks for NG fuel are still patchy. Passenger car NG engines are therefore almost always derived from gasoline engines and adapted for bivalent operation. In a pinch, they must run on gasoline stored in a small emergency tank. This emergency facility limits the feasible geometric compression ratio of mobile CNG engines to ~12 to avoid engine knock. Even that number is only possible with direct injection and severe retardation of the ignition timing when running on the inferior fuel. The result is poor fuel economy and reduced power in this emergency mode.


ANG is the term, but the point is NG is a good transportation fuel. I know people in colder climates that use a LOT more than 500 therms per year.

ANG in a hybrid could get you 40 mpg. The point is, the more ANG, CNG and dual fueled cars on the road replacing gasoline cars, the less imported oil.

Since NG is a good value compared to gasoline, there would be quite a savings for the individual. It is cleaner and available in the garages of 70% of the homes, so I do not think that there is a problem transporting NG to the consumer. If I were a fueling station owner, it seems like it would be easier for me to install CNG than hydrogen.

I think it is more beneficial to discuss the merits of the concepts and not get bogged down in three letter acronyms and whether you have calculated to the third decimal point. In a Green Car Congress, I would hope that we would discuss the merits of an idea and not try to be the smartest person in the room.

By the way, in my reading of adsorbed NG they say that you could go higher in pressure and store even more. It did not sound to me like adsorbed NG stops at 500 psi.


@EP: It makes more sense when adequate electric storage is available and biogas is blended with other methane and used to power gas turbines.

Unfortunately, warnings from you and others about peak natural gas go mostly unheeded. The only place where some shift may be occuring is CAFOs (Confined Animal Feed Operations). Perhaps, we shall see more investment in such anaerobic digestion as NG prices rise further.

Mike Z.

I've started to develop an intrest in natural gas. The first thing that is obvious in looking at Natural gas is that production clearly does not follow a hubbert distribution. In fact it follows more of a linear depletion pattern. So the term 'Peak natural gas' is really a moot point.

Roger Pham

ANG (Adsorbed Nat. GAs) is one viable solution for petroleum dependency, just like PHEV's, but less expensive due to the fact that an ANG tank would be a lot less expensive than a 10-16 kwh battery, and more durable. Methane is a renewable fuel from various sources like cellulosic biomass, synthesized from renewable H2 or nuclear H2, and from coal also.

NG can be used in diesel engine using the diesel cycle at high compression by using a pilot injection of diesel fuel to ignite the NG. In this way, there is no efficiency penalty at part load for using NG. At full load, efficiencies of Otto cycle and Diesel using NG are comparable.

To avoid the problem of lack of availability of NG at the gas station, the government should mandate all larger gas stations to make NG available to motorists, AND mandating that more and more cars (HEV's) should run on methane exclusively, in order to avoid the efficiency tradeoff and weight and cost of bi-fuel vehicle (gasoline and methane). This is similar to the CARB's ZEV mandate, but much easier to carry out. ANG would make this less expensive since no compression would be required for the gas station.


It is my understanding that natural gas production peaked in the U.S. early 1970s. Recently, there has been more exploration and development, but without a price floor the risk of price fluctuations has not helped.

Since we can make methane from biomass, perhaps the price needs to rise from 80 cents per therm wholesale closer to $1 per therm and a price floor set. This might bring on more development of fossil and biomass sources.

15% of our natural gas in the U.S. comes from Canada. Canada may be reducing their exports of natural gas to the U.S. over time, so now may be the time to take some action.

Solar thermal heating of homes has been shown effective.

While this was district heating, the same principles might apply to individual homes as well.

We might save enough natural gas with solar thermal heating to run our car. Since a lot of natural gas is used to run peaking plants to provide electricity for AC, absorption cooling using solar thermal could help there as well.


While I think ANG would make for a much cleaner fuel for a range extender than gasoline. I would be concerned about a wholesale conversion to NG for transportation for the following reasons.

1) NG is still primarily a fossil fuel
1a) Limited global supplies (post peak in NA)
1b) Although much cleaner than gasoline it still creates tailpipe pollution.
1c) Carbon positive

2) I'm not entirely comfortable putting our transportation energy in direct competition with our primary source of home heating. (much like ethanol competes with our food supply). Do we really want all of our eggs in one basket?

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