Metal–organic
frameworks (MOFs) with flexible gas-adsorbing pores could make
the driving range
of adsorbed-natural-gas (ANG) cars comparable to that of
a typical
gasoline-powered car.
(October 27, 2015) Berkeley
Lab Researchers Find a Better Way to Store Natural Gas as a Transportation Fuel
With new makes of all-electric and hybrid automobiles
seeming to emerge as fast as the colors of fall, it is easy to overlook another
alternative to gasoline engines that could prove to be a major player in
reduced-carbon transportation – cars powered by natural gas. Natural gas, which
consists primarily of methane (CH4) is an abundant, cheaper and cleaner burning
fuel than gasoline, but its low energy density at ambient temperature and
pressure has posed a severe challenge for on-board fuel storage in cars. Help
may be on the way.
Researchers with the U.S. Department of Energy (DOE)’s
Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a variety
of metal–organic frameworks (MOFs) – sponge-like 3D crystals with an
extraordinarily large internal surface area – that feature flexible
gas-adsorbing pores. This flexibility gives these MOFs a high capacity for
storing methane, which in turn has the potential to help make the driving range
of an adsorbed-natural-gas (ANG) car comparable to that of a typical
gasoline-powered car.
Space-filling
models of cobalt-bdp MOF in the collapsed state (left) and CH4-expanded
state (right). The
purple, gray, blue, and white spheres represent Co, C, N,
and H atoms,
respectively.
“Our flexible MOFs can be used to boost the usable capacity
of natural gas in a tank, reduce the heating effects associated with filling an
ANG tank, and reduce the cooling effects upon discharging the gas from the ANG
tank,” says Jeffrey Long, a chemist with Berkeley Lab’s Materials Sciences
Division and the University of California (UC) Berkeley who is leading this
research. “This ability to maximize the deliverable capacity of natural gas
while also providing internal heat management during adsorption and desorption
demonstrates a new concept in the storage of natural gas that provides a
possible path forward for ANG applications where none was envisioned before.”
The cobalt-bdp MOF
features flexible square-shaped pores
that expand under
pressure to adsorb increasing amounts of methane gas.
Long is the corresponding author of a Nature paper that
describes this work entitled, “Methane storage in flexible metal–organic
frameworks with intrinsic thermal management.” The lead author is Jarad Mason,
a member of Long’s research group at the time of this study and now at
Northwestern University. (See below for
a complete list of co-authors.)