What some microorganisms have been able to do seemingly effortlessly for billions of years, humans can only do with great effort: Mankind invests more than one percent of global energy production in the synthesis of nitrogen compounds.

The starting material is atmospheric nitrogen, which is plentiful.

Around 78 percent of the earth's atmosphere consists of this gas.

The product of the so-called nitrogen fixation is usually ammonia (NH3).

In particular, artificial fertilizer is produced from this, without which there would be no agriculture that can feed eight billion people.

Fritz Haber and Carl Bosch, who later won the Nobel Prize, succeeded in fixing the first technical nitrogen in 1913. Since then, ammonia has been produced from hydrogen (H2) and nitrogen using the Haber-Bosch process.

In order for the reaction to take place, however, in addition to suitable catalysts, high temperatures and pressures of around 500 °C and 200 bar are required - and therefore a great deal of energy.

Atmospheric nitrogen is present as "N2", i.e. molecules made up of two nitrogen atoms each.

For the formation of other nitrogen compounds, the bond between the two atoms in the N2 molecule must be broken.

However, this is one of the strongest chemical bonds of all.

The microorganisms mentioned at the beginning now have evolutionarily optimized bio-catalysts, so-called nitrogenases,

to fix the nitrogen in the air and thus make it usable for all other organisms in the food chain.

Shouldn't human chemistry also be able to procure its nitrogen compounds more efficiently?

One way of making industrial nitrogen fixation more energy-efficient would be to facilitate the separation of the ammonia from the Haber-Bosch reactor.

Until now, it had to be liquefied with cooling and then distilled.

Heating and cooling uses significant amounts of energy.

The new development by a Californian research group led by Jeffrey R. Long could help here: The scientists present a new material in the journal "Nature" that efficiently binds ammonia, stores it and releases it again when needed.

It is a so-called MOF (for

metal organic framework

), a metal–organic framework through which gases can move freely.

Copper atoms, which like to bind ammonia molecules and incorporate them into the surrounding framework structures, are located at certain points in the MOF.

Other gases, on the other hand, flow out of the pores undisturbed.

The ammonia can later be flushed out again by applying a vacuum and heating, thereby regenerating the storage material.

As the researchers report, their MOF could be used to remove the ammonia directly from the manufacturing process - without distillation, without liquefaction and therefore without cooling.