Functionalising carbon-hydrogen bonds in methane is a particularly challenging process that most known catalysts can achieve only under extremely acidic and/or oxidising conditions. However, microscopic crystalline structures called metal-organic frameworks (MOFs) may provide a way to solve one of the biggest problems in methane functionalisation catalysis, an economically important chemical process.
Researchers have been constantly looking to transform methane into something more valuable. One such product could be methanol.
A team led by Delferro and Omar Farha, associate professors of chemistry at Northwestern University, has demonstrated a new way to activate methane with MOFs, as a result of their joint efforts in the Inorganometallic Catalyst Design Center. They and seven co-authors recently published their method in Nature Catalysis.
According to the team, MOFs can selectively pro- duce a specific boron-infused methane product by shape-selective catalysis, a widely used industrial technique for chemical synthesis and hydrocarbon processing. Shape-selective catalysis can distinguish between molecules that are slightly different in size and may selectively form only one desired chemical product. But, for the technique to work, the pore space of the catalyst must be comparable to the size of the molecules involved in the reaction.
In MOFs, organic molecules and metal oxide clusters serve as the links and nodes, respectively. MOFs are attractive candidates for performing shape-selective catalysis because they are structurally tunable, according to lead author Xuan Zhang of Northwestern and his colleagues.
In the next phase of their research, Delferro and Farha will attempt to activate methane with the same chemistry, but they will substitute earth-abundant metals such as iron, cobalt, nickel and copper for iridium, which is rare and expensive.