Direct conversion of methane to methanol with zeolites: towards understanding the role of extra-framework d-block metal and zeolite framework type.

The direct conversion of methane to methanol has been an active area of research for over a century, though a viable industrial process is yet to be realised. However, in the last three decades substantial progress has been made in the field through homogeneous and heterogeneous approaches. This perspective article explores the latest advances in the field of direct methane to methanol conversion by zeolites containing extra-framework d-block metals, focussing on first row, d-block metals. The article highlights the similarities and differences in the nature and formation of the active site, the mechanism of methane activation as well as mode of functionalisation, and where appropriate draws on understanding gained from theoretical studies. From the insight obtained into the different roles of the extra-framework metal and zeolite framework we propose new areas of research which the authors believe will be of benefit to the field.