  Metal organic frameworks are nano porous adsorbents of relevance to gas
separation and catalysis, and O2 separation from air is essential to diverse
industrial applications. A metal organic framework Fe2(DOBDC), also known as a
MOF74, can selectively adsorb O2 in a manner that defies the classical picture:
Adsorption sites either do or do not share electrons over a long range. This
report proposes, and then justifies phenomenologically and computationally, a
mechanism. Charge transfer mediated adsorption of an electron acceptor O2 in a
quasi one dimensional (1D) electron donor semiconductor Fe2(DOBDC) drives and
is driven by 1D metal insulator transitions that localize or delocalize the 1D
electrons. This mechanism agrees with the empirical evidence, and predicts a
class of nano porous semiconductors or metals and potential adsorbents and
catalysts in which chemistry and metal insulator transitions intertwine.
