Chemistry in confined spaces: Reactivity of the Zn-MOF-74 channels

摘要

Using infrared spectroscopy combined with ab initio methods we studyreactions of H$_2$O and CO inside the confined spaces of Zn-MOF-74 channels.Our results show that, once the water dissociation reactionH$_2$O$\;\rightarrow\;$OH+H takes place at the metal centers, the addition of40 Torr of CO at 200 $^{\circ}$C starts the production of formic acid viaOH+H+CO$\;\rightarrow\;$HCO$_2$H. Our detailed analysis shows that the overallreaction H$_2$O+CO$\;\rightarrow\;$HCO$_2$H takes place in the confinement ofMOF-74 without an external catalyst, unlike the same reaction on flat surfaces.This discovery has several important consequences: It opens the door to a newset of catalytic reactions inside the channels of the MOF-74 system, itsuggests that a recovery of the MOF's adsorption capacity is possible after ithas been exposed to water (which in turn stabilizes its crystal structure), andit produces the important industrial feedstock formic acid.