Structures and mechanisms of the carbonyl-ene reaction between MOF-11 encapsulated formaldehyde and propylene: An ONIOM study

Metal-organic framework structures containing formaldehyde (HCHO@MOF-11) and its interactions with propylene were investigated by density-functional (B3LYP/6-31G(d,p)) and ONIOM (B3LYP/6-31G(d,p): UFF) calculations. For comparison, the carbonyl-ene reaction of propylene and formaldehyde was also studied with Cu+ alone as a catalyst. It was found that the metal-organic framework leads to an energy barrier of the reaction Delta E-act of 24.1 kcal/mol. This compares to values of Delta E-act of 34.4 kcal/mol for the uncatalyzed system and 6.4 kcal/mol if the reaction takes place with the Cu+ alone. The carbonyl-ene reaction of propylene using HCHO @ MOF-11 takes place in a single concerted reaction step. The Delta E-act value for MOF-11 is similar to that obtained for the zeolite catalyzed reaction (Delta E-act = 25.1 kcal/mol, HCHO@Na-faujasite/CH3CH=CH2).