Functionalization of CPO-27-Ni through metal hexacarbonyls: The role of open Ni ²⁺ sites

Cr(CO) ₆ and Mo(CO) ₆ have been used as precursors to obtain grafted (η ⁶-arene) M(CO) ₃ species inside the CPO-27-Ni material. The presence of open Ni(II) sites in the MOF scaffold promotes distinctive reactivities with respect to that observed previously on other MOFs (MOF-5 and UiO-66). The formation of two organometallic M(CO) ₃(η ⁶-arene) conformers (staggered and eclipsed) has been considered, also taking into account data obtained by a recent theoretical work. IR spectroscopy shows how open metal sites in a MOF structure can destabilize metal carbonyl molecules, favoring CO elimination and acting as CO scavenger, which fastens the decomposition and frustrate the reverse reaction. The work can open new studies on precursors of catalytic species stabilized inside MOFs cages.