Bridging the gap between homogeneous and heterogeneous catalysis through MOF supported catalysts
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abstract
Heterogenizing molecular homogeneous catalysts while conserving their catalytic activity is one of the outstanding challenges of surface chemistry.1-3 Current widely-employed catalyst supports such as inorganic oxides suffer from the loss of catalytic activity of the tethered species because of the mutually deactivating interactions between the active sites that stems from poorly defined surfaces of oxide supports. On the other hand, Metal-Organic Framework (MOF) materials have distinct advantages for application as catalyst solid supports over these inorganic oxides due to their well-defined crystalline structure and porosity. Because of these advantages, MOFs have, a yet to be fully tapped, capability to be employed as solid state support platforms for heterogenizing homogeneous catalysts that would allow for conservation or even amplification of the catalytic activity of tethered moieties. Herein, we propose application of MOF based solid state support materials to address some of the challenges of heterogenizing homogeneous molecular catalysts with conservation or amplification of catalytic activity of parent homogeneous moieties. In this project, MOFs with high thermal, chemical and mechanical stability will be functionalized with mono- and bidentate nitrogen and phosphorus ligands through a series of well-precedented methods of postsynthetic modification of MOFs. These ligand functionalized MOFs will then be metallated with a variety of transition metals including Cr, Ni, Ag, Rh, Pd, Ir and Pt to access functionalized MOF materials tethered with a wide-range of well-known transition metal based molecular catalysts. The prepared functionalized materials will be tested in reactions of a wide range of complexity ranging from simple hydrogenations and olefin oligomerizations to catalytically more challenging carbon-carbon and carbon heteroatom couplings and hydroamination reactions. The prepared MOF materials with tethered catalytic moieties are anticipated to have one or more of the following advantages over their parent homogeneous analogs: a â because of the immobilization of the molecular catalysts on the MOF surface, conservation or even improvement of catalytic activity due to limiting the mutually deactivating interactions between the catalytically active species; b â Ability to operate in solvents that cannot dissolve the parent homogeneous catalyst and in gas-phase c â Ability to recycle the catalyst.
