Molecular rhodium complex within N-rich porous polymer macroligand as heterogeneous catalyst for the visible-light driven CO2 photoreduction

The heterogenization of molecular catalysts within a porous solid acting as macroligand can advantageously open access to enhanced stability and productivity, and thus to more sustainable catalytic process. We report here porous organic polymer (POP) made through metal-free polymerization using bipyridine repeating units. This N-rich POP is an efficient macroligand for the heterogenization of molecular rhodium complexes. The intrinsic catalytic activity of the heterogenized catalyst is slightly higher than that of its homogeneous molecular counterpart for formic acid production as unique carbon containing product. The heterogenization of the rhodium catalysts enables recycling for a total productivity up to 8.3 grams of formic acid per gram of catalyst after 7 cycles of reaction using visible light as sole energy source

Heterogenized Molecular Rhodium Phosphine Catalyst within Metal-Organic Framework for Ethylene Hydroformylation

Molecularly-defined organometallic rhodium phosphine complexes were efficiently heterogenized within a MOF structure without affecting neither their molecular nature nor their catalytic behavior. Phosphine-functionalized MOF-808 served as solid ligand in a series of eight rhodium phosphine catalysts. These MOF-heterogenized molecular catalysts showed activity up to 2100 h-1 for ethylene hydroformylation towards pro-pionaldehyde as sole carbon-containing product. Combined experimental and computational methods applied to this unique MOF-based molecular system allowed unravelling structure and evolution of the Rh active species within the MOF under catalytic conditions, in line with molecular mechanisms at play during the hydroformylation reaction. The MOF-808 designed as a porous crystalline macroligand for well-defined molecular catalysts allows benefiting from molecular-scale understanding of interactions and mechanisms as well as from stabilization through site-isolation and recycling ability

Stage-dependent effects of epidermal growth factor on Ca2+ efflux in mouse oocytes

Epidermal growth factor (EGF) has received much attention recently for its positive effects on mammalian oocyte maturation and embryo development and its potential importance in cytoplasmic maturation of oocytes. Calcium (Ca2+) homeostasis in germinal vesicle stage oocytes has also been suggested to play a role in cytoplasmic maturation. This study examined the effects of EGF on Ca2+ mobilization as measured by its efflux from mouse oocytes at three time periods throughout maturation (0–4 hr, 4–8 hr, and 12 hr). Immature cumulus oocyte complexes (COCs) removed from the ovary for less than 4 hr exhibit oscillations in Ca2+ efflux that initiated 5–30 min following EGF stimulation. This response was not observed in COCs matured for 4–8 hr or 12 hr or in unstimulated 0–4 hr COCs. Denuded oocytes and cumulus cells did not show the same response to EGF (8.2 nM and 16.4 nM). Immunohistochemistry for detection of the EGF receptor along with EGF internalization studies showed that receptors are present both on cumulus cells and the oocyte but EGF appears to be internalized mainly by the cumulus cells. These data demonstrate that EGF induces oscillations in Ca2+ efflux in COCs 0–4 hr old and this response is mediated by the cumulus cells. Mol. Reprod. Dev. 53:244–253, 1999