Aiguo Hu

Nanoscale Metal–Organic Frameworks for Ratiometric Oxygen Sensing in Live Cells

We report the design of a phosphorescence/fluorescence dual-emissive nanoscale metal-organic framework (NMOF), R-UiO, as an intracellular oxygen (O2) sensor. R-UiO contains a Pt(II)-porphyrin ligand as an O2-sensitive probe and a Rhodamine-B isothiocyanate ligand as an O2-insensitive reference probe. It exhibits good crystallinity, high stability, and excellent ratiometric luminescence response to O2 partial pressure. In vitro experiments confirmed the applicability of R-UiO as an intracellular O2 biosensor. This work is the first report of a NMOF-based intracellular oxygen sensor and should inspire the design of ratiometric NMOF sensors for other important analytes in biological systems.

Highly enantioselective catalytic asymmetric hydrogenation of β-keto esters in room temperature ionic liquids

Polar phosphonic acid-derived Ru-BINAP systems were used to catalyze asymmetric hydrogenation of beta-keto esters in room temperature ionic liquids (RTILs) with complete conversions and ee values higher than those obtained from homogeneous reactions in MeOH (up to 99.3%), and were recycled by simple extraction and used for four times without the loss of activity and enantioselectivity.

Immobilization of chiral catalysts on magnetite nanoparticles for highly enantioselective asymmetric hydrogenation of aromatic ketones

Magnetite nanoparticle (MNP)-supported asymmetric catalysts were synthesized by direct immobilization of a 4,4′-bisphosphonic acid-substituted BINAP-Ru-DPEN complex onto MNPs. The resulting heterogeneous catalyst (7) was highly active for the asymmetric hydrogenation of a wide range of aromatic ketones with remarkably high activity (>99% conversion with 0.1 mol% catalyst) and enantioselectivity (up to 98.1% ee) as a result of the bulky 4,4′-substituents (i.e., phosphonic acid groups) on BINAP. Catalyst 7 could be readily recycled and reused through simple magnetic decantation 9 times without the loss of activity or enantioselectivity. An alternative strategy was also explored to immobilize the [4,4′-(TMS)2-BINAP]-Ru-DPEN complex onto MNPs by first grafting a DPEN derivative onto the MNP surface followed by complexation of [4,4′-(TMS)2-BINAP]-Ru(DMF)2Cl2 to the surface-bound DPEN, but this immobilization strategy did not provide a robust heterogeneous catalyst, presumably due to oxidation of the Ru(II) intermediate by iron oxide nanoparticles.

Successful Coupling of a Bis-Amidoxime Uranophile with a Hydrophilic Backbone for Selective Uranium Sequestration

The amidoxime group (-RNH2NOH) has long been used to extract uranium from seawater on account of its high affinity toward uranium. The development of tunable sorbent materials for uranium sequestration remains a research priority as well as a significant challenge. Herein, we report the design, synthesis, and uranium sorption properties of bis-amidoxime-functionalized polymeric materials (BAP 1-3). Bifunctional amidoxime monomers were copolymerized with an acrylamide cross-linker to obtain bis-amidoxime incorporation as high as 2 mmol g-1 after five synthetic steps. The resulting sorbents were able to uptake nearly 600 mg of uranium per gram of polymer after 37 days of contact with a seawater simulant containing 8 ppm uranium. Moreover, the polymeric materials exhibited low vanadium uptake with a maximum capacity of 128 mg of vanadium per gram of polymer. This computationally predicted and experimentally realized selectivity of uranium over vanadium, nearly 5 to 1 w/w, is one of the highest reported to date and represents an advancement in the rational design of sorbent materials with high uptake capacity and selectivity.