Compartmentalization of catalysts into metal-organic polyhedra gel for cascade reactions

2021 Fiscal Year Research-status Report

• Project/Area Number: 20K15366
• Research Institution: Kyoto University
• Principal Investigator: LEGRAND ALEX 京都大学, 高等研究院, 特定研究員 (00836372)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: metal-organic polyhedra / self-assembly / soft matter / catalysis / metal nanoparticle

Outline of Annual Research Achievements

Silver nanoparticles have been synthesized within metal-organic polyhedra (MOPs), a new class of hybrid organic-inorganic molecular cage build from the coordination between dirhodium paddlewheel metal precursors and dicarboxylic organic ligands. The cage serves here as host material for the accomodation of guest metal nanopraticles (MNPs). Through this strategy MNPs of few nm can be confined and stabilized within the cavity of the MOP. In addition, the MOP presents the advantage of having labile axial metal sites, provinding the possibility to extand the assembly of the cage in the 3D of space in order to form hierarchical structures such as colloidal gel network or colloidal particles. With this strategy, and by taking advantage of the confined MNPs and metal nodes as catalytic active species more complex systems might be obtain for orthogonal catalysis application for example.

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

So far, the main was the synthesis and characterization of Au(0) metal naoparticles within cuboctahedral MOP. The cage posses a pore of ~ 2nm and the resulting MNPs of Au should possess a similar size. After synthesis in solution, the cage remain soluble and no sedimentation is observe other the course of several month. In addition, DLS analysis of AU@MOP demonstrate a size (~ 3 nm) close to the one of the cage. The difference is explained by the hydrodynamic radius that take into account a solvent shell around the cage. Direct evidence of the presence of confined MNPs within the cage is challenging as HR-TEM observation require to evaporate the solvent which lead to aggregation formation and thus render difficult the determination of the size.

With this potential MNPs@MOP, addition of ditopic N-donor linker was performed in order to obtain the kinetically trapped phase of the hybrid system via the simultaneous coordination of all metal axial site. This strategy previously reported by our group is a prerequisite for the formation of the colloidal gel network. However, even if the kinetically trapped phase has been obtain as demonstrated by UV-vis spectroscopy, no gel was obtain upon heating.

Strategy for Future Research Activity

For the futur work, different cages with different geometry or using organic ligand possessing functional group decorating the internal surface of the cage will be synthesized. This should profide adequate environment for the stabilization of the MNPs within the cage.
For the assembly of the cage into hierarchical structures, colloidal particles will be synthesized insted of colloidal gel. Stepwise addition of N-donor ditopic linker will allow the formation of colloidal particles of controlled sized.

Causes of Carryover

Due to COVID situation, I could not attend to conferences that was initially planned in the budget. In addition, the more challenging chracterization of the MNPs@MOP systems prevented so far any resutls to be published. So money for publication cost was not spent.