@article{64019,
  abstract     = {{A chiral zirconium-based catalyst, DUT-67-Pro containing 8-connected Zr6-clusters is obtained by post synthetic functionalization of Zr6O6(OH)2(TDC)4(HCOO)2 (DUT-67, TDC = 2,5-thiophenedicarboxylate) with the chiral monocarboxylic acid, L-proline. 13C and 15N solid state MAS and DNP NMR studies of DUT-67-Pro confirm the integration of L-proline into the porous framework. The chiral MOF catalyst exhibits an excellent catalytic activity at low temperature (298 K) with an unprecedented syn-(S,S)-product selectivity in an asymmetric aldol addition reaction of cyclohexanone to 4-nitrobenzaldehyde (yield = 95%, ee = 96%). Comparative catalytic studies using a molecular Zr6-cluster model compound indicate the Zr6-moiety to be responsible for this inverse diastereoselectivity compared to well-established L-proline organocatalysis and a mechanism is proposed to explain the Zr6-cluster-mediated syn-selectivity. Masking residual acidic active sites in the cluster of the framework was found to be a key prerequisite to achieve the high enantioselectivity. The purely heterogeneous catalytic system based on DUT-67-Pro is highly stable and can be recycled several times.}},
  author       = {{Nguyen, Khoa D. and Kutzscher, Christel and Ehrling, Sebastian and Senkovska, Irena and Bon, Volodymyr and Oliveira, Marcos and Gutmann, Torsten and Buntkowsky, Gerd and Kaskel, Stefan}},
  journal      = {{Journal of Catalysis}},
  keywords     = {{-proline, -selective aldol reaction, Chirality, Metal-organic framework, Zirconium}},
  pages        = {{41–50}},
  title        = {{{Insights into the role of zirconium in proline functionalized metal-organic frameworks attaining high enantio- and diastereoselectivity}}},
  doi          = {{10.1016/j.jcat.2019.07.003}},
  volume       = {{377}},
  year         = {{2019}},
}