35652-55-2Relevant academic research and scientific papers
A lanthanide MOF catalyst with an excellent thermal stability for the synthesis of polycarbonate diol
Wang, Liping,He, Jiao,Chen, Xueying,Lv, Yanling
, p. 2335 - 2343 (2020)
A lanthanide metal–organic framework (MOF) Yb(BTC)(H2O)·(DMF) (BTC = 1,3,5-benzenetricarboxylate, DMF = N,N-dimethylformamide) was prepared from Yb(NO3)3·5H2O and H3BTC using the solvothermal method and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, N2 adsorption–desorption technology, and temperature-programmed desorption. The results show that Yb(BTC)(H2O)·(DMF) is a lanthanide MOF with an excellent thermal stability. The coordinated water molecules and DMF guest molecules were removed from the channels by calcination to form a porous solid Yb (BTC) with coordinatively unsaturated Yb3+ sites. The BET surface area and pore size of Yb(BTC) are 695?m2/g and 0.68?nm, respectively. As a heterogeneous Lewis acid catalyst, the activity of Yb(BTC) for the synthesis of polycarbonate diol (PCDL) via transesterification between diphenyl carbonate and diol was investigated. Compared with nine reported catalysts, Yb(BTC) exhibits the highest catalytic activity for the synthesis of PCDL.
Intramolecular acceleration of asymmetric epoxide ring-opening by dendritic polyglycerol salen-CrIII complexes
Keilitz, Juliane,Haag, Rainer
supporting information; experimental part, p. 3272 - 3278 (2009/12/24)
We present the synthesis of symmetrical (pyrrolidine-salen)CrIII complexes immobilized on hyperbranched polyglycerol 1 through linkers of different lengths and their application in the asymmetric ring-opening of meso-epoxides. This reaction proceeded through a cooperative bimetallic mechanism and for the polymeric catalysts a positive dendritic effect with regard to the reaction rate was found. In addition, the introduction of long linkers (C6, Cl0, and C18) forced the favored head-to-tail orientation of two catalyst molecules and led to greater enantioselectivity with ee values of 48% (cyclohexene oxide) and 64 % (cyclopentene oxide) for the ring-opening of meso-epoxides with TMSN3 catalyzed by hPG-C10CrCl (13). The soluble polyglycerol-supported catalyst was recovered five times by dialysis to afford similar activities and a 10% increase in the enantioselectivity.
