Synthesis of polycarbonate diol catalyzed by metal-organic framework Zn_4O[CO_2-C_6H_4-CO_2]_3

The metal-organic framework Zn4O[1,4-benzenedicarboxylate]3(Zn4O[CO2-C6H4-CO2]3,commonly known as MOF-5,was prepared by the ultrasonic irradiation method.The catalyst was characterized by X-ray diffraction(XRD) and Fourier transform infrared(FTIR) spectroscopy.It was then used as the catalyst for the preparation of polycarbonate diol(PCDL) via the transesterification between diphenyl carbonate(DPC) and 1,6-hexandiol(1,6-HD).Its catalytic activity in the transesterification process is evaluated by the yield of phenol,and its catalytic activity in the polycondensation process is determined by the number-average molecular weight(Mn) and the hydroxyl value.Compared to the triethylenediamine(C6H12N2),Mg-Al layered double hydroxide(Mg-Al LDH),sodium ethoxide(C2H5ONa) and sodium methoxide(CH3ONa),MOF-5 exhibits highest catalytic activity for the preparation of PCDL.Under reaction conditions(n(1,6-HD)/n(DPC) = 1.2,w(catalyst) = 0.03%,198 ℃),the yield of phenol is up to 90.1% and the PCDL shows highest Mn and lowest hydroxyl value.

Synthesis of Polycarbonate Diols（PCDLs） via Two-step Process Using CH3COONa as an Effective Catalyst

Polycarbonate diols（PCDLs） with a number average molecular weight（M,） of 2800 and a narrow polydispersity index（PDI=1.33） were synthesized from dimethyl carbonate（DMC） and 1,4-butarlediol（BD） via a two-step process. The influences of the molar ratios of DMC to BD in the feedstock, polycondensation temperature and polycondensation time on the PCDLs preparation were studied. CH3COONa showed the best catalytic performance among the catalysts studied. The highest BD conversion of 73.8% and PCDLs yield of 64.7% were achieved under its optimum reaction conditions. Furthennore, based on the results of 1^H NMR, the relationships between the ratio of end groups （--OCH3/-OH） of oligomers, the Mn and chain-end constitute of resultant polycarbonates were also investigated. The results indicate that PCDLs can be synthesized when the oligomers mostly bear hydroxyl end groups. In contrast, it was impossible to prepare PCDLs when the oligomers were enriched with methyl carbonate end groups,