[Co_(3)]簇基金属有机框架材料实现“一石二鸟”高效催化CO_(2)转化为噁唑烷酮

[Co_(3)]-Cluster Based Metal-Organic Framework Enables“Two Birds with One Stone”in Efficient Transformation of CO_(2) to Oxazolidinones

噁唑烷酮是药物化学中重要的中间体,可以通过炔丙基胺类或氮杂环类化合物与CO_(2)的环化获得。合成一种可以同时催化这两种反应的催化剂是一件有很强吸引力,但极具挑战性的工作。本文合成了一例独特的三维(3D)[CO_(3)]簇金属-有机框架(MOF){(CH_(3)NH_(2)CH_(3))2[CO_(3)(BCP)_(2)]·6H_(2)O·4DMF}n(1)并进行了表征,1表现出良好的溶剂稳定性和热稳定性。催化实验结果表明,1可以高效催化氮杂环或炔丙基胺类化合物与CO_(2)反应来制备噁唑烷酮,并且催化剂对两种反应都具有广泛的底物普适性和良好的循环使用性。对照实验和核磁共振测试表明,1中路易斯酸和路易斯碱位点的共存是高效催化的原因。化合物1作为一种新型催化剂,成功实现了“一石二鸟”高效催化CO_(2)转化为噁唑烷酮。

CO_(2),as a greenhouse gas,has excessive emissions that lead to many environmental problems and is a rich and cheap C1 resource.Effective utilization and transformation of CO_(2) has become an important means of achieving carbon neutrality.Oxazolidinones are important intermediates in pharmaceutical chemistry that can be synthesized by carboxylation cyclization of CO_(2) with propargyl amines or cycloaddition of CO_(2) with aziridines.Owing to CO_(2)’s high stability,these reactions typically require harsh conditions,such as high temperatures or pressures.It is desirable,but challenging,to find a catalyst that can catalyze these two types of reactions under relatively mild conditions.Metal-organic frameworks(MOFs)are an emerging class of heterogeneous catalysts that with great potential in the catalytic conversion of CO_(2) to value-added products because of their attractive features,such as abundant metal active sites,inherent porosity,and easy functionalities.Herein,a unique three-dimensional(3D)MOF,{(CH_(3)NH_(2)CH_(3))_(2)[Co_(3)(BCP)_(2)]·6H_(2)O·4DMF}n(1)(H_(4)BCP:5‐(2,6‐bis(4‐carboxyphenyl)pyridin‐4‐yl)isophthalic acid;DMF:N,N'‐dimethylformamide),was synthesized using carboxylic acid ligands and cobalt salts via a solvothermal method.According to structural analysis,[Co_(3)]clusters as secondary building units(SBU)are bridged by BCP4−ligands,forming an anion framework with flu topology,and dimethylamine cations act as counter ions in the pores.The framework has rectangular channels of approximately 0.4 nm×0.9 nm along the a-axis direction,exhibiting its porous property.Infrared spectroscopy(IR)and X-ray photoelectron spectroscopy(XPS)characterizations proved the coordination interaction between the carboxyl groups in the ligands and the metal ions.The powder X-Ray diffraction(PXRD)test further confirmed the phase purity of the synthesized samples.PXRD and thermogravimetry(TG)analyses indicated that 1 possessed good solvent and thermal stabilities.The catalytic experiments revealed that 1 could effectively catalyze CO_(2) with aziridines or propargyl amines to prepare oxazolidinones.In the cycloaddition of CO_(2) with aziridines,1 can facilitate the reaction under relatively mild conditions compared to other reported MOF-based catalysts.It shows excellent universality for substrates with various substitutions on the N atom or benzene ring.Investigation of the mechanism indicated that the coordination interaction of cobalt metal sites with the nitrogen atoms of aziridines can activate the substrates.For the carboxylative cyclization of CO_(2) with propargylic amines,this catalyst also has a broad substrate scope.Control experiments and nuclear magnetic resonance(NMR)tests suggest that Lewis acid metal sites are responsible for the high catalytic efficiency achieved by activating the alkyne groups.Moreover,1 showed good reusability in both reactions.Compound 1 represents a new catalyst that enables“two birds with one stone”in the catalytic synthesis of oxazolidinones using CO_(2).