Lan-Lan Lou,Shanshan Li,Huanling Du,Jiong Zhang,Wenjun Yu,Kai Yu,Shuangxi Liu
Graphical Short support : A short-mesochannel SBA-15 material is applied to the immobilization of a chiral 9-amino epicinchonine iridium catalyst, which exhibit excellent catalytic activity and notably improved enantioselectivity for the asymmetric transfer hydrogenation of aromatic ketones. A short-mesochannel SBA-15 material functionalized with propylthiol groups was prepared by co-condensation and applied to the immobilization of chiral 9-amino epicinchonine. After complexing with [Ir(cod)Cl] 2 (cod=1,5-cyclooctadiene), these mesoporous materials were evaluated as catalysts for the asymmetric transfer hydrogenation of aromatic ketones. Higher enantioselectivities and comparable, or even higher, catalytic activities were achieved compared with the free catalyst. Both the short mesochannel and co-condensation approach for short-mesochannel SBA-15 materials functionalized with propylthiol groups, [SSBA-SH( x )] materials were demonstrated to contribute to the excellent catalytic performance. In addition, the catalyst SSBA-AEC(5)/Ir (AEC=9-amino epicinchonine), with low 3-mercaptopropyltrimethoxysilane (MPTMS) content, showed the best catalytic performance; a high enantiomeric excess of 84 % (homogeneous ee =60 %) along with a conversion of 97 % was achieved within 1 h for asymmetric transfer hydrogenation of acetophenone. Moreover, these immobilized catalysts showed high stability during the reaction and could be recovered for reuse.
Hydrothermal is common process for synthesizing well-ordered mesoporous silica, however, it costs time and energy simultaneously. To improve the efficiency of synthesis process, it is necessary to propose a facile synthesis strategy with less time and energy requirement. In this study, an innovative non-hydrothermal method using NH 3 ∙H 2 O as catalyst after ripening step is developed to prepare SBA-15 with short mesochannels (SSBA-15) for the first time. The synthesis period of SSBA-15 framework was extremely shortened within 40 min under the optimized conditions (30 min of ripening step and 25% of NH 3 ∙H 2 O concentration), while obtained material exhibits well-ordered hexagonal pore structure and fine particle morphology of SSBA-15 (pore length of 250 ± 50 nm and mesopore size of 9.8 nm). This method can also be employed to synthesize conventional SBA-15 successfully. Moreover, the application of SSBA-15 as support of solid amine adsorbents on CO 2 adsorption and well-fitting of experimental CO 2 adsorption data with Avrami and intraparticle diffusion models reveal that the adsorbents combine the advantages of micro-mesoporous structure, short mesochannel and amine reagents (high affinity of CO 2 ), resulting in enhanced molecular diffusion, fast adsorption kinetics and high CO 2 adsorption capacity . Notably, the solid amine adsorbents exhibited excellent regeneration ability during ten adsorption-desorption cycles. This work opens up new opportunities in efficient preparation of materials that require hydrothermal process.
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