室温快速合成HKUST-1应用于醇选择性催化氧化
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摘要
利用溶剂诱导成核法,将HKUST-1前驱液滴加入甲醇溶液,在室温条件下即可快速合成HKUST-1晶体。X-射线衍射结果表明所合成的HKUST-1具有很高的结晶度;扫描电子显微镜显示该HKUST-1具有规则的八面体形貌,尺寸为2～3μm; N2吸附实验表明HKUST-1的BET比表面积高达1 100 m2/g。利用HKUST-1含有大量的未饱和Cu2+,以HKUST-1和2,2,6,6-四甲基哌啶氧自由基(TEMPO)组成的催化体系,研究了HKUST-1/TEMPO对苯甲醇选择性氧化成苯甲醛的反应。催化结果表明,HKUST-1/TEMPO体系在无外加碱添加剂时,在三氟甲苯溶剂中,可将苯甲醇高效、高选择性氧化成苯甲醛。HKUST-1和TEMPO均是催化苯甲醇转化成苯甲醛的催化剂,两者缺一不可。HKUST-1催化前后结构未发生明显变化,催化剂循环利用4次后,对苯甲醇的转化率仍保持在80%以上,是优异的异相催化剂。
By using solvent-induced crystallization method,HKUST-1 microcrystals were synthesized simply by dropping HKUST-1 precursor into methanol under stirring at room temperature. Powder XRD results indicated that the obtained HKUST-1 crystals are highly crystalline materials; SEM images shown that HKUST-1 are octahedral shape with uniform size in a range of 2 ～ 3 μm; N2 adsorption/desorption isotherm revealed that HKUST-1 crystals are highly porous with BET specific surface areas up to1 100 m2/g. By taking advantage of the abundance of open Cu2 +sites,HKUST-1/TEMPO catalytic system was developed for selective oxidation of alcohols. Interestingly,HKUST-1/TEMPO system shows high efficient and excellent selectivity toward the oxidation of benzyl alcohol to benzadehyde. The HKUST-1 crystals and TEMPO radicals were found both to be crucial for the catalysis. The conversion of benzyl alcohol remains 80% within the four runs of catalytic reactions,and the crystallinity and morphology of HKUST-1 crystals show negligible change,highlighting the excellent catalytic active of HKUST-1 and potential applications in heterogeneous catalysis.
By using solvent-induced crystallization method,HKUST-1 microcrystals were synthesized simply by dropping HKUST-1 precursor into methanol under stirring at room temperature. Powder XRD results indicated that the obtained HKUST-1 crystals are highly crystalline materials; SEM images shown that HKUST-1 are octahedral shape with uniform size in a range of 2 ～ 3 μm; N2 adsorption/desorption isotherm revealed that HKUST-1 crystals are highly porous with BET specific surface areas up to1 100 m2/g. By taking advantage of the abundance of open Cu2 +sites,HKUST-1/TEMPO catalytic system was developed for selective oxidation of alcohols. Interestingly,HKUST-1/TEMPO system shows high efficient and excellent selectivity toward the oxidation of benzyl alcohol to benzadehyde. The HKUST-1 crystals and TEMPO radicals were found both to be crucial for the catalysis. The conversion of benzyl alcohol remains 80% within the four runs of catalytic reactions,and the crystallinity and morphology of HKUST-1 crystals show negligible change,highlighting the excellent catalytic active of HKUST-1 and potential applications in heterogeneous catalysis.
引文
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[3] Eddaoudi M,Kim J,Rosi N,et al. Systematic design of pore size and functionality in isoreticular MOFs and their application in methane storage[J]. Science,2002,295(5554):469-472.
[4] Furukawa H,Cordova K E,O'Keeffe M,et al. The chemistry and applications of metal-organic frameworks[J].Science,2013,341(6149):1230444.
[5]魏文英,方键,孔海宁,等.金属有机骨架材料的合成及应用[J].化学进展,2005,17(6):1110-1115.
[6]林之恩,杨国昱.多孔材料化学:从无机微孔化合物到金属有机多孔骨架[J].结构化学,2004,23(12):1388-1398.
[7] Zhang J P,Zhang Y B,Lin J B,et al. Metal azolate frameworks:from crystal engineering to functional materials[J]. Chemical Reviews,2012,112(2):1001-1033.
[8]田玉雪,许佩瑶,汪黎,等.金属有机框架化合物应用于催化反应研究进展[J].应用化工,2018,47(4):810-812.
[9] Sachse A,Ameloot R,Coq B,et al. In situ synthesis of Cu-BTC(HKUST-1)in macro-/mesoporous silica monoliths for continuous flow catalysis[J]. Chemical Communications,2012,48(39):4749-4751.
[10] Toyao T,Styles M J,Yago T,et al. Fe3O4@HKUST-1 and Pd/Fe3O4@HKUST-1 as magnetically recyclable catalysts prepared via conversion from a Cu-based ceramic[J]. Cryst Eng Comm,2017,19(29):4201-4210.
[11] Sheldon R A. Recent advances in green catalytic oxidations of alcohols in aqueous media[J]. Catalysis Today,2015,247:4-13.
[12] Parmeggiani C,Matassini C,Cardona F. A step forward towards sustainable aerobic alcohol oxidation:new and revised catalysts based on transition metals on solid supports[J]. Green Chemistry,2017,19(9):2030-2050.
[13] Palmisano G,Ciriminna R,Pagliaro M. Waste-free electrochemical oxidation of alcohols in water[J]. Advanced Synthesis&Catalysis,2006,348(15):2033-2037.
[14]杨贯羽,郭彦春,武光辉,等.氮氧自由基TEMPO:选择氧化醇的高效有机小分子催化剂[J].化学进展,2007,19(11):1727-1735.
[15] Sheldon R A,Arends I W C E. Organocatalytic oxidations mediated by nitroxyl radicals[J]. Advanced Synthesis&Catalysis,2004,346(910):1051-1071.
[16] Ryland B L,Stahl S S. Practical aerobic oxidations of alcohols and amines with homogeneous copper/TEMPO and related catalyst systems[J]. Angewandte Chemie International Edition,2014,53(34):8824-8838.
[17] Dhakshinamoorthy A,Alvaro M,Garcia H. Aerobic oxidation of benzylic alcohols catalyzed by metal-organic frameworks assisted by TEMPO[J]. ACS Catalysis,2010,1(1):48-53.