机构地区：[1]College of Chemistry,Xiangtan University,Xiangtan 411105,Hunan,China [2]CAS Key Laboratory of Science and Technology on Applied Catalysis,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,Liaoning,China [3]University of Chinese Academy of Sciences,Beijing 100049,China [4]College of Chemistry and Chemical Engineering,Jishou University,Jishou 416000,Hunan,China [5]State Key Laboratory of Heavy Oil Processing,China University of Petroleum,Beijing 102249,China [6]Institute of New Catalytic Materials Science,School of Materials Science and Engineering,Key Laboratory of Advanced Energy Materials Chemistry(MOE),Nankai University,Tianjin 300350,China [7]State Key Laboratory of Catalysis,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,Liaoning,China
出 处：《Chinese Journal of Catalysis》2021年第5期824-834,共11页催化学报（英文）
基 金：中国科学院战略性先导科技专项(XDB17020100);国家自然科学基金(21703238,21690084,21802134);湖南省教育厅优秀青年项目(19B463);锰锌钒产业技术湖南省2011协同创新中心(MXF202001);吉首大学人才启动基金(21).
摘 要：The catalytic hydrogenation of halonitroarenes to haloanilines is a green and sustainable process for the production of key nitrogen-containing intermediates in fine chemical industry.Chemoselective hydrogenation poses a significant challenge,which requires the rational design of the catalysts with proper hydrogenation ability for nitro group and simultaneously preventing dehalogenation of halogen group.Herein,a highly effective Rh@Al_(2)O_(3)@C single-atom catalyst(SAC)was developed for the hydrogenation of m-chloronitrobenzene(m-CNB)to m-chloroaniline(m-CAN),through an in-situ grafting of metal during the assembly of MIL-53(Al),followed by confined pyrolysis.Extensive characterizations reveal an exquisite structure of the Rh@Al_(2)O_(3)@C,containing atomically dispersed Rh sites onto Al_(2)O_(3) confined by the amorphous carbon.The five-coordinated aluminum(Al^(Ⅴ))species are essential for achieving the atomic dispersion of Rh atoms,providing the unsaturated coordinative sites for metal.Compared to the benchmark Rh/γ-Al_(2)O_(3) and Rh/C nanocatalysts,the Rh@Al_(2)O_(3)@C SAC affords an excellent turnover frequency of 2317 molm-CNB·molRh^(–1)·h^(–1),the highest value to date in heterogeneous catalyst systems for the hydrogenation of m-CNB at 313 K and 20 bar H2,together with a sustained selectivity to m-CAN(~98%)during five consecutive runs.The superior catalytic performance of the Rh@Al_(2)O_(3)@C is attributed to a proper modulation of electronic structure of hydrogenation metal by forming SAC,together with an enhanced accessibility of acid function sites.卤代苯胺是化学工业中重要的中间体,主要用于制造药物、聚合物、染料等含氮化学品,用多相金属催化剂催化卤代硝基芳烃加氢制备卤代苯胺是一种高效,绿色和可持续发展的生产工艺.该过程需要选择性加氢硝基基团,同时避免卤素基团的脱卤副反应发生.然而,化学选择性加氢存在巨大的挑战,难点在于催化剂的精准设计,一方面要求具备对硝基基团合适的加氢能力,另一方面要阻止对卤素基团的脱卤副反应发生.基于此,研制高效多相金属催化剂用于卤代硝基芳烃选择性加氢制备卤代苯胺反应引起了高度关注.近年来,单原子金属催化剂受到越来越多的关注,并在卤代硝基芳烃选择性加氢制备卤代苯胺反应中显现出极大的潜力.本文通过在金属有机骨架材料MIL-53(Al)自组装的过程中将金属Rh原位嫁接其骨架结构中,继而通过限域热解的方法制备了Rh@Al_(2)O_(3)@C单原子催化剂,其在间氯硝基苯(m-CNB)加氢制间氯苯胺(m-CAN)反应中显现了高效催化选择性.球差校正高角度环形暗场模式的透射电镜,CO作为探针分子的红外光谱和X射线光电子能谱等结果发现,Rh是以单原子的形式均匀的分布在Al_(2)O_(3)上并被无定型碳包覆,且Rh化学价态呈正价.而27Al固体核磁共振与密度泛函理论计算的结果则进一步确定Al_(2)O_(3)@C载体中存在的五配位的Al物种(Al^(Ⅴ))是锚定Rh单原子的主要位点,Al^(Ⅴ)的不饱和的配位结构可以有效地稳定Rh单原子,对形成Rh位点的单原子分散至关重要.在间氯硝基苯选择性加氢制间氯苯胺反应中,与等体积浸渍法制备的Rh/C和Rh/γ-Al_(2)O_(3)纳米催化剂相比,Rh@Al_(2)O_(3)@C单原子催化剂表现出优异催化性能:其在313 K,氢气压力为20 bar的温和条件下转换频率(TOF)高达2317 molm-CNB·molRh^(–1)·h^(–1),优于已报道的多相金属催化剂,是目前的最高值.此外,该催化剂展现出极佳的稳
关 键 词：Single-atom catalyst RHODIUM Metal-organic framework Hydrogenation CHEMOSELECTIVITY
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