大孔-介孔Ag/PDA/MMS复合材料的制备及其催化性能

用双模板法制备了介孔纳米薄膜构筑的毫米级尺寸的大孔-介孔SiO₂(MMS)，通过多巴胺(DA)在其孔道表面氧化自聚合成聚多巴胺(PDA)，得到 PDA 修饰的 MMS(PDA/MMS)，再经 PDA 原位还原 Ag⁺制得大孔-介孔 Ag/PDA/MMS 复合材料。应用扫描电镜、透射电镜、N₂吸附-脱附、X射线光电子能谱、X射线衍射、UV-Vis、FT-IR和热重技术对所制得的材料进行表征。结果表明，MMS兼具纳米介孔材料和宏观尺寸大孔材料的优点。Ag/PDA/MMS在催化还原对硝基苯酚(4-NP)反应中展现出高催化活性，转化频率(TOF)达2.97 min^-1。这归因于其独特的结构：相互连通的大孔孔道大大降低了传质阻力，短孔道的介孔显著增加了活性位点的可达性，大的比表面积为反应物提供了大量的活性位点。而且，毫米级尺寸的Ag/PDA/MMS可以很容易从反应体系中分离出来，在5次循环后仍能将4-NP完全转化为对氨基苯酚(4-AP)。另外，Ag/PDA/MMS对亚甲基蓝(MB)的还原也有良好的催化效果。     

尺寸可控、高热稳定性有序介孔碳Au催化剂的合成

纳米Au催化剂被认为是具有商业价值的用于醇选择氧化的第二代催化剂.这是因为Au氧化还原电势高,化学稳定性好,可抑制易使Pt族元素中毒的胺等的毒化;其次,对于一些特定选择氧化和还原反应而言,具有较优的反应选择性.目前较多的研究集中在调变Au纳米颗粒与氧化物载体的相互作用,获得协同效应.例如,利用CeO2纳米晶为载体,沉积Au纳米颗粒(约3 nm),使CeO2部分还原为非计量比的催化材料,活化氧并获得高选择氧化性能.碳是相对惰性的载体,与Au相互作用力弱,因此可被用于研究Au纳米颗粒本征催化性能.但负载碳金催化剂在焙烧甚至还原过程中易团聚,且在反应中易流失,可能导致活性下降.利用胶体沉积法可获得介孔碳担载纳米Au催化剂,对葡萄糖选择氧化具有很高的催化活性和选择性.但是,制备中使用的保护剂残留经常被忽略.由于立体效应或电子结构调变作用,保护剂可能影响Au催化剂活性或稳定性.我们前期建立了反应单体参与的自组装技术合成功能化介孔碳路线,一步在介孔碳骨架中掺杂氧化物纳米催化剂.本文从介孔催化材料的结构出发,设计“镶嵌”在碳骨架中的纳米Au颗粒.采用配位作用辅助表面活性剂自组装技术,以苯酚和甲醛为碳前体,引入含巯基硅烷偶联剂,通过配位作用稳定金离子,获得尺寸可控介孔碳限域纳米Au催化剂.低温炭化中,由于巯基-金的配位作用阻抑金属移动或团聚,高温下聚合物炭化为相对刚性的碳骨架.此时,Au纳米颗粒被相邻介孔孔墙限制.硅烷偶联剂可除去,不影响碳载体,并可产生丰富二级孔道,获得多级孔道介孔碳材料.X射线衍射和透射电镜结果显示,所合成的催化剂中Au颗粒的尺寸可控,为3-18nm,且具有单分散性,均匀地分散在整个介孔碳骨架中,其含量为1.1-9.0 wt％.金碳催化剂具有有序的二维六方介孔结构.能量散射谱(EDX)也证明了催化剂只含有C,O和Au元素,没有S和Si元素的残留.X射线光电子能谱(XPS)结果显示催化剂表面的Au含量远远低于ICP的测试结果,也证明了Au纳米颗粒分布在介孔碳骨架内,同时只含有C,O和Au元素也与EDX相符.X射线近边吸收谱结果表明,随着颗粒尺寸的减小,Au表面电子性质发生改变.N2吸脱附等温线显示,有序介孔碳金催化剂具有典型的第Ⅳ型曲线,说明孔径分布范围较窄,主孔道尺寸为3.4-5.7 nm.值得注意的是,低压力段吸附量显示明显突跃,暗示其具有一套约为2 nm的次级介孔.所有的催化剂都具有高的比表面积(1269-1743 m2/g)和大的孔体积(0.79-1.38 cm3/g).Au纳米颗粒具有高的热稳定性,在惰性气氛中,即使在600℃也未见明显聚集长大.进一步讨论了合成中影响金纳米颗粒尺寸的重要影响因素.(1)巯基含量:通过调节巯基组分的含量,可以调控催化剂中Au纳米颗粒的尺寸(9-18 nm).需要强调的是,Au纳米颗粒尺寸与巯基在新合成材料中的浓度有关,当巯基含量在所研究的范围中时(1.55-3.06 mmol/g),Au纳米颗粒尺寸仅仅与巯基浓度有关,而与Au浓度无关.(2)硫酸预炭化处理:新合成的材料经过一步硫酸预炭化处理,可以得到尺寸为3 nm的有序介孔碳金催化剂.表征结果证明,经过硫酸预碳化处理,大量表面活性剂被除去,同时聚合物载体发生部分碳化,有助于在后续高温炭化中保护3 nm金颗粒不团聚.尺寸可控、高热稳定性、无配体保护的有序介孔碳负载Au催化剂有望应用在催化和传感器等领域.     

氮掺杂有序介孔碳负载超小尺寸铂纳米颗粒催化硝基苯类化合物选择加氢

氮掺杂有序介孔碳材料不仅具有高的比表面积、大的孔容和均一可调的孔径等优点,其骨架中丰富的氮原子还可以对材料的物理化学性质、配位金属电荷密度等进行调控,是一类优异的催化剂载体.本文利用软模板(嵌段共聚物F127为模板),以间氨基苯酚为碳源和氮前体,制备出较高含氮量(9.58 wt%)和比表面积(417 m2/g),以及规则孔径分布的介孔碳材料.结果表明,制备的材料具有三维立方相结构.以该碳材料作为载体,使用传统浸渍氢气还原的策略负载纳米铂颗粒.发现氮掺杂的载体能够有效控制金属纳米颗粒的尺寸,可实现超小尺寸Pt纳米颗粒的有效负载(1.0±0.5 nm),且纳米颗粒均匀分布于介孔碳材料的孔道中.相比而言,使用相同负载方法的情况下,以不掺氮的介孔碳材料为载体,纳米粒子的尺寸较难控制(4.4±1.7 nm)且会发生孔道外颗粒聚集的情况.研究表明,骨架中的氮原子与金属间弱的相互作用对纳米粒子有稳定作用.这对制备超小尺寸的金属纳米粒子催化剂具有一定的指导意义.此外,由于纳米粒子的尺寸将大大影响催化剂活性中心的暴露程度,进而影响催化剂活性.因此,我们以硝基苯类化合物的氢化反应来评价该催化剂的催化性能.在室温和1 MPa H2的温和条件下,氮掺杂的介孔碳负载催化剂表现出了优异的催化性能.反应0.5 h,对氯硝基苯可完全转化,且选择性高达99%.相比而言,商业化的Pt/C催化剂上反应的转化率和选择性分别为89%和90%.其它传统催化剂的比较,如Pt/SiO2,Pt/TiO2,同样表明,氮掺杂介孔碳负载的催化剂具有更优异的催化性能.在相同反应条件下,Pt/SiO2催化剂只能得到46%的转化率和93%的选择性,而Pt/TiO2催化剂虽然能够实现完全转化,但选择性也仅为91%.由此可见,氮掺杂的负载催化剂可大大提高反应活性和选择性,能有效抑制脱氯现象的发生.这种高的催化性能可能与催化剂的介孔结构、氮功能化载体以及超小尺寸的Pt纳米粒子的稳定有关.由于氮原子和介孔孔道的限域作用,氮掺杂介孔碳负载的催化剂也具有良好的催化稳定性,循环使用10次后,催化活性和选择性几乎没有下降.结果表明,循环使用后的催化剂金属粒子尺寸变化不大,进一步表明氮掺杂介孔碳载体对金属纳米颗粒的稳定作用.     

介孔碳纳米纤维制备与超电容性能研究

采用低分子量酚醛树脂/F127混合物填充多孔氧化铝模板孔道,制备了大尺寸介孔孔道、核-壳结构的介孔碳纳米纤维.分别以SEM、TEM及N2等温吸附-脱附观察分析样品形貌和孔结构参数.循环伏安与恒流充放电测定该介孔纳米纤维电极(阳极)的超电容性能.结果表明:介孔碳纳米纤维比电容明显增大,且在高扫速、大电流下具有良好的超电容特性.     

PDA/SiO2大孔复合材料固定化荧光假单胞菌脂肪酶

以具有三维骨架结构的大孔聚合物为模板制备SiO_2大孔材料,通过多巴胺在SiO_2大孔材料孔道表面的原位聚合制得聚多巴胺表面功能化修饰的二氧化硅大孔材料(PDA/SiO_2)。应用SEM、EDX、MIP、BET、TG-DTA和FTIR等技术对修饰前后的材料进行表征。以PDA/SiO_2为载体固定荧光假单胞菌脂肪酶(PFL),优化固定化条件并对比游离脂肪酶和固定化脂肪酶的性质。结果表明SiO_2大孔材料具有三维连续贯通的孔道结构,孔径分布在300~500 nm,聚多巴胺修饰后形成聚多巴胺/二氧化硅复合纳米薄膜构筑的大孔材料。在固定化时间为14 h、p H值为8、初始脂肪酶浓度为0.4 mg·m L-1时,固定化效果最佳,酶活回收率达246%。与游离脂肪酶相比,固定化脂肪酶有更宽的温度和p H适用范围、热稳定性显著提高,并展现出良好的储存稳定性和操作稳定性,固定化脂肪酶的Km低于游离脂肪酶的,酶与底物的亲和性较好。     

镍氮掺杂有序大孔/介孔碳负载银纳米颗粒用于高效电催化CO2还原

多组分体系中的协同作用为设计高效的二氧化碳还原电催化剂提供了新的思路. 本工作通过双模板法和化学还原法精心设计制备了大孔/介孔镍氮掺杂碳(Ni-N-OMMC)负载银纳米颗粒复合材料(Ag/Ni-N-OMMC), 用于高效电催化还原CO₂为CO. 此复合材料表现出良好的电催化活性, 在CO₂饱和的0.1 mol•L^–1 KHCO₃电解液中, 电位为–1.0 V (相对于可逆氢电极, RHE)时CO的电流密度(J_CO)高达33.29 mA•cm^–2. 并具有较宽的工作电压范围, 在–0.7~–1.0 V (vs. RHE)下, CO的法拉第效率超过90%. 其优异的电催化性能可能归因于Ag纳米颗粒与具有丰富Ni-N _x活性位点的Ni-N-OMMC载体之间的协同效应, 以及三维互联有序大孔/介孔结构提供的高比表面积和高效的质量/电荷传输.     

Schiff碱改性法制备SBA-15型介孔分子筛负载的纳米氧化镍

基于Schiff碱功能单体的改性作用,采用共缩聚方法,制备了SBA-15型介孔分子筛负载的氧化镍纳米粒子。 采用小角X射线散射（small angle XRD）、广角X射线衍射（wide angle XRD）、紫外-可见光谱（UV-Vis）、高分辨透射电子显微镜（HRTEM）和N2吸附-脱附测定对制得的样品进行了表征。 结果表明,制得的样品具有SBA-15型介孔分子筛典型的二维六方有序结构,NiO纳米粒子主要分布于SBA-15型介孔分子筛的孔道内。 当功能单体的含量不超过10%时,SBA-15型介孔分子筛的孔径在6~8 nm范围内;而当功能单体的含量达到15%时,SBA-15型介孔分子筛的孔道被严重堵塞,孔径降为3.8 nm。 NiO纳米粒子的尺寸随着功能单体含量的增加而增大。     

三维有序大孔复合材料Ag/TiO2的制备与不同模式下的光催化性能

采用聚苯乙烯(PS)微球和EO20PO70EO20(P123)作为模板剂,通过溶胶-凝胶及煅烧后处理等方法制备了三维有序大孔复合材料Ag/TiO2(3DOM Ag/TiO2).经傅里叶变换红外光谱、X射线衍射、紫外-可见漫反射吸收光谱、X射线光电子能谱、N2吸附-脱附测试和扫描电子显微镜配合X射线能量色散谱等测试手段对其组成、结构及形貌等进行了表征.结果显示,该复合材料的孔结构排列整齐有序,孔壁呈现介孔结构且分布均匀,属于三维有序大孔材料.该3DOM Ag/TiO2具有锐钛矿晶相,其Ag以单质形式存在.与商用光催化剂(Degussa P-25)相比,3DOM Ag/TiO2对光的吸收红移至可见区.考察了3DOM Ag/TiO2在紫外光、可见光以及微波辅助等不同模式下光催化降解有机污染物的性能.结果显示,其活性明显高于P-25和Ag/TiO2,且针对不同类型的有机污染物均表现出较好的光催化性能.     

孔道三维相互连通锐钛矿TiO2-SiO2纳米复合介孔材料的制备及其高光催化活性

本文报道一种孔道三维相互连通锐钛矿TiO2-SiO2纳米复合介孔材料的制备.该介孔材料是以两维六方有序结构、直孔道、锐钛矿70TiO2-30SiO2-950纳米复合介孔材料(于950oC晶化2 h)为前驱体, NaOH为SiO2的刻蚀剂,通过“在孔壁内造孔”的方法获得.我们的策略是采用温和的造孔条件,如稀NaOH溶液,合适的温度与固/液比等.采用X射线衍射(XRD),透射电镜(TEM)和低温N2吸附等技术对样品的介孔结构进行了系统表征.结果表明,墙内孔的密度非常高,孔径均一(平均尺寸3.6 nm),且在三维网络高度连通原孔道,但介孔结构仍保持其完整性.锐钛矿纳米晶粒的结晶度和大小在墙内造孔前后基本保持不变.该材料光催化降解罗丹明B(0.303 min–1)与亚甲基蓝(0.757 min–1)的活性相当高,此活性分别是其母体材料的5.1和5.3倍,甚至是Degussa P25光催化剂的16.5和24.1倍.这充分表明三维连通孔道结构对活性的大幅提高起了关键作用.孔道三维连通式锐钛矿TiO2-SiO2纳米复合介孔材料对上述污染物展现出意想不到的高降解活性,显著高于迄今已报道的金属氧化物基介孔材料对上述污染物的降解活性.更重要的是,该光催化剂具有相当高的稳定性和重复使用性.相信,本方法将为具有超高性能的孔道三维相互连通其它金属氧化物基介孔材料的制备铺平了道路.
　　小角XRD结果表明,母体材料的孔道是两维六方有序结构,在孔壁内造孔之后,样品原有的介孔结构仍保持其规整性.宽角XRD结果显示,二氧化钛的晶相是锐钛矿,晶粒尺寸为10.8 nm.造新孔之后,锐钛矿纳米晶粒的结晶度和大小与母体样品的相比变化不大. TEM结果显示,母体样品的孔壁内没有孔.孔道是两维六方有序排列的直孔道,孔径大小均一(平均尺寸4.1 nm).高分辨透射电镜(TEM)观察揭示,锐钛矿纳米晶粒(平均大小11.3 nm)在孔壁内随机排列,并与无定形SiO2纳米颗粒相互连接,相间共存,形成类似“砖块?水泥砂浆”砌成的孔壁,这种独特的复合骨架结构赋予其很高的稳定性.当一些SiO2纳米颗粒被去除之后, TEM观察显示,孔壁内有密集分布的孔,这些孔取向随机,并在三维方向连通原孔道,但介孔骨架结构仍保持其完整性.墙内孔的大小范围很窄(3.1?4.3 nm),平均大小为3.6 nm.高分辨TEM观察显示,锐钛矿晶粒大小与母体材料内的相比基本未变.上述结果与XRD结果一致.低温N2吸附表征结果显示,母体样品内只有一种孔道,孔径为4.0 nm.去除部分SiO2后的样品内有两种孔道,孔径分别是3.4和4.1 nm.这些结果与TEM的观察吻合.罗丹明B与亚甲基蓝在造孔前后样品内扩散速率评价结果显示,其在三维连通孔道内的扩散速率很高,大约是其母体材料内的5倍以上.这表明相互连通的孔道网络结构非常有利于客体分子在其内扩散.光催化降解性能评价结果显示,罗丹明B与亚甲基蓝在相互连通孔道内降解的速率相当高,分别是其在不连通孔道内的5.1和5.3倍.这充分证明孔道三维相互连通对活性的大幅提高起了关键作用.我们对材料的稳定性和重复使用性作了评价,经过10次循环使用孔道三维相互连通锐钛矿TiO2-SiO2纳米复合介孔材料,其吸附与光催化降解罗丹明B的性能变化不大.这充分证明本文制备的孔道连通复合介孔材料的性能是相当稳定的和可重复使用的.该方法可用于制备具有超高性能的孔道三维相互连通其它金属氧化物基介孔材料,如Nb2O5, Ta2O5等.     

双模板法合成介孔/大孔二级孔道碳材料

以酚醛树脂低聚物为前驱物, 利用双模板法制备了具有介孔/大孔双孔结构的碳材料. 其中以二氧化硅蛋白石为大孔模板, 以嵌段共聚物自组装结构为介孔模板. 对样品进行了扫描电子显微镜(SEM), 透射电子显微镜(TEM), X射线衍射(XRD)和氮气吸附-脱附实验表征. 结果表明所制备的双孔碳材料大孔直径约为230 nm, 介孔直径10 nm.     

Desilication mechanism revisited: highly mesoporous all-silica zeolites enabled through pore-directing agents

The role of pore‐directing agents (PDAs) in the introduction of hierarchical porosity in silicalite‐1 in alkaline medium was investigated. By incorporation of various PDAs in aqueous NaOH, homogenously distributed mesopores were introduced in 2.5 μm silicalite‐1 crystals. It was proven for the first time that framework aluminum is not a prerequisite for the introduction of intracrystalline mesoporosity by desilication. The pore‐directing role is not directly exerted by framework trivalent cations metals, but by species on the external surface of the zeolite. The inclusion of metal complexes (Al(OH)₄^?, Ga(OH)₄^?) and tetraalkyl ammonium cations (tetramethyl ammonium (TMA⁺), tetrapropyl ammonium (TPA⁺)) in the alkaline solution led to distinct mesopore surface areas (up to 286 m² g^?1) and pore sizes centered in the range of 5–20 nm. In the case alkaline treatment was performed in the presence of Al(OH)₄^?, all aluminum partially integrated in the zeolite giving rise to both Lewis and Brønsted acidity. Apart from the concentration and location, the affinity of the PDA to the zeolite surface plays a crucial role in the pore formation process. If the PDA is attracted too strongly (e.g., TMA⁺), the dissolution is reduced dramatically. When the pore‐directing agent is not attracted to the zeolite’s external surface, excessive dissolution occurs (standard alkaline treatment). TPA⁺ proved to be the most effective PDA as its presence led to high mesopore surface areas (>200 m² g^?1) over a broad range of PDA concentrations (0.003–0.1 M ). Importantly, our results enable to extend the suitability of desilication for controlled mesopore formation to all‐silica zeolites.     

Development of porous and dispersed CRM

Porous and finely dispersed certified reference materials (CRM) were certified using the gas adsorption method. The special certification procedure for IUPAC isotherm classification types I, II, and IV is presented for meso- and macroporous materials with special emphasis on specific surface area, specific pore volume and pore width according to standards DIN 66 131, 66 134, and 66 135. Four CRMs (SiO₂, α-Al₂O₃, two transition aluminas) with a macro- and mesopore range are presented. Certification was made on the basis of BCR guidelines in connection with interlaboratory tests (altogether 38 participating laboratories, 44 various gas adsorption apparatus). Received: 25 April 1997 / Revised: 22 August 1997 / Accepted: 28 August 1997     

三维有序大孔-介孔二氧化硅的可控制备及表征

以聚甲基丙烯酸甲酯(PMMA)胶晶为大孔模板、嵌段共聚物P123为介孔模板,利用双模板剂法进行了三维有序大孔-介孔二氧化硅材料的制备研究。采用SEM、TEM、低角XRD以及N₂吸脱附技术对样品进行了表征。结果表明,通过简单的调控PMMA胶晶模板的组装过程,就可以调变合成材料中的大孔结构,从而轻松地实现可控的制备出具有网状或者层状结构的三维有序大孔-介孔二氧化硅材料,并提出了其可能的形成机理。此外,所制备的三维有序大孔-介孔二氧化硅样品均具有较大的BET比表面积(>550m₂·g^-1),大孔孔径200nm左右,介孔孔径分布集中于3.5nm左右。     

DFT Study of the BH4− Hydrolysis on Au(111) Surface

The mechanism of the catalytic hydrolysis of BH₄⁻ on Au(111) as studied by DFT is reported. The results are compared to the analogous process on Ag(111) that was recently reported. It is found that the borohydride species are adsorbed stronger on the Au⁰-NP surface than on the Ag⁰-NP surface. The electron affinity of the Au is larger than that of Ag. The results indicate that only two steps of hydrolysis are happening on the Au(111) surface and the reaction mechanism differs significantly from that on the Ag(111) surface. These remarkable results were experimentally verified. Upon hydrolysis, only three hydrogens of BH₄⁻ are transferred to the Au surface, not all four, and H₂ generation is enhanced in the presence of surface H atoms. Thus, it is proposed that the BH₄⁻ hydrolysis and reduction mechanisms catalyzed by M⁰-NPs depend considerably on the nature of the metal.     

An efficient and easily retrievable dip catalyst based on silver nanoparticles/chitosan-coated cellulose filter paper

Re-use of a catalyst is an important task, which is usually achieved by loading it on easily separable supports such as magnetic substrates. However, we demonstrate here the process of easy and fast catalyst separation from a reaction medium by loading it onto an economically feasible and microscopically high surface substrate of filter paper (FP) made up of cellulose microfibers as catalyst support. To achieve the goal, we coated chitosan (CH) on filter paper (CH-FP) to impart a high affinity of the substrate for metal ion absorption. AgNO₃ dissolved in water with a 0.1 M concentration was used as the Ag ion carrier solution, and CH-FP strips with known rectangular dimensions were submerged into it for the metal ion absorption. The metal ion-laden CH-FP strips were dip treated with sodium borohydride (NaBH₄) aqueous solution to prepare Ag-nanoparticle loaded CH-FP (Ag/CH-FP). X-ray diffraction and energy dispersive X-ray spectroscopy confirmed the formation of the Ag/CH-FP hybrid. Ag/CH-FP morphology was examined through scanning electron microscopy analysis, which showed the presence of Ag nanoparticles attached to the cellulose microfibers. The prepared Ag/CH-FP was employed as a dip catalyst for the degradation of nitroarene compounds of 2-nitophenol (2-NP) and 4-nitrophenol (4-NP) by NaBH₄. Remarkably, the rate constants for 4-NP and 2-NP were 3.9 × 10^?3 and 1.7 × 10^?3 s^?1, respectively. In addition, we discussed the ease of the catalyst retrievability from the reaction mixture and its re-usability.     

Preparation of a kind of mesoporous carbon and its performance in adsorptive desulfurization

Carbon materials were prepared using mesoporous silica HMS with different pore sizes as the hard templates and water-soluble phenolic resin as the carbon source. The obtained materials were characterized by powder X-ray diffraction, transmission electron microscopy and N₂ physical adsorption, and were used in adsorptive desulfurization. It has been shown that the carbon material prepared using HMS with larger pore size (>3 nm) presented uniform wormlike mesopore of 2.3 nm and large BET surface area (1903 m²/g). The mesoporous carbon was an excellent adsorbent to remove the refractory sulfur compound in diesel, especially dibenzothiophene and 4, 6-dimethyldibenzothiophene.     

三维有序大孔Ag/ZrO2-TiO2：制备及紫外光催化降解染料和水杨酸性能

采用聚苯乙烯(PS)微球作为模板剂,经溶胶-凝胶及煅烧后处理的方法制备了三维有序大孔(3DOM)复合材料Ag/ZrO2-TiO2。通过FTIR、XRD、XPS、N2吸附-脱附和SEM-EDS等对其进行了表征。结果显示,经PS微球作用后的复合材料Ag/ZrO2-TiO2具有锐钛矿晶型结构,其Ag以单质形式存在。该复合材料的孔结构高度有序,属三维有序大孔,平均孔直径为120 nm,孔壁由紧密堆积的Ag/ZrO2-TiO2纳米晶粒组成,孔收缩率约为40%。该复合材料表现出较好的紫外光催化降解水杨酸和甲基橙等染料性能,其活性明显高于商用光催化剂(Degussa P-25)、Ag/ZrO2-TiO2和3DOM ZrO2-TiO2,在90 min内对甲基橙的降解率达80.1%。     

Enhancement of activity and reusability of lipase immobilized on magnetic mesoporous silica for the resolution of racemic secondary alcohols

Magnetic mesoporous silica (MMS) composites with an average mesopore size (~2.98 nm), large surface area (404–442 m²/g), and high saturated magnetization (17.7–33.5 emu/g) were successfully prepared by hydrothermal crystallization in the presence of monodisperse Fe₃O₄ microspheres. The as‐synthesized composites served as supports for lipase from Burkholderia cepacia (BCL) immobilization in isooctane via interfacial activation and were then employed as biocatalysts for the transesterification resolution of racemic aromatic secondary alcohols to synthesize chiral intermediates. The catalytic performance of the immobilized BCL (BCL/MMS) was notably improved compared to that of the non‐immobilized BCL, with the total conversion and enantiomeric excess reaching 50 and 99% of the maximum theoretical values, respectively. Furthermore, the magnetic BCL/MMS possessing the same textural properties and enzyme loading exhibited decreasing catalytic capability as their saturated magnetization value increased. Moreover, BCL/MMS could also be readily recycled from the reaction system by applying an external magnetic field so as to facilitate its reuse up to five cycles with retaining up to 90% of the initial activity. Its high activity, easy recovery, and excellent operational stability make the BCL/MMS a potential green catalyst for the synthesis of optically active intermediates.