作者通过项目号码承认瑞士国家科学基金会（SNF）的财务支持。 200021_160174。

主模具制造<ol><li>执行4英寸硅母模的光刻制造，如前面详细描述的19 ;本研究中使用的主模具使用相同的方案制造。 注意:微流控器件通常通过多步法制造。第一步是使用传统绘图软件设计微流体通道。然后，产生含有微流控网络的高分辨率薄膜光掩模，其特征精度为约5μm。接下来，通过标准光刻技术在4英寸硅晶片上制造母模。在目前的研究中，采用SU-8作为负型光致抗蚀剂来制造母模。在我们的设备中，SU-8结构的高度定义为50μm。最后，通过直接浇铸透明聚合物（通常是聚二甲基硅氧烷）来制造微流体装置羟基硅氧烷（PDMS）。 </li></ol> 2.单层微流体装置的制造注意:协议要求在70°C下进行烤箱操作。在开始制造方案之前，烘箱的温度应稳定在70℃。较低的温度可能导致粘结不良和非功能性的设备。 <ol><li>将制作的主模具放入装有真空泵的干燥器中。然后，将100μL氯代三甲基硅烷倒入玻璃小瓶中，并将其放入干燥器中。 注意:注意！氯代三甲基硅烷是一种腐蚀性，危险和有毒物质。因此，所有的处理步骤应在通风通风橱下进行，并且必须佩戴合适的护目镜，手套和实验室外套。 </li><li>关闭干燥器并置于真空下（本实验中为51毫巴）。等待至少1小时以确保蒸发的氯代三甲基胺的沉积在模具表面的硅烷。 1小时后，轻轻打开干燥器的空气阀将其平衡至大气压力并将其打开。 注意:注意！干燥器打开一旦氯三甲基硅烷蒸气泄漏出来;不要直接在干燥器上方呼吸，并且始终在通风柜中执行上述操作。 </li><li>手动取出硅胶模具，并关闭干燥器。将主模具存放在封闭的箱体（或层流罩内），以避免颗粒在其表面上沉积。 注意:所有进行的步骤必须在均匀空气速度下运行的层流罩下进行。 </li><li>在一次性杯中制备PDMS预聚物和固化剂（重量比为10:0.9）的混合物，并用塑料刮刀剧烈混合。作为指导，使用20g弹性体和1.8g固化剂来制造大约5mm厚的四个PDMS微流体装置。 </li><li>放置含有混合好的PD的杯子MS在干燥器中在真空下脱气并除去气泡。一旦PDMS脱气，打开干燥器并取出杯子。 注意:在本实验中，在51毫巴下大约需要30分钟。 </li><li>轻轻地将四个正方形框架（ 例如 ，内部尺寸为24 mm x 24 mm的聚四氟乙烯（PTFE）框架）放置在主模具上，以使每个框架在主模具上形成围绕单个图案化结构的壁。 </li><li>将脱气的PDMS倒入框架中，并将母模顶部倒入充满状态。将带有方形框架的母模置于70℃的烘箱中2小时。 </li><li> 2小时后，从烤箱中取出母模，将组件放冷至室温。 </li><li>通过将它们与主模具仔细分离并将PDMS芯片滑出正方形框架，手动剥离结构化PDMS板（或PDMS芯片）和方框。 </li><li>冲孔入口和出口孔使用1.5 mm活检穿孔机在设计中， 例如 ，在微流体通道结束时的位置。切割多余的PDMS，并使用胶带从结构化PDMS芯片表面清除任何碎屑。 </li><li>将PDMS芯片（开放通道朝上）以及玻璃盖玻片放入等离子体发生器的腔室并关闭腔室。 </li><li>将等离子体发生器置于真空下（1.4 mbar）;将等离子体发生器切换1分钟。 </li><li> 1分钟后，关闭等离子体发生器，通风室，取出处理过的PDMS芯片和玻璃盖玻片。将PDMS芯片（从结构化通道的一侧）和玻璃盖玻片结合在一起以封闭通道;此时制造单层微流体装置。 </li><li>最后，将粘合的微流体装置放置在70℃的烘箱中至少4小时，以增强PDMS和玻璃之间的粘合。 </li></ol>准备微流体装置和前体溶液的离子<ol><li>在乙酸中制备0.040 M BTCA溶液。 注意:注意！乙酸是一种危险的，腐蚀性和易燃的化合物，其蒸气对眼睛和呼吸系统极度刺激。因此，处理步骤必须在通风橱中进行。此外，使用者必须戴上保护性实验衣，护目镜和手套。 </li><li>制备0.040 M的TAPB溶液在乙酸中。 注意:本实验中使用的微流体装置有四个入口通道（ 图1B和图2 ）。 </li><li>将BTCA和TAPB溶液装入两个不同的注射器（5 mL注射器，此处装有3 mL溶液），将注射器放入并固定到注射泵上，并将其连接到制造的微流体芯片的两个中间入口（每个入口一个试剂），使用PTFE管（内径0.8 mm）。 </li><li>用纯的另外两个注射器装载乙酸（这里是5 mL注射器完全装满），将注射器放入并固定到注射器泵上，并使用相同类型的PTFE管将其连接到微流控芯片的两个入口。 </li><li>将足够长的PTFE管（在当前实验中，约15厘米）连接到微流体芯片的出口。使用计算机控制的注射泵来激励流体流动，如以下步骤所述。 </li></ol>连续合成MF-COF纤维<ol><li>使用注射泵每次以100μL/ min的流速引入两根乙酸溶液，鞘流位于试剂流的外侧（ 图2 ）。 </li><li>等待1分钟，通过两个中间入口（每个入口一个试剂）分别以50μL/ min的流速注入两种试剂（TAPB和BTCA）。等待1分钟，直到稳定的流量建立。 </li><li>观察黄色纤维微结构的形成先前通过傅立叶变换红外（FT-IR）光谱，元素分析和固态13 C CP-MAS-NMR 6表征为MF-COF的固体;在这些条件下，MF-COF的形成不是连续的。 </li><li>将TAPB和BTCA的流速提高到200μL/ min，并保持醋酸的两个鞘流速100μL/ min。现在等待1分钟直到流量稳定。观察黄色MF-COF纤维的高度浓缩悬浮液的形成，最终导致出口堵塞。 </li><li>由于芯片和出口管现在不起作用，请使用新的芯片，并根据步骤3.3-3.6进行实验准备。 </li><li>以100μL/ min的流速引入两根乙酸鞘，并等待1分钟。将TAPB和BTCA的流量分别设置为100μL/ min，观察连续的黄色MF-COF纤维的形成。 </li><li>将管子的出口放在含有醋的培养皿中酸酸。例如，将10mL乙酸放入玻璃培养皿（直径60mm）中。一旦合成的纤维离开位于微流体装置的出口处的管，将管移动到表面上以便于连续MF-COF纤维的排出。 </li></ol>直接打印2D和3D MF-COF结构注意:由于合成纤维可能不完全均匀，必须调整沉积速度以确保连续印刷。 <ol><li>按照第3节所述准备微流体装置，并以100μL/ min的流速注入所有四种溶液。 </li><li>等待1分钟，直到流稳定，合成的MF-COF纤维离开位于微流体装置出口处的管。在位于微流体装置出口处的管的出口旁边准备一个干净的基材，用于直接印刷MF-COF纤维。 注意:在我们的调查中，24毫米所有印刷实验都采用x 76毫米玻璃盖玻片。 </li><li>将管连接到微流体装置的出口，使其端部比玻璃盖玻片高出几毫米。缓慢地将管子移动到玻璃盖玻片上，以方便MF-COF纤维的排出并避免聚集。 </li><li>一旦流动稳定，缓慢地将位于微流体装置出口处的管子从玻璃盖玻片大约2-3厘米处提起，以观察独立且稳定的MF-COF纤维。 </li><li>要继续打印，请将管道的出口朝玻璃盖玻片移回，并手动将管子移动到表面上，以绘制所需的2D或3D MF-COF结构。 </li></ol>

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作者没有什么可以披露的。

这里报道的基于微流体的合成方法提供了一种用于在表面上直接印刷COF材料的新颖且简单的方法。使用单层微流体装置进行合成，该装置包括与玻璃盖玻片接合的微流体PDMS芯片。微流体装置的制造可以通过PDMS相对于硅母模的常规铸造并随后将PDMS与压印的微通道对接在玻璃盖玻片上来实现。 为了成功组装微流体装置，重要的是在洁净室环境中制造母模以避免在光刻期间的污染和缺陷。由于不合适的条件，缺陷的主模具将导致非功能微流体装置。此外，PDMS预聚物与固化剂的比例，其控制PDMS的刚度已经被优化以制造鲁棒的PDMS偏差ces仍然有足够的弹性。 PDMS芯片的弹性在促进PTFE管道稳定插入微流体装置的入口和出口孔中是重要的。 存在于微流体装置中的层流条件允许精细控制在共流动试剂流之间的界面处发生的化学反应。促进内部微流体装置的剂型的先进混合主动地有助于形成和分离通过其他合成方法6,21,22,23不可及的微结构和纳米结构。在本研究中，我们还显示微流体合成可以导致形成具有互连的纤维微结构的3D海绵状COF材料，这与通过常规体积合成方法获得的COF材料不同。 6 。然而，微流体合成有助于形成可连续印刷在不同表面上的宏观和多孔MF-COF纤维。这种合成和直接印刷的新方法在COF研究中创造了新的机会。

共价有机骨架（COFs）是一类已知的多孔和结晶材料，其中有机结构单元通过共价键1,2,3,4,5牢固地保持在一起。 COF通常按照超分子化学原理进行组装，其中组成的分子结构单元选择性地反应以限定最终和预定的多孔组件。这种方法允许合成具有受控和有序结构的材料（ 例如 ，具有限定的孔尺寸）和组合物3,6,7,8 。与其他多孔材料相比，COF是独特的，因为它们由轻元素（C，H，B，N和O）组成，并具有可调谐孔<html>精神1，5 。受到这些独特和内在特征的启发，COF已经被评估为在化学分离中的潜在应用9 ，气体储存10和催化11 ，传感器12 ，光电子13 ，清洁能源技术14和电化学能量装置15 。 迄今为止，用于制备COF材料的绝大多数方法是基于溶剂热自缩合和共缩合反应，其中以高温和高压为标准。虽然COF是热稳定的，但它们通常受到有限的加工性能的影响， 即 COF通常是不溶性和不可加工的结晶粉末，这显着地限制了它们在潜在和实际应用范围内的使用ss ="xref"&gt; 2，6，8，16，17。尽管COF合成方面取得了显着的进展，但是在该领域的主要挑战是开发一种能够在适当反应条件（ 如温度和压力）下制备COF的方法，从而可以促进其在表面上的加工性能。 最近研究表明，Shiff碱化学可用于在室温下合成基于亚胺的COF。由于1,3,5-三（4-氨基苯基）苯（TAPB）和1,3,5-苯三甲醛（BTCA） 17 （ 图 ）的快速有效反应，形成了命名为RT-COF-1的COF 1A ）。通过使用平版印刷法在刚性和柔性表面上直接印刷RT-COF-1的微米和亚微米图案来证明该合成方法的功效，喷墨打印技术。最近，利用微流体，我们已经证明了用于连续合成相同亚胺基COF（以下称为MF-COF 6）的纤维的有效方法。与用于生成COF 18的其他报道的合成方法不同，这种基于微流体的合成方法使得能够在几秒钟内在环境温度和压力下快速合成MF-COF纤维。此外，由于合成的MF-COF纤维的机械稳定性，我们已经证明了这种基于微流体的方法如何能够在表面上直接印刷2D和3D结构。在这里，我们证明该方法可用于在具有不同化学和物理性质的各种表面上绘制COF结构。我们认为，这种新方法为不同方向和各种表面上的COF的良好控制图案化和直接印刷打开了新的途径。

<table border="0" cellpadding="0" cellspacing="0" width="1147">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">High resolution film masks</td>
			<td style="width:252px;">Microlitho, UK</td>
			<td style="width:189px;">-</td>
			<td style="width:371px;">Features down to 5um</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Silicon wafers</td>
			<td style="width:252px;">Silicon Materials Inc., Germany</td>
			<td style="width:189px;">4&#34; Silicon Wafers</td>
			<td>Front surface: polished, back surface: etched</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Silicone Elastomer KIT (PDMS)</td>
			<td style="width:252px;">Dow Corning, USA</td>
			<td style="width:189px;">Sylgard 184</td>
			<td>-</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Chlorotrimethylsilane</td>
			<td style="width:252px;">Sigma-Aldrich, Switzerland</td>
			<td style="width:189px;">386529</td>
			<td>&#8805;97%, CAUTION: Handle it only under fume hood.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Biopsy puncher</td>
			<td style="width:252px;">Miltex GmBH, Germany</td>
			<td style="width:189px;">33-31A-P/25</td>
			<td>1.5 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Glass coverslip</td>
			<td style="width:252px;">Menzel-Glaser, Germany</td>
			<td style="width:189px;">BB024040SC</td>
			<td>24 mm &#215; 40 mm, #5</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Plasma generator instrument</td>
			<td style="width:252px;">Diener</td>
			<td style="width:189px;">Zepto B</td>
			<td>Frequency: 40 kHz and plasma generator power: 0-30 W</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">PTFE tubing</td>
			<td style="width:252px;">PKM SA, Switzerland</td>
			<td style="width:189px;">AWG-TFS-XXX</td>
			<td style="width:371px;">AWG 20TFS, roll of 100 m</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">neMESYS Syringe Pumps</td>
			<td style="width:252px;">Cetoni GmbH, Germany</td>
			<td style="width:189px;">Low Pressure (290N)</td>
			<td>-</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Disposable Cup</td>
			<td style="width:252px;">Semadeni, Switzerland</td>
			<td style="width:189px;">8323</td>
			<td>PS, 200 ml</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Plastic Spatula</td>
			<td style="width:252px;">Semadeni, Switzerland</td>
			<td style="width:189px;">3340</td>
			<td>L &#215; W : 135 mm x 14 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Disposable Scalpels</td>
			<td style="width:252px;">B. Braun, Switzerland</td>
			<td style="width:189px;">233-5320</td>
			<td>Nr. 20</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Disposable Syringes</td>
			<td style="width:252px;">VWR, Switzerland</td>
			<td style="width:189px;">613-3951</td>
			<td>5 ml, Discardit II</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Acetic Acid</td>
			<td style="width:252px;">Sigma-Aldrich, Switzerland</td>
			<td style="width:189px;">695092-500</td>
			<td>&#62;=99.7%, CAUTION: Handle it only under fume hood.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">1,3,5-benzenetricarbaldehyde</td>
			<td style="width:252px;">Aldrich-Fine Chemicals</td>
			<td style="width:189px;">753491</td>
			<td>97%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">1,3,5-Tris(4-aminophenyl)benzene</td>
			<td style="width:252px;">Tokyo Chemical Industry</td>
			<td style="width:189px;">T2728-5G</td>
			<td>&#62;93.0%</td>
		</tr>
	</tbody>
</table>

microfluidic-based synthesis of covalent organic frameworks (cofs): a tool for continuous production of cof fibers and direct printing on a surface

共价有机骨架（COFs）是一类多孔共价材料，经常被合成为不可加工的结晶粉末。 2005年第一次报告了COF，其重点是建立新的合成路线进行准备。迄今为止，用于COF合成的大多数可用的合成方法是基于在溶剂热条件下的体积混合。因此，越来越多的兴趣开发COF合成的系统方案，提供对反应条件的精细控制，并提高表面上的COF加工性，这对于在实际应用中的应用至关重要。在本文中，我们提出了一种新型的基于微流体的COF合成方法，其中两个构成结构单元1,3,5-苯三甲醛（BTCA）和1,3,5-三（4-氨基苯基）苯（TAPB）之间的反应，在受控扩散条件下和室温下进行。使用这种方法会产生海绵样的哭泣COF材料的高分子纤维，以下称为MF-COF。 MF-COF的机械性能和该方法的动态特性允许连续生产MF-COF纤维并直接印刷在表面上。一般方法开辟了新的潜在应用，需要在柔性或刚性表面上高级打印2D或3D COF结构。

在我们的研究中使用的微流体装置是使用传统的PDMS复制模制20制造的，并且包括合并到主微通道中的四个微流体入口通道。最终的微流体装置由结构化PDMS层和用于封闭印迹微通道的玻璃盖玻片组成， 如图1B所示。 <img alt="图1" class="xfigimg" src="/files/ftp_upload/56020/56020fig1.jpg" /> 图1:分子构建块和单层微流体装置。 （ A ）TAPB和BTCA的化学结构。 （ B ）用于合成COF纤维的微流体装置的照片。 <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56020/56020fig1large.jpg" target="_blank">请点击这里查看更大的版本</a>数字。 四个入口微流体通道的高度为50μm，宽度为50μm，并汇聚成一个主要的微流体通道，高达50μm，宽度为250μm。将两种试剂流（乙酸中的BTCA和TAPB）注入两个中间输入通道，将两个纯乙酸鞘流引入侧通道（ 图2 ，合成区）。所有四个流汇集在主要微流体通道中，其中反应在扩散控制下进行。在这项工作中，所有四个输入流量都调整到100μL/ min的流速。一方面，这种条件确保连续的MF-COF纤维的形成（干燥的MF-COF纤维的生产速率约为 2mg / min），另一方面避免了主要微流体通道的阻塞以及位于微流体装置的出口处的管。这样优化的流程c可以生产具有适当机械性能的连续黄色MF-COF纤维，用于在表面上直接印刷（ 图2 ，印刷区域）。 <img alt="图2" class="xfigimg" src="/files/ftp_upload/56020/56020fig2.jpg" /> 图2:用于合成MF-COF纤维的微流体装置的示意图。指出合成和印刷区。 <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56020/56020fig2large.jpg" target="_blank">请点击此处查看此图的较大版本。</a> 我们以前的研究6提供了详细的化学特征研究以及合成的MF-COF纤维的热稳定性分析。 图3显示衰减的全反射率FT-IR（ATR-FT-IR）数据<html>单体TAPB和BTCA的粉末X射线衍射（PXRD）图案以及MF-COF纤维。 ATR-FT-IR测量显示MF-COF纤维中NH拉伸带（3,300-3,500cm -1 ）的消失和位于1,689cm -1处的新带的出现，其对应于亚胺键形成。此外，MF-COF纤维的PXRD数据与模拟图案相比较。有趣的是，MF-COF的形态学表征显示，MF-COF与RT-COF-1（在本体条件下合成）不同，MF-COF由形成3D海绵状多孔组织的相互连接的微米和纳米纤维组成，而RT-COF-1形成不含界定微结构的薄膜17 。这种形态差异也解释了MF-COF中N 2吸附显着增加，如Brunauer-Emmet-Teller（BET）分析测定的总比表面积所证明的那样。 _content"fo:keep-together.within-page ="1"&gt; <img alt="图3" class="xfigimg" src="/files/ftp_upload/56020/56020fig3.jpg" /> 图3:试剂和MF-COF纤维的化学和结构分析。 （ A ）单体TAPB和BTCA以及MF-COF纤维的ATR-FT-IR光谱。 （ B ）MF-COF纤维（具有模拟图案）和TAPB和BTCA的PXRD图案。 <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56020/56020fig3large.jpg" target="_blank">请点击此处查看此图的较大版本。</a> 这些结果表明使用微流体反应合成的COF是独特的，并且使用替代的合成方法不能实现MF-COF特征和性能。从MF-COF的微观组织得到的机械性能允许MF-COF纤维在表面上的共形印刷。 图4 </strong&gt;示出了使用基于微流体的合成方法印刷在玻璃表面上的不同的2D和3D MF-COF结构。 <img alt="图4" class="xfigimg" src="/files/ftp_upload/56020/56020fig4.jpg" /> 图4:玻璃表面上的2D和3D MF-COF结构。 （ A ）写作实验（用"ETH"和"3D COF"）的照片以及（ B ）二维和（ C ）三维MF-COF结构在玻璃上的印刷实验。比例尺= 1厘米。 <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56020/56020fig4large.jpg" target="_blank">请点击此处查看此图的较大版本。</a> 此外，合成的MF-COF纤维的机械性能以及打印方法的简单性和灵活性允许Con在不同柔性和刚性基材上缠绕MF-COF沉积。 如图5所示 ，MF-COF可以印刷到诸如玻璃，薄纸，纸板，铝箔和聚苯乙烯的各种表面上。 <img alt="图5" class="xfigimg" src="/files/ftp_upload/56020/56020fig5.jpg" /> 图5:MF-COF纤维在不同基材上的印刷。 （ A ）玻璃，（ B ）薄纸，（ C ）纸板，（ D ）铝箔和（ E ）聚苯乙烯表面上的MF-COF的照片。所有比例尺为1厘米。 <a href="https://ecsource-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56020/56020fig5large.jpg" target="_blank">请点击此处查看此图的较大版本。</a>

Watch this Scientific Journal Video about Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface at JoVE.com

Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

我们提出一种新型的基于微流体的合成共价有机骨架（COFs）的方法。我们展示了如何使用这种方法来生产连续的COF纤维，以及表面上的2D或3D COF结构。

基于微流体的共价有机骨架（COFs）的合成:用于连续生产COF纤维和直接印刷在表面上的工具

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The ...

microfluidic-based-synthesis-covalent-organic-frameworks-cofs-tool

Nanyang Technological University

Research

JoVE Journal

Chemistry

Microfluidic-based Synthesis of Covalent Organic Frameworks (COFs): A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

13.2K 次观看.  ETH Zurich. 我们提出一种新型的基于微流体的合成共价有机骨架（COFs）的方法。我们展示了如何使用这种方法来生产连续的COF纤维，以及表面上的2D或3D COF结构。 

视频: Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

Preparation and Use of Samarium Diiodide (SmI2) in Organic Synthesis: The Mechanistic Role of HMPA and Ni(II) Salts in the Samarium Barbier Reaction

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of molecular iodine to samarium metal in THF.1,2-3 It is a mild and selective single electron reductant and its versatility is a result of its ability to initiate a wide range of reductions including C-C bond-forming and cascade or sequential reactions. SmI2 can reduce a variety of functional groups including sulfoxides and sulfones, phosphine oxides, epoxides, alkyl and aryl halides, carbonyls, and conjugated double bonds.2-12 One of the fascinating features of SmI-2-mediated reactions is the ability to manipulate the outcome of reactions through the selective use of cosolvents or additives. In most instances, additives are essential in controlling the rate of reduction and the chemo- or stereoselectivity of reactions.13-14 Additives commonly utilized to fine tune the reactivity of SmI2 can be classified into three major groups: (1) Lewis bases (HMPA, other electron-donor ligands, chelating ethers, etc.), (2) proton sources (alcohols, water etc.), and (3) inorganic additives (Ni(acac)2, FeCl3, etc).3
Understanding the mechanism of SmI2 reactions and the role of the additives enables utilization of the full potential of the reagent in organic synthesis. The Sm-Barbier reaction is chosen to illustrate the synthetic importance and mechanistic role of two common additives: HMPA and Ni(II) in this reaction. The Sm-Barbier reaction is similar to the traditional Grignard reaction with the only difference being that the alkyl halide, carbonyl, and Sm reductant are mixed simultaneously in one pot.1,15 Examples of Sm-mediated Barbier reactions with a range of coupling partners have been reported,1,3,7,10,12 and have been utilized in key steps of the synthesis of large natural products.16,17 Previous studies on the effect of additives on SmI2 reactions have shown that HMPA enhances the reduction potential of SmI2 by coordinating to the samarium metal center, producing a more powerful,13-14,18 sterically encumbered reductant19-21 and in some cases playing an integral role in post electron-transfer steps facilitating subsequent bond-forming events.22 In the Sm-Barbier reaction, HMPA has been shown to additionally activate the alkyl halide by forming a complex in a pre-equilibrium step.23
Ni(II) salts are a catalytic additive used frequently in Sm-mediated transformations.24-27 Though critical for success, the mechanistic role of Ni(II) was not known in these reactions. Recently it has been shown that SmI2 reduces Ni(II) to Ni(0), and the reaction is then carried out through organometallic Ni(0) chemistry.28
These mechanistic studies highlight that although the same Barbier product is obtained, the use of different additives in the SmI2 reaction drastically alters the mechanistic pathway of the reaction. The protocol for running these SmI2-initiated reactions is described.

Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction

A straightforward procedure for the preparation of samarium diiodide (SmI2) in THF is described. The role of two main additives namely hexamethylphosphoramide (HMPA) and Ni(acac)2 in Sm mediated reactions is demonstrated in the Sm-Barbier reaction.

二碘化钐的制备和使用（SMI<sub&gt; 2</sub&gt;）在有机合成中:HMPA和镍（II）盐的钐巴尔比耶反应的机理作用

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of ...

科研

化学

Covalent Binding of BMP-2 on Surfaces Using a Self-assembled Monolayer Approach

Bone morphogenetic protein 2 (BMP-2) is a growth factor embedded in the extracellular matrix of bone tissue. BMP-2 acts as trigger of mesenchymal cell differentiation into osteoblasts, thus stimulating healing and de novo bone formation. The clinical use of recombinant human BMP-2 (rhBMP-2) in conjunction with scaffolds has raised recent controversies, based on the mode of presentation and the amount to be delivered. The protocol presented here provides a simple and efficient way to deliver BMP-2 for in vitro studies on cells. We describe how to form a self-assembled monolayer consisting of a heterobifunctional linker, and show the subsequent binding step to obtain covalent immobilization of rhBMP-2. With this approach it is possible to achieve a sustained presentation of BMP-2 while maintaining the biological activity of the protein. In fact, the surface immobilization of BMP-2 allows targeted investigations by preventing unspecific adsorption, while reducing the amount of growth factor and, most notably, hindering uncontrolled release from the surface. Both short- and long-term signaling events triggered by BMP-2 are taking place when cells are exposed to surfaces presenting covalently immobilized rhBMP-2, making this approach suitable for in vitro studies on cell responses to BMP-2 stimulation.

We describe a method for accomplishing efficient immobilization of BMP-2 on surfaces. Our approach is based on the formation of a self-assembled monolayer to achieve the covalent binding of BMP-2 via its free amine residues. This method is a useful tool to study signaling at the cell membrane.

BMP-2的共价结合利用表面上的自组装单层膜法

Bone morphogenetic protein 2 (BMP-2) is a growth factor embedded in the extracellular matrix of bone tissue. BMP-2 acts as trigger of mesenchymal cell ...

Thin-layer Chromatographic (TLC) Separations and Bioassays of Plant Extracts to Identify Antimicrobial Compounds

A common screen for plant antimicrobial compounds consists of separating plant extracts by paper or thin-layer chromatography (PC or TLC), exposing the chromatograms to microbial suspensions (e.g. fungi or bacteria in broth or agar), allowing time for the microbes to grow in a humid environment, and visualizing zones with no microbial growth.&#160;The effectiveness of this screening method, known as bioautography, depends on both the quality of the chromatographic separation and the care taken with microbial culture conditions.&#160;This paper describes standard protocols for TLC and contact bioautography&#160;with a novel application to amino acid-fermenting bacteria. The extract is separated on flexible (aluminum-backed) silica TLC plates, and bands are visualized under ultraviolet (UV) light.&#160;Zones are cut out and incubated face down onto agar inoculated with the test microorganism.&#160;Inhibitory bands are visualized by staining the agar plates with tetrazolium red.&#160;The method is applied to the separation of red clover (Trifolium pratense cv. Kenland) phenolic compounds and their screening for activity against Clostridium sticklandii, a hyper ammonia-producing bacterium (HAB) that is native to the bovine rumen.&#160;The TLC methods apply to many types of plant extracts&#160;and other bacterial species (aerobic or anaerobic), as well as fungi, can be used as test organisms if culture conditions are modified to fit the growth requirements of the species.

Thin-layer Chromatographic TLC Separations and Bioassays of Plant Extracts to Identify Antimicrobial Compounds

Methods are described for thin-layer chromatographic (TLC) separation of plant extracts and contact bioautography to identify antibacterial metabolites. The methods are applied to the screening of red clover phenolic compounds inhibiting hyper&#160;ammonia-producing bacteria (HAB) native to the bovine rumen.

薄层色谱（TLC）分离和植物提取物的生物测定识别抗菌化合物

A common screen for plant antimicrobial compounds consists of separating plant extracts by paper or thin-layer chromatography (PC or TLC), exposing the ...

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

功能化的合成与表征金属 - 有机骨架

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

超分子胶体的合成与表征

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Synthesis of a Water-soluble Metal&#8211;Organic Complex Array

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as Ru(II), Pt(II), and Rh(III). The compound, named as a water-soluble metal-organic complex array (WSMOCA), is obtained through 1) the conventional solution-chemistry-based preparation of the corresponding metal complex monomers having a 9-fluorenylmethyloxycarbonyl (Fmoc)-protected amino acid moiety and 2) their sequential coupling together with other water-soluble organic building units on the surface-functionalized polymeric resin by following the procedures originally developed for the solid-phase synthesis of polypeptides, with proper modifications. Traces of reactions determined by mass spectrometric analysis at the representative coupling steps in stage 2 confirm the selective construction of a predetermined sequence of metal centers along with the peptide backbone. The WSMOCA cleaved from the resin at the end of stage 2 has a certain level of solubility in aqueous media dependent on the pH value and/or salt content, which is useful for the purification of the compound.

A potential general method for the synthesis of water-soluble multimetallic peptidic arrays containing a predetermined sequence of metal centers is presented.

一个水溶性金属 - 有机络合物阵列合成

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as ...

A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various precursor noble metal ions with reducing agents in a 1:1 (v/v) ratio results in the formation of metal gels within seconds to minutes compared to much longer synthesis times for other techniques such as sol-gel. Conducting the reduction step in a microcentrifuge tube or small volume conical tube facilitates a proposed nucleation, growth, densification, fusion, equilibration model for gel formation, with final gel geometry smaller than the initial reaction volume. This method takes advantage of the vigorous hydrogen gas evolution as a by-product of the reduction step, and as a consequence of reagent concentrations. The solvent accessible specific surface area is determined with both electrochemical impedance spectroscopy and cyclic voltammetry. After rinsing and freeze drying, the resulting aerogel structure is examined with scanning electron microscopy, X-ray diffractometry, and nitrogen gas adsorption. The synthesis method and characterization techniques result in a close correspondence of aerogel ligament sizes. This synthesis method for noble metal aerogels demonstrates that high specific surface area monoliths may be achieved with a rapid and direct reduction approach.

A rapid, direct solution-based reduction synthesis method to obtain Au, Pd, and Pt aerogels is presented.

直接溶液还原法快速合成金、钯、铂气凝胶的研究

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various ...

Surface Functionalization of Metal-Organic Frameworks for Improved Moisture Resistance

Metal-organic frameworks (MOFs) are a class of porous inorganic materials with promising properties in gas storage and separation, catalysis and sensing. However, the main issue limiting their applicability is their poor stability in humid conditions. The common methods to overcome this problem involve the formation of strong metal-linker bonds by using highly charged metals, which is limited to a number of structures, the introduction of alkylic groups to the framework by post-synthetic modification (PSM) or chemical vapour deposition (CVD) to enhance overall hydrophobicity of the framework. These last two usually provoke a drastic reduction of the porosity of the material. These strategies do not permit to exploit the properties of the MOF already available and it is imperative to find new methods to enhance the stability of MOFs in water while keeping their properties intact. Herein, we report a novel method to enhance the water stability of MOF crystals featuring Cu2(O2C)4&#160;paddle-wheel units, such as HKUST (where HKUST stands for Hong Kong University of Science &#38; Technology), with the catechols functionalized with alkyl and fluoro-alkyl chains. By taking advantage of the unsaturated metal sites and the catalytic catecholase-like activity of CuII ions, we are able to create robust hydrophobic coatings through the oxidation and subsequent polymerization of the catechol units on the surface of the crystals under anaerobic and water-free conditions without disrupting the underlying structure of the framework. This approach not only affords the material with improved water stability but also provides control over the function of the protective coating, which enables the development of functional coatings for the adsorption and separations of volatile organic compounds. We are confident that this approach could also be extended to other unstable MOFs featuring open metal sites.

Robust functional catechol coatings were produced in one step by direct reaction of the material known as HKUST with synthetic catechols under anaerobic conditions. The formation of homogeneous coatings surrounding the entire crystal is ascribed to the biomimetic catalytic activity of Cu(II) dimers on the external surface of the crystals.

金属-有机框架的表面功能化改善防潮性能

Metal-organic frameworks (MOFs) are a class of porous inorganic materials with promising properties in gas storage and separation, catalysis and sensing. ...

Mass Spectrometry-Guided Genome Mining as a Tool to Uncover Novel Natural Products

The chemical space covered by natural products is immense and widely unrecognized. Therefore, convenient methodologies to perform wide-ranging evaluation of their functions in nature and potential human benefits (e.g., for drug discovery applications) are desired. This protocol describes the combination of genome mining (GM) and molecular networking (MN), two contemporary approaches that match gene cluster-encoded annotations in whole genome sequencing with chemical structure signatures from crude metabolic extracts. This is the first step towards the discovery of new natural entities. These concepts, when applied together, are defined here as MS-guided genome mining. In this method, the main components are previously designated (using MN), and structurally related new candidates are associated with genome sequence annotations (using GM). Combining GM and MN is a profitable strategy to target new molecule backbones or harvest metabolic profiles in order to identify analogues from already known compounds.

A mass spectrometry-guided genome mining protocol is established and described here. It is based on genome sequence information and LC-MS/MS analysis and aims to facilitate identification of molecules from complex microbial and plant extracts.

质谱导览基因组挖掘作为发现新天然产品的工具

The chemical space covered by natural products is immense and widely unrecognized. Therefore, convenient methodologies to perform wide-ranging evaluation ...

Synthesis of Single-Crystalline Core-Shell Metal-Organic Frameworks

Because of their designability and unprecedented synergistic effects, core-shell metal-organic frameworks (MOFs) have been actively examined recently. However, the synthesis of single-crystalline core-shell MOFs is very challenging, and thus a limited number of examples have been reported. Here, we suggest a method of synthesizing single-crystalline HKUST-1@MOF-5 core-shells, which is HKUST-1 at the center of MOF-5. Through the computational algorithm, this pair of MOFs was predicted to have the matched lattice parameters and chemical connection points at the interface. To construct the core-shell structure, we prepared the octahedral- and cubic-shaped HKUST-1 crystals as a core MOF, in which the (111) and (001) facets were mainly exposed, respectively. Via the sequential reaction, the MOF-5 shell was well-grown on the exposed surface, showing a seamless connect interface, which resulted in the successful synthesis of single-crystalline HKUST-1@MOF-5. Their pure phase formation was proved by optical microscopic images and powder X-ray diffraction (PXRD) patterns. This method presents the potential of and insights into the single-crystalline core-shell synthesis with different kinds of MOFs.

Here, we demonstrate a protocol for the two-step synthesis of single-crystalline core-shells using a non-isostructural metal-organic framework (MOF) pair, HKUST-1 and MOF-5, which have well-matched crystal lattices.

单晶核壳金属有机骨架的合成

Because of their designability and unprecedented synergistic effects, core-shell metal-organic frameworks (MOFs) have been actively examined recently. ...