Synthesis and Applications of Nanoporous Steroidal Crystals

材料的性质在一定程度上取决于其组成分子的性质，但也取决于分子之间的相对排列方式。分子的设计将以特定的、可预测的方式自组织，被称为晶体工程，这是当前科学的主要挑战。具有特殊价值的一种安排是纳米孔组装，其中分子以一种方式聚集在一起，使得通道穿过材料。然后，可以在通道中填充其他分子，以获得具有新特性的杂交物。或者，这些材料可以用作分子筛，允许一些分子通过，但阻止另一些分子。虽然纳米孔结构有用，但本质上很难实现；通常情况下，自然界在形成晶体时更喜欢占据空间。我们最近发现了一类分子，它们不仅具有这种罕见的性质，而且通道也特别宽。不同寻常的是，它们足够大，可以容纳各种各样的客人，例如，包括吸收光线的分子(因此是有色的)。该家族的所有成员都以相同的方式结晶，因此它们的结构应该是可预测的，允许调整性质。我们相信这一发现可以被利用来创造具有各种有用性质的新材料。首先，我们需要确定家庭的大小--我们可以在保持纳米孔排列的情况下，改变结构多少？其次，我们需要研究材料吸收或形成其他分子的能力。这项工作可能表明，我们可以通过仔细调整通道属性来实现困难的分离(包括手性分离)。其他目标包括：(A)通过在分子之间建立键来使材料变得更强。(B)在通道中安排染料分子，以便它们可以共同工作以调节光波。(C)形成混合晶体，其中通道壁的形状可以通过宾客的存在来控制。(D)在通道中沉积金属，形成纳米颗粒或纳米线。如果成功，这项研究可能会在化学加工(分离和催化)、光学技术和纳米技术中得到应用。

The properties of materials depend partly on those of their component molecules, but also on the way the molecules arrange themselves relative to each other. The design of molecules which will self-organise in specific, predictable ways is termed crystal engineering , and is a major challenge for current science. One arrangement of special value is a nanoporous assembly, in which the molecules pack together in such a way as to leave channels running through the material. The channels can then be filled with other molecules, to give hybrids with novel properties. Alternatively, the materials can be used as molecular sieves , allowing some molecules to pass through but blocking others. Although useful, nanoporous structures are intrinsically difficult to achieve; generally, nature prefers to occupy space when forming a crystal. We have recently discovered a family of molecules which not only have this rare property, but for which the channels are also exceptionally wide. Unusually, they are big enough to accept a wide range of guests including, for example, molecules which absorb light (and are therefore coloured). The members of the family all crystallise in the same way, so that their structures should be predictable, allowing tuning of properties.We believe this discovery can be exploited to create new materials with a variety of useful properties. Firstly we need to establish the size of the family - how much can we change the structure and still keep the nanoporous arrangement? Secondly we need to study the materials' abilities to absorb, or form around, other molecules. This work may show that we can achieve difficult separations (including chiral separations) by careful tailoring of channel properties. Other objectives include: (a) Making the materials stronger by creating bonds between the molecules. (b) Arranging dye molecules in the channels, such that they can work together to moderate light waves. (c) Forming mixed crystals, in which the shapes of the channel walls can be controlled by the presence of guests. (d) Depositing metals in the channels, creating nanoparticles or nanowires . If successful the research could have applications in chemical processing (separations and catalysis), optical technology and nanotechnology.