Owing to their large surface area and high uptake capacity, metal–organic frameworks (MOFs) have attracted considerable attention as potential materials for gas storage, energy conversion, and electrocatalysis. Various strategies have recently been proposed to manipulate the MOF surface chemistry to facilitate exposure of the embedded metal centers at the crystal surface to allow more effective binding of target molecules to these active sites. Nevertheless, such strategies remain complex, often requiring strict control over the synthesis conditions to avoid blocking pore access, reduction in crystal quality, or even collapse of the entire crystal structure. In this work, we exploit the hydrodynamics and capillary resonance associated with acoustically-driven dynamically spreading and nebulizing thin films as a new method for ultrafast synthesis of swordlike Cu₃(1,3,5-benzenetricarboxylate)_n (Cu–BTC) MOFs with unique monoclinic crystal structures (P2₁/n) distinct to that obtained via conventional bulk solvothermal synthesis, with ‘swordlike’ morphologies whose lengths far exceed their thicknesses. Through pulse modulation and taking advantage of the rapid solvent evaporation associated with the high nebulisation rates, we are also able to control the thicknesses of these large aspect ratio (width and length with respect to the thickness) crystals by arresting their vertical growth, which, in turn, allows exposure of the metal active sites at the crystal surface. An upshot of such active site exposure on the crystal surface is the concomitant enhancement in the conductivity of the MOF, evident from the improvement in its current density by two orders of magnitude.

中文翻译：

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具有暴露的活性金属位点的剑状Cu3（1,3,5-苯三甲酸）n金属-有机骨架晶体的超快组装。

由于金属-有机骨架（MOF）的表面积大和吸收能力强，作为潜在的气体存储，能量转换和电催化材料受到了广泛的关注。最近已经提出了各种策略来操纵MOF表面化学，以促进晶体表面上嵌入的金属中心的暴露，以使靶分子与这些活性位点更有效地结合。然而，这样的策略仍然很复杂，经常需要严格控制合成条件，以避免阻塞孔的进入，晶体质量的降低甚至整个晶体结构的崩溃。在这项工作中₃（1,3,5-苯三甲酸） _n（Cu–BTC） _n MOF具有独特的单斜晶体结构（ P 2 ₁ / n）与通过传统的本体溶剂热合成，具有“剑状”形态，其长度远远超过其厚度。通过脉冲调制并利用与高雾化速率相关的快速溶剂蒸发，我们还能够通过阻止其垂直生长来控制这些大长宽比（厚度和长度相对于厚度）的厚度，继而，允许金属活性位点暴露在晶体表面。晶体表面上这种活性部位暴露的结果是伴随着MOF电导率的提高，这可以从其电流密度提高两个数量级中看出。