Maheshwari Sudeep, Jordan Edgar, Kumar Sandeep, Bates Frank S, Penn R Lee, Shantz Daniel F, Tsapatsis Michael
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
J Am Chem Soc. 2008 Jan 30;130(4):1507-16. doi: 10.1021/ja077711i. Epub 2008 Jan 8.
MCM-22(P), the precursor to zeolite MCM-22, consists of stacks of layers that can be swollen and exfoliated to produce catalytically active materials. However, the current swelling procedures result in significant degradation of crystal morphology along with partial loss of crystallinity and dissolution of the crystalline phase. Fabrication of polymer nanocomposites and coatings with MCM-22 for separation, barrier, and other applications requires a swelling method that does not alter drastically the crystal morphology and layer structure and preserves the high aspect ratio of the layers. Here, we demonstrate such a method by swelling MCM-22(P) at room temperature. The low-temperature process does not disrupt the framework connectivity present in the parent MCM-22(P) material. By extensive washing with water, the swollen material, MCM-22(PS-RT), evolves to a new ordered layered structure. Interestingly, the swelling procedure is reversible and the swollen material can be restored back to MCM-22(P) by acidification of the sample. The swollen material can also be pillared to produce an MCM-36 analogue. It can also be exfoliated, and layers can be incorporated in a polymer matrix to make nanocomposites.
MCM-22(P)是沸石MCM-22的前体，由可膨胀和剥离以产生催化活性材料的层堆叠组成。然而，当前的膨胀程序会导致晶体形态显著降解，同时结晶度部分丧失且晶相溶解。用MCM-22制备用于分离、阻隔及其他应用的聚合物纳米复合材料和涂层需要一种不会大幅改变晶体形态和层结构且能保持层的高纵横比的膨胀方法。在此，我们通过在室温下使MCM-22(P)膨胀来展示这样一种方法。低温过程不会破坏母体MCM-22(P)材料中存在的骨架连通性。通过用水大量洗涤，膨胀后的材料MCM-22(PS-RT)演变成一种新的有序层状结构。有趣的是，膨胀过程是可逆的，通过对样品进行酸化，膨胀后的材料可以恢复为MCM-22(P)。膨胀后的材料还可以被柱撑以制备MCM-36类似物。它也可以被剥离，并且层可以被掺入聚合物基质中以制备纳米复合材料。
