Center for Surface Chemistry and Catalysis, KU Leuven, 3001 Heverlee, Belgium.
Nat Mater. 2012 Dec;11(12):1059-64. doi: 10.1038/nmat3455. Epub 2012 Oct 21.
Although the search for new zeolites has traditionally been based on trial and error, more rational methods are now available. The theoretical concept of inverse σ transformation of a zeolite framework to generate a new structure by removal of a layer of framework atoms and contraction has for the first time been achieved experimentally. The reactivity of framework germanium atoms in strong mineral acid was exploited to selectively remove germanium-containing four-ring units from an UTL type germanosilicate zeolite. Annealing of the leached framework through calcination led to the new all-silica COK-14 zeolite with intersecting 12- and 10-membered ring channel systems. An intermediate stage of this inverse σ transformation with dislodged germanate four-rings still residing in the pores could be demonstrated. Inverse σ transformation involving elimination of germanium-containing structural units opens perspectives for the synthesis of many more zeolites.
虽然新型沸石的寻找传统上依赖于反复试验，但现在有了更合理的方法。沸石骨架的反σ变换理论概念，通过去除一层骨架原子和收缩来生成新结构，首次在实验中得到实现。利用框架锗原子在强矿物酸中的反应性，从 UTL 型锗硅酸盐沸石中选择性地去除含锗的四环单元。通过煅烧对浸出的骨架进行退火，导致具有相交的 12-和 10-元环通道系统的新型全硅 COK-14 沸石的形成。可以证明这种反σ变换的中间阶段，带脱位的锗酸盐四环仍然驻留在孔中。涉及消除含锗结构单元的反σ变换为合成更多沸石开辟了前景。
