用固体核磁共振研究Al/P>1的磷酸铝分子筛AlPO4-5

用固体高分辩核磁共振（ＮＭＲ）方法对一系列Ａｌ／Ｐ＞１的新型磷酸铝分子筛ＡｌＰＯ４－５中磷和铝的结构状态及联结方式进行了研究，＾２７Ａｌ和＾３１Ｐ ＮＭＲ都给出了在分子筛骨架中存在有Ａｌ－Ｏ－Ａｌ联结方式的实验证据，寓示着在该体系中Ｐ和Ａｌ的排布不再遵循Ｌｏｅｗｅｎｓｔｅｉｎ规则。

Solid-state NMR Studies on AlPO_4-5 Molecular Sieve with Al/P>1

Solid-state NMR spectroscopy was employed to investigate the coordination state of P and Al, as well as their linkages in a series of newly synthesized alunilnophosphate molecular sieve AlPO4-5 with Al/P>1. Both 31P and 27Al NMR provides evidence that Al-O-Al linkages are present in the framework of these molecular sieves, which implies that the ordering arrangement of P and Al does not obey the well-known Loewenstein rule. Apart from the usually observed NMR signals, a broad peak at ca. δ=10 is present in the 27Al MAS spectra of the calcined and dehydrated AlPO4-5 molecular sieves. Due to its large second-order quadrupole shift, an isotropic chemical shift of ca. δ=38 was estimated. Hence, we attribute this signal to 4-coordinated aluminum: AlnAl, (4-n)P )](n=1,2,3,4). Similarly, an additional broad signal at δ=-24 was observed in the corresponding 31P MAS spectra and is due to the P coordination state in which its second coordinated shell contains Al: PnAl, (4-n)P]second shell (n=1,2,3,4).