On the Sn(II) and Sn(IV) incorporation into the AFI-structured AlPO4-based framework: the first significantly acidic SnAPO-5

Abstract

Both Sn(II) and Sn(IV) chlorides were tested as sources for tin incorporation into an AlPO 4 -5 framework. N-Methyldicyclohexylamine (MCHA) was chosen as a structure-directing agent, taking advantage of its reported high specificity towards AFI-structured AlPO 4 -based materials. Pure AFI materials were successfully produced, irrespective of the Sn source in a wide range of gel compositions. Whereas the different characterization techniques of the Sn(IV)APO-5 materials certify the unfavourable (or at least low-quality) incorporation of Sn, as expected from previous studies, there is no doubt about the right Sn(II) incorporation into the AlPO 4 framework. The amount of Sn(II) able to be properly incorporated into the AlPO 4 -5 structure is significantly higher than that described in the literature for Sn(IV)APO-5 materials as well as for the Sn(IV)APO-5 materials prepared in this work. For the first time, AlPO 4 -based microporous catalysts were tested in the Friedel-Crafts acylation of anisole. Supporting the characterization results, Sn(IV)APO-5 and especially Sn(II)APO-5 were active catalysts in such reactions which require acid centers to take place. Since all tested AlPO 4 -based materials (pure AlPO 4 -5, SAPO-5 and SnAPO-5) possess an AFI structure and similar surfaces areas, the extent of the acylation of anisole was taken as indirect proof of acidic strength. The conversion given by pure AlPO 4 -5 was negligible in comparison with Sn(II)APO-5, which overcomes the activity of the SAPO-5 and even that of a standard zeolite H-beta.

Synthesis and characterization of a new Cd-based metal-organic framework isostructural with MOF-74/CPO-27 materials

“…The increase of a and b values must be related to the larger size of Cd 2+ , which will presumably lead to a slightly bigger micropore diameter. Although a significant increase in c dimension was also expected, the either low or negligible sensitivity of c to the size of metal ion in isomorphic substitution in other microporous materials with 1-D pore dimensionality and hexagonal space group, has been also found in the literature [34,35] and, more significant, similar behavior has been found between Zn-and Cd-based MOFs with trigonal space group [28,31].…”

Probing ZnAPO-34 Self-Assembly Using Simultaneous Multiple in Situ Techniques

“…In particular, why does the CHA structure form at low temperatures in the presence of 2þ ions, and why does it do so in preference to AFI? 60 Dealing with the latter part first, we observe in Supporting Information Figure S15 (and Table S2) that relaxed TEA cations within the AFI channel pack with a density equal to one template molecule for two adjoining 12-membered rings. Considering that every T-atom in the structure Figure 7.…”

Incorporation of Ti(III) into the AlPO4-5 framework by direct synthesis

“…Indeed, these structural alterations have been taken as support (and even as evidence) that heteroatom incorporation has really occurred. In the case of AlPO 4 -5 structure, unit cell parameter a (and b) was shown to be particularly sensitive to the heteroatom incorporation, whereas c is practically unaffected [35,36]. Figure 2 shows the unit cell parameter a of the structure AFI versus the Ti content of different as-prepared AlPO 4 -5 and Ti(III)APO-5 samples with different Ti content and after being exposed to air for several days.…”

“…Irrespective of the heteroatom nature (Zn [42,43], Mg [43][44][45], Sn(II) [36], etc., and even the paramagnetic Co [46]), these signals are always found at lower field than P(4Al) signal. At high heteroatom content, different almost equidistant signals are detected and attributed to P(4-nAl, nMe) environments [42][43][44]46] (where Me represents the heteroatom ion and n is the integers of Me neighbors to tetrahedral P), even being possible to accurately determine the P/Me ratio in the framework that complements the bulk composition given by chemical analysis techniques [43][44][45].…”