Zeolites with Continuously Tuneable Porosity

Abstract

Zeolites are important materials whose utility in industry depends on the nature of their porous structure. Control over microporosity is therefore a vitally important target. Unfortunately, traditional methods for controlling porosity, in particular the use of organic structure-directing agents, are relatively coarse and provide almost no opportunity to tune the porosity as required. Here we show how zeolites with a continuously tuneable surface area and micropore volume over a wide range can be prepared. This means that a particular surface area or micropore volume can be precisely tuned. The range of porosity we can target covers the whole range of useful zeolite porosity: from small pores consisting of 8-rings all the way to extra-large pores consisting of 14-rings.

In situ solid-state NMR and XRD studies of the ADOR process and the unusual structure of zeolite IPC-6

“…In higher acidity conditions there is, however, a significant change in the chemistry of the system. In situ MAS NMR 29 Si spectra show the same fast production of Q 3 sites on hydrolysis, followed by a significant relative increase in the intensity of the Q 4 (Si(OSi) 4 ) resonances over longer time periods (Figure 1b). This change in intensity is consistent with a rearrangement, such that the layers become reconnected by silica species.…”

“…This adds further evidence that the layers are tied together by the silica species after the rearrangement process is complete, as shown in Figure 3c. The only change between IPC-2P and IPC-2 is the completion of the condensation process, so that all (or at least the vast majority) of the silicon atoms end up as Q 4 (Figure 3b). It is interesting to note that the rearrangement process described above leads to scrambling of the oxygen atoms, as can be shown using isotopically-enriched H 2 17 O for the disassembly hydrolysis, as both Si-O-Si and Si-OH oxygens are enriched as shown by 17 O MAS NMR spectra collected at 20.0 T (See supplementary information, Figure 1).…”

“…1,4 The process comprises four distinct steps. The assembly (A) process involves the preparation of a parent zeolite with suitable chemical and topological properties for…”

“…3 One consequence of the organisation step is the possibility of using different structural units to link the layers to form the different zeolites, leading to isoreticular families. 1,4 Controlling these linkages offers an important tool by which the final structures can be precisely tuned, and leads to, amongst other things, the possibility of continuously tuneable porosity. 4 The isoreticular family of structures discussed in this manuscript are IPC-4, IPC-2 and IPC-6, which contain the same UTL layer types linked by oxygen atoms (which we call PCR linkages, as they are present in the PCR zeolite topology), single four ring units (called OKO linkages) and 50%/50% PCR/OKO linkages respectively.…”

“…1,4 Controlling these linkages offers an important tool by which the final structures can be precisely tuned, and leads to, amongst other things, the possibility of continuously tuneable porosity. 4 The isoreticular family of structures discussed in this manuscript are IPC-4, IPC-2 and IPC-6, which contain the same UTL layer types linked by oxygen atoms (which we call PCR linkages, as they are present in the PCR zeolite topology), single four ring units (called OKO linkages) and 50%/50% PCR/OKO linkages respectively. 4 Here we report in situ magic angle spinning (MAS) solid-state NMR and XRD mechanistic studies on the evolution of the disassembly, organisation and reassembly steps in order to fully understand how these different interlayer linkages develop over the course of the reaction under the relevant conditions.…”