Repurposing Templates for Zeolite Synthesis from Simulations and Data Mining

Abstract

Zeolites span a large variety of microporous crystal structures, making them useful materials for catalysis and separations. However, controlling phase competition in their synthesis often requires organic structure-directing agents (OSDAs) to selectively crystallize the desired topologies. Whereas computational design of OSDAs can help in selecting adequate candidates for zeolite synthesis, machine-generated templates are often complex or expensive. In this work, we use shape and binding metrics to propose templates for over 100 zeolites and to rationalize dual-OSDA approaches. Starting from OSDAs from the literature, promising templates were selected for zeolites ranging from clathrasil frameworks to extra large-pore structures. Selectivity maps derived from phase competition metrics show that small- and medium-pore zeolites tend to be more shape-selective toward their templates than their large-pore counterparts. Finally, shape and volume descriptors allow identification of OSDAs that may act as synergistic pore-fillers for different cavities of zeolites. The application of this theory is demonstrated for the case of the KFI zeolite, which may be synthesized using tetraethylammonium and OSDAs repurposed from high-silica LTA synthesis as dual OSDAs. This work may help in the discovery of new synthesis routes for known zeolites using shape descriptors and repurposed OSDAs.

Competition between Mononuclear and Binuclear Copper Sites across Different Zeolite Topologies

“…Only certain zeolite types, such as CHA synthesized with specific protocols, evidence a pseudorandom aluminum distribution, , whereas zeolites such as commercial MOR commonly show nonrandom Al distributions. − The organic structure directing agents (SDAs), inorganic cations present in the synthesis media, and synthesis conditions (temperature and time) largely determine the Al distribution. ,,, Although quantifying the populations of specific 2Al configurations remains a challenge, techniques such as Co 2+ titration, , high-field 27 Al NMR, , and a combination of X-ray absorption and NMR give information on macroscopic Al distributions. For nonrandom (biased) Al distributions, Cu speciation may change significantly due to changes in the populations of 2Al sites that have the most favorable exchange free energies.…”

Biomass carbon mining to develop nature-inspired materials for a circular economy

“…Moreover, the use of data mining and generative neural networks like those applied in zeolites could be potentially useful to design porous hydrochars in the future. 232 …”

The Directing Role of Aluminum in the Synthesis of PST-21 (PWO), PST-22 (PWW), and ERS-7 (ESV) Zeolites

“…Using the information from the publications of these three zeolites, the OSDAs employed for the syntheses were identified, and a list of four OSDAs was obtained. To determine the competing zeolite phases for each OSDA molecule, an exhaustive literature search using the Organic Structure Database (OSDB) 44 was performed, which led to 52 publications. Similar to our previous work, 40 the publications that include (i) synthesis in the presence of seed crystals, (ii) synthesis in the presence of inorganic cations, (iii) synthesis of germanosilicates, and (iv) synthesis of MFI, FAU, and MOR phases, since they are easy to obtain without an SDA present, were removed from the records to focus on the structuredirecting effect of Al and F − .…”