We report computational study of the distribution of germanium ions among the double four-membered rings (D4Rs) in SCM-14 germanosilicate and the influence of the structure-directing agent (SDA) on the stability...

Structural flexibility is an intrinsic feature of zeolites, and the characterization of such dynamic behavior is key to maximizing their performance and realizing their potential in both existing and emerging applications. Here, the flexibility of a high-aluminum nano-sized RHO zeolite is directly visualized with in situ TEM for the first time. Variable temperature experiments directly observe the physical expansion of the discrete nanocrystals in response to changes in both guest-molecule chemistry (Ar vs CO2) and temperature. The observations are complemented by operando FTIR spectroscopy verifying the nature of the adsorbed CO2 within the pore network, the desorption kinetics of carbonate species, and changes to the structural bands at high temperatures. Quantum chemical modeling of the RHO zeolite structure substantiates the effect of cation (Na+ and Cs+) mobility in the absence and presence of CO2 on the flexibility behavior of the structure. The results demonstrate the combined influences of temperature and CO2 on the structural flexibility consistent with the experimental microscopy observations.

We report the formation of a new Lewis acid Al site in H-FAU zeolite upon 650 ⁰C thermal treatment, unknown for any zeolite. Spectroscopy and DFT calculations reveal this site is a naked Al+3 ion which is charge balanced by a triplet of adjacent framework oxygens with net charge of -1 for each Si-O-Al moiety. This is the first reported observation of a +3 cation stabilized in a zeolite and the first confirmation of existence of aluminum triplets (as opposed to Al pairs) in that can stabilize such cations in siliceous zeolites. This site forms a thermally stable carbonyl O3Al-CO complex with the highest known frequency at 2252 cm-1 for a carbonyl complex on any solid material. These findings open new horizons in zeolite chemistry and expand our understanding of polyvalent metals’ interactions with zeolites.