Quantitative Correlations for the Durability of Zeolitic Imidazolate Frameworks in Humid SO2

• Published in: Industrial & engineering chemistry research Vol. 59; no. 1; pp. 245 - 252
• Main Authors: Bhattacharyya, Souryadeep, Sholl, David S, Nair, Sankar
• Format: Journal Article
• Language: English
• Published: American Chemical Society 08.01.2020
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.9b05787

The use of nanoporous zeolitic imidazolate frameworks (ZIFs) - a subclass of metal organic frameworks (MOFs) - in separation processes can be negatively affected by the presence of acid gases such as SO2 or NO x in process streams. The limited experimental data reported on the acid gas stability of these materials is either for dry conditions or under high relative humidity (RH). Partial removal of moisture from process streams may also impart stability to ZIFs toward SO2, and establishing operating boundaries for long-term material utilization is critical. Here we report the first systematic investigation of SO2 degradation of a practically important ZIF (ZIF-8) over a wide RH range from 11 to 95% at ambient temperature (298 K). Bulk stability is probed via crystallinity and porosity measurements, while mechanistic aspects of the degradation process are probed via FTIR and EDX. A simple mathematical correlation involving RH and total SO2 exposure is proposed to quantitatively describe the humid SO2-induced pore volume loss of ZIF-8 under ambient conditions. The potential for generalizing this approach is demonstrated by extending it to another ZIF material (ZIF-14). The use of our predictive correlations toward material durability is illustrated using stability contour plots for these ZIFs materials. This is the first quantitative experimental study of the stability of any MOF across a wide range of acid gas dosage and RH and is a useful step toward more general prediction of the durability of nanoporous materials in humid acid gas streams.