Hierarchical bimetallic metal-organic frameworks with controllable assembling sub-units and interior architectures for enhanced ammonia detection

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 480; p. 147990
• Main Authors: Chowdhury, Silvia, Torad, Nagy L., Godara, Manjeet, El-Amir, Ahmed A.M., Gumilar, Gilang, Ashok, Aditya, Rezaul Karim, Mohammad, Abdullah Alnaser, Ibrahim, Chaikittisilp, Watcharop, Ray, Nirat, Yamauchi, Yusuke, Valentino Kaneti, Yusuf
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-01-2024
• Subjects: Ammonia sensing; Gas sensors; Hierarchical three-dimensional; Metal-organic frameworks; Quartz crystal microbalance; Hierarchical three-dimensional; Quartz crystal microbalance; Ammonia sensing; Metal-organic frameworks; Gas sensors
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2023.147990

This work reports the fabrication of hierarchical Mn-Co BTC MOFs with tunable assembling sub-units and interiors for NH3 sensing by the QCM technique. The hierarchical hollow Mn-Co BTC spheres exhibit high sensitivity (ΔF = 384 Hz for 69.5 ppm of NH3), good limit of detection (1.12 ppm), high selectivity (41%), and excellent stability even after 5 months of testing.
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•Hierarchical 3D Mn-Co BTC particles with tuneable sub-units are synthesized.•Higher Mn proportion promotes 2D sub-units and hollow architecture.•The hierarchical hollow Mn-Co BTC shows high sensitivity and selectivity for NH3.•The hierarchical hollow Mn-Co BTC shows good long-term stability after 5 months.•The hollow cavities and rich carboxyl and hydroxyl sites promote NH3 adsorption.
A series of hierarchical three-dimensional (3D) manganese-cobalt BTC (Mn-Co BTC; BTC = benzene-1,3,5-tricarboxylate ) metal–organic frameworks (MOFs) with controllable sub-units and interior architectures have been synthesized at room temperature without templates, etchants, or high-pressure conditions. The assembling sub-units of the hierarchical 3D Mn-Co BTC MOFs can be controlled by tuning the Mn/Co ratio, with higher Mn content favoring one-dimensional (1D) sub-units, while higher Co content favors two-dimensional (2D) sub-units. The hierarchical hollow Mn-Co BTC spheres (M2C-BTC) exhibit a frequency change (ΔF) of 383.7 Hz to 69.5 ppm of NH3 which is ∼1.7-, 2.1-, 4.2-, and 8.3-times higher than the ΔFs of hierarchical Mn-Co BTC nanorods (M1C-BTC), hierarchical flower-like Mn-Co BTC (M0.5C-BTC), Mn-BTC nanospheres, and Co-BTC nanoplates, respectively. In addition, they exhibit low limit of detection (1.12 ppm), high selectivity (41 %) and excellent stability for NH3 sensing with a minor change of 3.1 % in the ΔF value after 5 months of testing. The superior NH3 sensing performance of the hierarchical hollow Mn-Co BTC spheres may be attributed to the hollow cavities which can enhance the adsorption rate of NH3 molecules (based on the adsorption kinetics analysis) and enable them to interact with the less accessible metallic active sites on the inner cores of this MOF. The possible sensing mechanisms include the chemisorption of NH3 molecules on unsaturated metal (Mn and Co) centers as well as the hydrogen bonding between the hydroxyl and carboxyl groups with NH3.