Summary

For the first time, the manuscript highlights the role of metal-oxide nanoparticles (MP) impregnated Metal-organic framework (MOF) as an efficient sensing material to detect the toxic Hydrogen sulphide (H2S) gas. Over the past decade, many material scientists and chemists have shown great interest in MOF because of its structural diversity, excellent inability, high surface area, high thermal, and chemical stability. However, this class of materials possesses some intrinsic limitations such as poor catalytic activity and the absence of gas-specific binding groups to selectively adsorb specific gas molecules; hence these issues impede the wide acceptance of MOF particles for building gas sensors. Owing to solve these drawbacks, authors have proposed an innovative material system that strategically impregnated the MPs into the porous MOF particles. Followed by, series of such MP-MOF particles were synthesized and successfully tested toward target H2S gas. However, the manuscript failed to address some of the crucial studies including repeatability, electrical, and ambient stability of the sensor. In addition to this, the data corresponding to the selectivity study which is crucial to understand the cross-sensitivity issues of the proposed sensor is lacking in the manuscript. Even though the manuscript has certain limitations, it has the immense potential to attract more readers of MOF nanoparticles based gas sensors. I would like to recommend the article for publication after addressing the following comments.

Merits

1. The manuscript not only handpicked one type of novel MP-MOF particle but also synthesized series of those materials having different functional groups, metal nanoparticles, and pore sizes.
2. For the first time, the manuscript presents an impactful case-study, supported by valid characterization results, highlighting the effect of functional groups and type of metal nanoparticles on the H2S sensing performance of MP-MOF.

Comments

1. Page -2 / Introduction section: Owing to support the readers with a good literature background, I would like to recommend authors to kindly add more discussions on both merits and drawbacks in using zirconium-based MOFs for room temperature gas sensing application.
2. Page -3 / Experimental section: Among the many options available in the literature, the manuscript outlines the use of NO2 and N3 as potential functional groups to modify MOF particles. It would be highly beneficial if authors can provide a detailed literature survey to justify their idea for choosing those specific functional groups.
3. Page -4 / Figures 3 and 4: In Figure 3, the authors argued that the presence of low intense Ag2O peak, in XRD plot, from MP-MOF particles is mainly due to the poor distribution of nanoparticles. In contrast to this, using Field emission scanning electron microscopy (FESEM), the authors proved that the Ag2O particles are uniformly distributed on the surface of MOF. I would like to recommend the authors to resolve the observed contradiction from the proposed results.
4. Page-8 / Figures 5 and 7: The results obtained from figure 7 is not consistent with the conclusions made from the outcomes of figure 5. The authors need to clarify this inconsistency. (Hint: Figure 5 shows that MP-MOF particles have less gas volume uptake but, using Figure 7, manuscript highlights that it has superior sensing performance)
5. Page-8 / Figure 8: Please furnish the error bar data for understanding the reliability of the provided reproducibility and sensitivity data of the sensor.
6. Page-8 / Figure 7: Besides using the target H2S, I recommend authors to test their sensors toward other gas such as Nitrogen dioxide (NO2), Ammonia (NH3), Sulphur dioxide (SO2), and Humidity (H2O) to observe the adverse effect of them on the H2S sensing performance of the proposed sensor.