Ferrocene-Based Porous Organic Polymer (FPOP): Synthesis, Characterization and an Electrochemical Study

Round 1

Reviewer 1 Report

The manuscript has been updated.

Author Response

Reviewer 1

Authors: Thank you for your comments and to accept the manuscript for publication in Electrochem.

Reviewer 2 Report

In this work, a new porous ferrocene based organic polymer (FPOP) was designed and prepared via two different strategies: bottom-up and post-synthetic modification approaches. The materials were well characterized and analyzed by XRD, Porosimetry, FTIR. NMR, and thermal analysis. The mechanism of FPOP formation was thoroughly analyzed. The electrochemical studies were performed via 3-electrode and 2-electrode configurations. The FPOP, prepared by post-synthetic modification method, shows a great electrochromic property.

Overall, the manuscript was well written. Therefore, I would suggest a minor revision before acceptance.

1. For FTIR analysis, the author did not show any spectra of two FPOP polymers.
2. The author should state whether the adsorption or desorption branch of the isotherm was used for the NLFDT calculation.
3. As the main difference of two synthesized FPOP polymers was its porosity, the N₂ adsorption-desorption isotherm and pore size distribution should be shown for FPOP (Strategy A), rather than only one curve for FPOP (Strategy B)
4. Including testing of commercial ferrocene, the electrochemical performance of FPOP (Strategy B) should also be compared with FPOP (Strategy A).

Author Response

Reviewer 2 (R2) considered that “In this work, a new porous ferrocene based organic polymer (FPOP) was designed and prepared via two different strategies: bottom-up and post-synthetic modification approaches. The materials were well characterized and analyzed by XRD, Porosimetry, FTIR. NMR, and thermal analysis. The mechanism of FPOP formation was thoroughly analyzed. The electrochemical studies were performed via 3-electrode and 2-electrode configurations. The FPOP, prepared by post-synthetic modification method, shows a great electrochromic property.

Overall, the manuscript was well written. Therefore, I would suggest a minor revision before acceptance.”

Authors: Thank you for your comments. The authors following the comments/questions of reviewer 2 tried to improve the parts of the manuscript in accordance to it and we hope that the manuscript could be accepted for publication in Electrochem.

R2: For FTIR analysis, the author did not show any spectra of two FPOP polymers.

Authors: The authors thank you for your comments and the spectra and the description of the NMR and FTIR were added to the ESIand figure S6 and S7.

R2: The author should state whether the adsorption or desorption branch of the isotherm was used for the NLFDT calculation.

Authors: The following changes were made in the paper according to reviewer comments: “The Brunauer-Emmet-Teller (BET) specific surface area obtained by nitrogen adsorption isotherm at 77 K of the ferrocene modified Bakelite indicated a type IV isotherm (mesoporous material) and a BET area of 52 m² g^-1 (Figure 4b). The pore size distribution (see the inset of Figure 4b), calculated by NLDFT model from desorption branch N₂ at 77 K on carbon cylindrical/slit pores, showed two pore sizes: 12 Å and 53 Å, matching with the isotherm type. The hysteresis at the desorption branch could also indicates that there is some degree of pore flexibility, which might be due to the low-barrier rotation of the ferrocene moiety. This possible structural flexibility might be one the reasons for the low crystallinity, as noted above. This same behavior is observed in materials that form nanosheets, whose stacking can generate a structural disorder [46]. The product prepared by Strategy A exhibited a much lower BET specific surface area (5 m² g^-1), suggesting that there was no formation of a porous material (see Figure S1). “

Between lines 202 and 210 from page 5 and 6.

Also changed figure S1 to figure S2 in line 248 from page 7 and figure S2 to figure S3 in line 314 from page 9

R2: As the main difference of two synthesized FPOP polymers was its porosity, the N₂ adsorption-desorption isotherm and pore size distribution should be shown for FPOP (Strategy A), rather than only one curve for FPOP (Strategy B)

Authors: The authors thank you for your comments and the changes were made in the ESI as follow:

Analysis

The surface areas and pore size distribution were found by N₂ adsorption/desorption, in the Quantachrome Nova 2200e. The isotherms were measured using a liquid nitrogen bath (77 K). The P/P₀ relative pressure values for the BET area were chosen from 5x10^-3 to 0.3 (Multi-BET). The pore size was determined using the NLFDT (Non-local Density Functional Theory) method, slit/cylindrical pore, whose calculation model was based on carbon adsorbate. The total pore volume V_pwas calculated from the nitrogen adsorption data at relative pressure P/P₀ ≈ 0.98 – 0.99 and the pore size distribution was calculated from the desorption curve.

N₂ adsorption and desorption curves for FPOP (Strategy A)

The product prepared by Strategy A showed a much lower BET specific surface area (5 m² g^-1), indicating that there was no formation of a porous material (Figure S1).

Figure S1. N₂ adsorption/desorption isotherm for FPOP (Strategy A), typical of non-porous materials.

R2: Including testing of commercial ferrocene, the electrochemical performance of FPOP (Strategy B) should also be compared with FPOP (Strategy A).

Authors: The authors thank you very much for your pertinent question, but the authors just used the better FPOP for the electrochemical studies. The one synthesised by strategy A presented the best results in porous size and for some electrochemical and energy applications is a fundamental aspect.