A simplistic approach for the synthesis of Covalent Organic Frameworks(COFs) comprising of tetrafunctionalized porphyrin and polyoxometalates to uncover catalytic applications

Abstract

Tetrafunctionalized porphyrins are energetic synthons to prepare MOFs(Metal organic framework) and COFs(Covalent organic framework). Herein, a new tetrafucntionalized metallo porphyrin was used and connected via amide functionality with anderson polyoxometalates(POMs) and assembled two COFs(P@Ni-AndCOF & P@Cu-AndCOF). Structures, properties and their relationships have been unlocked thoroughly by means of FT-IR, UV–visible, 1HNMR, PXRD, SEM and cyclic voltammetric(CV) spectral analysis. The catalysts were tested to uncover the photocatalytic properties such as photocurrent and photodegradation properties. P@Cu-AndCOF and P@Ni-AndCOF were used to fabricate the ITO TiO2 coated electrodes to study optical activity, adsorption study and photocurrent generation. The adsorption study of P@Cu-AndCOF and P@Ni-AndCOF has been studied by using Langmuir and Freundlich model with calculated Langmuir constants qm, KL and RL values of about [7.44(mg/g), 8.02(mg/g)], [0.79(L/mg), 0.69(L/mg)] and (0.22 & 0.23) respectively. The correlation coefficient for adsorption obtained through Langmuir analysis were 0.92, and 0.95 for P@Ni-AndCOF and P@Cu-AndCOF respectively. The 1/n, Kf and R2 values obtained from Freundlich adsorption isotherm for P@Ni-AndCOF and P@Cu-AndCOF were (0.50 & 0.52), (3.325676 mg/g &3.328971 mg/g) and (0.94 & 0.93) respectively. The bandgap values evaluated via absorption edge of UV–visible spectra for P@Ni-AndCOF and P@Cu-AndCOF in DMSO solution were 2.82eV, and 2.83eV respectively while the bandgap values calculated for ultra-thin films were 1.78eV, and 1.85eV for P@Ni-AndCOF and P@Cu-AndCOF correspondingly. The calculated real, imaginary dielectric constants, Urbach edge, refractive index values and the electrical conductivity for ultra-thin film of P@Ni-AndCOF and P@Cu-AndCOF were (1.4x104-1.41x104& 2.19x10−9-2.45x10−9), (6.6x104-7.4x104&1.7x10−10-2.47x10−10), (0.323eV & 0.362eV), (32.9–32.4 & 33–30.4) and (5.8 × 104-2.9 × 104 &6.1 × 104-4.7 × 103 S/m) respectively. Furthermore, photodegradation activity of both catalysts was checked in Methylene-Blue(MB) and Rhodamine B(Rh-B) dyes under 3 W light. They showed higher photocatalytic efficiency for MB than that for Rh-B caused degradation efficiency of 89% and 79.3% for MB and 83% and 71.3% for Rh-B respectively after 660min. The photodegradation activity was also observed in dyes solutions along with some scavenger's ammonium oxalate (AO, h+-scavenger) and isopropanol (ISOP, •OH-scavenger) and it was observed that by the addition of these scavengers photodegradation rate was reduced.