Highly porous Zr-MCM-48 immobilized Cu-porphyrin for photocatalytic reduction of CO2 to methanol in a slurry reactor

This study involves the development of novel mesoporous Zr-MCM-48 photocatalyst impregnated with Cu-porphyrin (CuTPP) having Si/Zr ratio of 100, 50 and 25. The synthesized materials were applied as hybrid photocatalyst affording mid-gap energy states and Zi3+ sites for reduction of CO2 into methanol selectively using UV–Visible light treatment. Interestingly, Zr-MCM-48 displayed significant photocatalytic reduction ability under UV–Vis wavelength. The bare Zr-based MCM-48(25) matrix with maximum Zr content in catalyst enhanced the photocatalytic activity with 47.5 µmol methanol formation, possessing high surface area SBET of 1324 m2 g−1, under UV–Visible light irradiation. The characterization results highlighted the influence of visible light active Cu-porphyrin interaction over Zr-MCM-48 silica frameworks due to transition of electrons from the porphyrin centres to the active Zr sites as evident from DRS analysis. Moreover, the impregnation of Cu-porphyrin over Zr-MCM-48(25) displayed methanol formation about 365.11 µmol under UV–Visible light using 0.1 M NaOH and 0.1 M Na2SO3. Also, the effect of varying reaction conditions shown that catalyst concentration, metal loading, light intensity and stirring speed pronouncedly impact the formation of methanol.