Visible light driven CO2 reduction to methanol by Cu-porphyrin impregnated mesoporous Ti-MCM-48

Mesoporous Ti-MCM-48 photocatalyst, with Si/Ti (wt/wt) ratio of 100,50 and 25 was effectively applied for CO2 reduction into methanol under UV-visible light irradiation bearing mid gap energy states and Ti3+ sites. The bare Ti-MCM-48 with Si/Ti (wt/wt) ratio of 25 displayed highest photocatalytic methanol yield (85.88 mu mol g(-1 )L(-1))with a BET surface area of 1528 m(2) g(-1) and mid gap energy states as determined from the XPS analysis, compared to the other composite ratios. The Ti-MCM-48(25) impregnated with Cu-porphyrin (CuTPP) resulted in methanol yield of 297 mu mol.g(-1) under 33 mW.cm(-2) simulated light intensity, using 0.1 M Na2SO3 in 0.1 M NaOH as supporting electrolytes, which is 3.45 times higher than the bare Ti-MCM-48(25) due to the visible light excitation of the porphyrin macrocycle and charge transition from the lowest occupied molecular orbital (LUMO) of CuTPP to the Ti(3+ )metal centers. Also, methanol yield was studied with CO2 gas-liquid mass transfer and mass transfer limitations prevailing in the reactor. Mass transfer limitation experiments revealed that metal loading, catalyst concentration, stirring speed and light intensity influence the methanol yield. (C) 2018 Elsevier B.V. All rights reserved.