The effect of different reaction media on photocatalytic activity of Au- and Cu-decorated zeolitic imidazolate Framework-8 toward CO2 photoreduction to methanol

In carbon capturing processes, developing efficient technologies to convert CO2 into added-value chemicals is of enormous interest. Here, in continuation of our earlier works, the influence of various reaction media in the conversion of CO2 to methanol through a photocatalytic system using Cu- and Au-decorated zeolitic imidazolate framework-8 (ZIF-8) nanocomposites (Au/ZIF-8, and Cu/ZIF-8) has been explored. To this purpose, different analytical techniques like XRD, FT-IR, EDS, FESEM, TEM, BET, PL spectroscopy, and DRS have been employed to confirm the textural properties as well as band gap estimation of the photocatalysts. Then, the activity of the as-made nanocomposites towards CO2 reduction to methanol in the presence of UV/Vis irradations at different reaction media is assessed by a batch reactor system. The obtained results indicated that when 0.1 M Na2SO3 and 0.2 M NaOH solutions are utilized instead of pure water, the yield of methanol produced in the presence of pristine ZIF-8 increases by roughly 5 and 3 times, respectively. Furthermore, it was observed although Au/ZIF-8, and Cu/ZIF-8 nanocomposites exhibited narrow band gap energy compared to pristine ZIF-8, they didn't reveal noticeable activity when they were employed in a pure water as reaction media. Both Au/ZIF-8 and Cu/ZIF-8 photocatalysts show exceptional yields of 2650 mu mol.g(cat)(-1) and 2240 mu mol.g(cat)(-1) when 0.1 M Na2SO3 solution is used, compared to 1300 mu mol.g(cat)(-1) for pristine ZIF-8 at the same medium. We believe that the decoration of MOF materials with Au and Cu nanoparticles (NPs) can benefit because of the high surface area of MOF structures and the good photocatalytic activity of Cu and Au NPs for photoreduction of CO2, if an appropriate medium is chosen for the reaction.

Automated summary

This study explores the photocatalytic performance of Cu- and Au-decorated nanocomposites in converting CO2 into methanol in different reaction media. The results indicate that the yield of methanol is significantly increased when using 0.1M Na2SO3 and 0.2M NaOH solutions.