Photocatalytic Reduction of CO2 to Methanol Using a Copper-Zirconia Imidazolate Framework

Abstract

A set of novel photocatalysts, i.e., copper-zirconia imidazolate (CuZrIm) frameworks, were synthesized using different zirconia molar ratios (i.e., 0.5, 1, and 1.5 mmol). The photoreduction process of CO2 to methanol in a continuous-flow stirred photoreactor at pressure and temperature of 1 atm and 25 °C, respectively, was studied. The physicochemical properties of the synthesized catalysts were studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The highest methanol activity of 818.59 µmol/L.g was recorded when the CuZrIm1 catalyst with Cu/Zr/Im/NH4OH molar ratio of 2:1:4:2 (mmol/mmol/mmol/M) was employed. The enhanced yield is attributed to the presence of Cu2+ oxidation state and the uniformly dispersed active metals. The response surface methodology (RSM) was used to optimize the reaction parameters. The predicted results agreed well with the experimental ones with the correlation coefficient (R2) of 0.99. The optimization results showed that the highest methanol activity of 1054 µmol/L.g was recorded when the optimum parameters were employed, i.e., stirring rate (540 rpm), intensity of light (275 W/m2) and photocatalyst loading (1.3 g/L). The redox potential value for the CuZrIm1 shows that the reduction potential is −1.70 V and the oxidation potential is +1.28 V for the photoreduction of CO2 to methanol. The current work has established the potential utilization of the imidazolate framework as catalyst support for the photoreduction of CO2 to methanol.

Recent progress of theoretical studies on electro- and photo-chemical conversion of CO2with single-atom catalysts

“…CO 2 RR with SACs is a promising strategy for the conversion of CO 2 to hydrocarbon fuels such as CO, CH 4 , and CH 3 OH. 13,168,170…”

“…CO 2 RR with SACs is a promising strategy for the conversion of CO 2 to hydrocarbon fuels such as CO, CH 4 , and CH 3 OH. 13,168,170 The pCO 2 RR requires the following steps (Fig. 6): (1) the photocatalyst is irradiated by light.…”

“…8,9 Nowadays, due to the requirement of energy regeneration and environment protection, photocatalysts have been paid more and more attentions because of the significance in the future applications of CO 2 RR. 10–15…”

“…8,9 Nowadays, due to the requirement of energy regeneration and environment protection, photocatalysts have been paid more and more attentions because of the signicance in the future applications of CO 2 RR. [10][11][12][13][14][15] The concept of single-atom catalysis (SACs), rstly proposed by Zhang, Li, Liu et al, 16 has been widely used in heterogeneous catalysis, [17][18][19][20] which have shown the rosy prospects to achieve high activity, selectivity and ∼100% atom utilization. From then on, it had developed preternaturally fast on enabling heterogeneous reduction products.…”

Recent Advances of Photocatalytic Hydrogenation of CO2 to Methanol

“…For an effective photocatalyst, the bandgap energy must be less than 3 eV to expand the light absorption in the visible area and use solar power efficiently. To date, a variety of photocatalysts including P-and F-co-doped carbon nitride (PFCN) [15], RuSA-mC 3 N 4 [16], Cu-ZIF [17,18], single Cu 2 O particle [19,20], g-C 3 N 4 -TiO 2 [21], (Pd/Pt)SA/g-C 3 N 4 [22], O-doped g-C 3 N 4 (OCN-Tube) [23], Cu-TiO 2 [24], Ni-nanocluster loaded on TiO 2 (Ni/TiO 2 [Vo] ) [25], aerogel flow-reactor [26], porous-g-C 3 N 4 /TiO 2 -nanotube [27][28][29], carbon-doped TiO 2 [30][31][32], RGO-NH 2 -MIL-125(Ti) [33], Cu porphyrin-based MOF [34], Zn 2 GeO 4 /ZIF-8 nanocomposite [35,36], TZTZ-TA-CMP [37], graphene quantum dots [38] and In 2 O 3 -CuO [39] have been reported for photocatalytic CO 2 reduction to valuable chemicals. Figure 1 indicates that the interest of researchers is continuously growing in the field of "Photocatalytic reduction of CO 2 to methanol".…”