Fabrication of Pd/In₂O₃ Nanocatalysts Derived from MIL-68(In) Loaded with Molecular Metalloporphyrin (TCPP(Pd)) Toward CO₂ Hydrogenation to Methanol

Abstract

Methanol synthesis from CO2 hydrogenation with H2 produced from renewable energy has emerged as a promising method for carbon neutrality. The supported Pd/In2O3 catalyst has attracted great attention due to its superior activity and methanol selectivity, but the formation of the In–Pd bimetallic phase upon over-reduction would lead to quick catalyst deactivation. In this work, we elucidate the reduction behavior of Pd/In2O3 catalysts by using TCPP­(Pd)@MIL-68­(In) as precursors. During catalyst fabrication, metalloporphyrins (viz., TCPP­(Pd)) served as both a capping agent for the growth of MIL-68­(In) and a shuttle for transporting the Pd2+, which enhanced the dispersion of Pd0 species on In2O3–x during the calcination and reduction treatments and prevented the formation of In–Pd bimetallic phase by over-reduction. With a low Pd loading of 0.53 wt %, the resultant Pd/In2O3 catalyst exhibited a maximum methanol space–time yield of 81.1 gMeOH h–1 gPd –1 with a CO2 conversion of 8.0% and a methanol selectivity of 81% over 50 h on stream (295 °C, 3.0 MPa, 19,200 mL gcat –1 h–1). In contrast, the comparative Pd/In2O3 catalyst prepared by the impregnation of PdCl2 in MIL-68­(In) showed poor activity and stability due to the formation of InPd/In2O3–x surface structures. In addition, we found a strong connection between the reduced degree of In2O3 and the catalytic performance of the supported Pd/In2O3 catalysts by integrating catalyst characterization results with density functional theory (DFT) calculations. Interestingly, the surface In/O ratio detected by XPS can reflect information about both metal–support interaction and the amount of oxygen vacancy, which is highly related to the catalytic activity. The DFT calculation also shows that the Pd/In2O3 catalyst has excellent thermodynamic selectivity for the CH3OH product. This work provides an alternative synthetic strategy for Pd/In2O3 nanocatalysts and sheds light on the deactivation mechanism of the supported catalysts.

Hybrid MOF Template‐Directed Construction of Hollow‐Structured In2O3@ZrO2 Heterostructure for Enhancing Hydrogenation of CO2 to Methanol

“…[69] The peak observed above 200 °C can be attributed to the CO 2 chemisorption adsorbed on the oxygen vacancies, which are critical for the CO 2 adsorption and activation. [53,70] As shown in Figure 5C 2− , at 1616 and 1530 cm −1 ) were also observed due to CO 2 adsorbed on the surface hydroxyl group. [71,72] It can be seen that In 2 O 3 @ ZrO 2 showed much stronger band intensities of formates and bicarbonate species than that of other samples, suggesting the promotion of the CO 2 dissociation on ZrO 2 /In 2 O 3 heterointerfaces, as already proven by the corresponding catalytic performance data.…”

“…[ 69 ] The peak observed above 200 °C can be attributed to the CO 2 chemisorption adsorbed on the oxygen vacancies, which are critical for the CO 2 adsorption and activation. [ 53,70 ] As shown in Figure 5C, compared with bare In 2 O 3 , the ZrO 2 exhibited a higher temperature CO 2 desorption peak around 550 °C, indicating the stronger interaction of CO 2 on the ZrO 2 surface. Due to the separated In 2 O 3 and ZrO 2 phase, In 2 O 3 ||ZrO 2 showed a combination of these of bare In 2 O 3 and ZrO 2 .…”

In situfabrication of MIL-68(In)@ZnIn2S4heterojunction for enhanced photocatalytic hydrogen production

“…19 Compared with traditional semiconductors, MOFs possess high porosity, large specific surface area, adjustable pore size and structural diversity required for photocatalytic reactions, as well as simple synthesis, making MOFs an ideal candidate for photocatalytic materials. [20][21][22] Therefore, MOFs are expected to become a popular material in the field of environment and energy in the future. However, the photocatalytic activity of MOFs is largely limited by poor charge separation and transfer efficiency, inferior photochemical stability and weak photoresponse capacity.…”

Optimizing the Interfacial Environment of Triphasic ZnO-Cu-ZrO2 Confined inside Mesoporous Silica Spheres for Enhancing CO2 Hydrogenation to Methanol

“…It is well-known that the multicomponent catalysts based on metallic copper nanoparticles (Cu NPs) in combination with reducible metal oxides tend to selectively produce MeOH from CO 2 /H 2 feed gas. − In this regard, the selection of suitable oxides or other metal dopants as Cu-promoter is critical to the selectivity of a desired CO 2 hydrogenation product . Nevertheless, Cu-based catalysts themselves also confront some exclusive hurdles.…”