Critical Role of CUS in the Au/MOF-808(Zr) Catalyst for Reaction of CO₂ with Amine/H₂ via N-Methylation and N-Formylation

Abstract

MOF-808­(Zr) with the coordinated unsaturated (CUS) Zr4+ centers was synthesized by the thermal reflux method, and a series of Au/MOF-808­(Zr) catalysts with different Au loading percentages have been prepared by the impregnation–reduction method. The related X-ray diffraction, Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption–desorption, Inductively coupled plasma-mass spectrometry, and NH3 temperature-programmed desorption characterizations have been undertaken to understand the structure of catalysts. The catalytic activity in CO2 with aniline/H2 to N-methylation and N-formylation has been studied in a batch reactor. Results show that the MOF-808­(Zr) structures in catalysts are of high quality and damage-free. The Au nanoparticles (NPs) are highly dispersed on the surface of the MOF-808­(Zr) cage with a mean size of 2–20 nm. Also, the catalysts could catalyze the conversion of CO2 with aniline/H2 to N-methylation and N-formylation products with a high efficiency. With a 3.0 wt % Au/MOF-808­(Zr) catalyst, the conversion of aniline is 18.4%, and the selectivity of N-methylaniline is 80.9% and that of N,N-dimethylaniline is 19.1%. The preliminary reaction mechanism and the critical role of CUS were also studied. It is determined that H2 is adsorbed and activated on Au NPs. CO2 is adsorbed on the CUS Zr4+ acidic sites and O2– basic sites. The primary and secondary amines are adsorbed on the CUS Zr4+ acidic sites, where they react with CO2 and H2 to form N-formamide. Subsequently, N-formamide reacts with activated H2 to yield N-methylamine.

Fabrication of a novel heteroepitaxial structure from an MOF-on-MOF architecture as a photocatalyst for highly efficient Cr(vi) reduction

“…There were two more absorption peaks at 656 cm À1 and 457 cm À1 corresponding to the metal-O vibration, which proved the successful interaction of -COO and the metal to form the frameworks. 41 The thermal stability of the as-synthesized frameworks and their weight loss were examined by thermal gravimetric analysis (TGA) and derivative thermogravimetry (DTG), as shown in Fig. 1c.…”

Recent Trends in Upgrading of CO2 as a C1 Reactant in N‐ and C‐Methylation Reactions

“…In the same year, Ji and co‐workers examined Au/MOF‐808(Zr) catalyst for the N ‐methylation and N‐ formylation of different amines using CO 2 as a C1 reactant [24] . The authors adapted impregnation and reduction‐method techniques to prepare the Au‐based catalyst by loading different quantities of Au on the MOF‐808(Zr) molecule.…”

“…In all the steps, Au nanoparticles serve as the hydrogenation active centers for CO 2 adsorption and intermediate amides. The reaction performances at different H 2 /CO 2 pressure ratios are presented in Table 2 [24] …”

An Overview of Enabling Catalysts for Carbon Dioxide Conversion Aiming at the Two-carbon Target

“…In addition, the heterogeneous catalyst of UiO-66-Gua0.2(s) showed great versatility and better recovery in the conversion of other epoxides. Mu et al (2020) prepared MOF-808(Zr) catalysts with ligand-unsaturated Zr 4+ centers by a thermal reflux method and a series of catalysts with different Au/MOF808(Zr) catalysts with different Au/MOF808 (Zr) loading rates were prepared by impregnation reduction.…”