Zn-MOF as a Single Catalyst with Dual Lewis Acidic and Basic Reaction Sites for CO₂ Fixation

Abstract

Continuous increase in carbon dioxide (CO 2 ) emissions are causing imbalances in the environment, which impact biodiversity and human health. The conversion of CO 2 to cyclic carbonates by means of metal−organic frameworks (MOFs) as a heterogeneous catalyst is a prominent strategy for rectifying this imbalance. Herein, we have developed nitrogen-rich Zn (II) based metal−organic framework, [Zn(CPMT)(bipy)] n (CPMT = 1-(4-carboxyphenyl)-5-mercapto-1Htetrazole; bipy = 4,4′-bipyridine), synthesized via a mixed ligand strategy. This Zn-MOF showed high chemical stability in both acidic and basic conditions, and in organic solvents for a long time. On account of the concurrent presence of acid− base active sites and strong chemical stability under abrasive conditions, this Zn-MOF was employed as an effective catalyst for the coupling of CO 2 and epoxides, under atmospheric pressure, mild temperature, and neat conditions. This Zn-MOF shows remarkable activity by producing high yields of epichlorohydrin carbonate (98%) and styrene carbonate (82%) at atmospheric CO 2 pressure, 70 °C temperature, and 24 h reaction time, with turnover numbers (TON) of 217 and 181, respectively. The Zn-MOF could be reused for up to seven cycles with structural and framework integrity. Overall, this work demonstrates the synthesis of a novel and highly efficient MOF for CO 2 conversion.

In Situ Pyrolysis of ZIF-67 to Construct Co2N0.67@ZIF-67 for Photocatalytic CO2 Cycloaddition Reaction

“…The relatively higher catalytic activity of 1-tert-butoxy-2,3-epoxypropane over 1-butoxy-2,3-epoxy-propan can be ascribed to the electron-donating nature of 1-tert-butoxy-2,3-epoxypropane (entries 3–4, Table ). , …”

Utility of a Copper-Embedded Porous Organic Polymer for Visible-Light-Triggered Green Hydrogen Production and CO2 Reduction

“…Several semiconductor photocatalytic systems like pure titania, titania-loaded composite catalytic systems, − metal oxide-containing WO 3 , silicon carbide, silicon-doped titanium dioxide (TiO 2 ), and NiO-based InTaO 4 systems , were constructed and have been employed as light-absorbing semiconductor catalysts for efficient catalytic reduction of CO 2 to methanol. Additionally, heterogeneous catalysis plays a crucial role in organic synthesis providing a wide spectrum of important transformations (e.g., conversion of CO 2 into valuable chemicals and fuels) over decades, − and heterogeneous Cu-based catalysts are materials used in a wide range of chemical transformations. − In recent times, numerous Cu-based photo- and photoelectrocatalysts have been employed for the reduction of CO 2 and hydrogen production. − These advantageous features for efficient chemical transformations encouraged us to develop an appropriate methodology.…”

Robust {Pb10}-Cluster-Based Metal–Organic Framework for Capturing and Converting CO2 into Cyclic Carbonates under Mild Conditions

“…Metal–organic frameworks (MOFs), as a type of highly ordered crystalline porous coordination polymers generated from the self-assembly of organic linkers and metal cations (or clusters) under suitable reticular-chemistry conditions, have sparked a strong interest of researchers because of their promising applications such as heterogeneous catalysis, energy storage, gas separations and storage, luminescence sensing, magnetism, and biomedical research. − So far, countless MOFs with unique structural properties such as high specific surface area, active metal sites, and tunable pore structures have been achieved by changing the composition of ligands or metal ions. Although the application of MOFs largely depends on their pore structure, to functionalize the inner and outer surfaces of host frameworks with some functional groups has also aroused great interest because their performance can be adjusted. − Typical methods for functionalizing MOFs include generating open metal sites (OMS), modifying with Lewis basic sites (LBS) such as pyridine, imidazole, and amide moieties, and introducing polar functional groups such as hydroxides, halides, and carboxylates. − At present, compared with commonly used metal ions, such as the first transition metal ion and rare earth ions, MOFs constructed from lead­(II) ions are relatively fewer.…”