(253c) Gallate-Based Metal-Organic Framework As a Heterogeneous Catalyst for the Coupling of CO2 and Epoxides

Carbon
dioxide (CO₂) is the major greenhouse gas and its increasement in
the atmosphere has evoked global environmental and societal concerns. The
chemical transformation of CO₂ into value-added chemicals has
attracted significant interest due to its great potential as a nontoxic,
ubiquitous and sustainable C₁ resource. [1] The conversion of CO₂
into cyclic carbonates, which have wide applications as pharmaceutical, fine
chemical intermediates, monomers for the production of polycarbonates, and
aprotic polar solvents, is one of the most promising strategies because of its
high atom efficiency. Although homogeneous catalysts have been industrialized
for the production of cyclic carbonates, the processes still suffer from
unviable catalyst recovery process and difficult product purification as well as
extreme pressure and temperature conditions. [2] Hence, the design and
preparation of highly efficient heterogeneous catalyst is of great significance to
boost the cyclization of CO₂ and epoxides. Metal-organic frameworks (MOFs),
which feature structural versatility, modularity, and amenability to be
designed with specific functionality, have received much attention in
catalysis, adsorption, and so on. [3-4] In
view of their ordered porous structure, hydrophobic confined environment, and
fruitful functionalizations, MOFs have been explored as one of the most
appropriate materials for heterogeneous catalysis.

In the present work, we employed gallate-based
metal-organic frameworks (M-gallate, M= Ni, Co, Mg, Mn) as a highly efficient
and recyclable heterogeneous catalyst for CO₂ cycloaddition with
epoxides in the presence of quaternary ammonium salts
under solvent-free conditions. Experimental investigations revealed that
Co-gallate shows superior catalytic activity to other M-gallate (M= Ni, Mg, Mn)
and cobalt salts. This protocol is compatible with a plethora of terminal
epoxides and consequently provides a practical alternative method for the
fixation of industrial CO₂ into value-added cyclic carbonates.

Scheme 1. M-gallate
catalyzed CO₂ cycloaddition with epoxides

Figure 1. CO₂
cycloaddition with epoxide with different catalysts

References

[1] Song QW, Zhou ZH, He LN. Efficient, Selective
and Sustainable Catalysis of Carbon Dioxide. Green Chem. 2017; 19
(16): 3707-3728.

[2] Gao CY, A J, Tian HR, et al. An ultrastable
zirconium-phosphonate framework as bifunctional catalyst for highly active CO₂
chemical transformation. Chem. Commun. 2017, 53, 1293-1296.

[3] Kurisingal JF, Babu R, Kim S-H, et al.
Microwave-induced synthesis of a bimetallic charge-transfer metal organic
framework: a promising host for the chemical fixation of CO₂. Catal.
Sci. Technol. 2018; 8, 591-600.

[4] Babu R, Roshan, R, Kathalikkattil AC, et al.
Rapid, Microwave-Assisted Synthesis of Cubic, Three-Dimensional, Highly Porous
MOF-205 for Room Temperature CO₂ Fixation via Cyclic Carbonate
Synthesis. ACS Appl. Mater. Interfaces. 2016; 8, 33723-33731.