A highly efficient and reusable amorphous Pd(ii)/crystal Pd(0)-grafted porous polymer framework for catalytic CO2 cycloaddition†
c
and
Sk. Manirul
Islam
*a
Abstract
A simple porous polymer framework (PPF) as a promising heterogeneous ligand for the Pd-catalyzed CO2 fixation reaction into diverse cyclic carbonates is reported. Several terminal epoxides and more challenging disubstituted epoxides were efficiently converted into value-added cyclic carbonates with satisfactory to excellent yields (i.e., 65 to 99% yields) and excellent selectivities (>99%) using an imine-linked Pd-based PPF catalytic system (namely, Pd@3D PPF) as an efficient catalyst and tetrabutylammonium bromide (TBAB) as a co-catalyst under mild conditions (1 atm CO2 pressure and room-temperature) without employing any solvents. Notably, the Pd-loaded PPF catalyst can be separated and reused over five times without significant loss of catalytic performance and selectivity for the cycloaddition of CO2 to epoxides. This intuitively appealing methodology tolerates a wide variety of functional groups and opens an avenue for Pd-based imine-linked frameworks as a reliable platform to control regioselectivity.
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