Functionalizing the recently developed porous materials such as porous organic frameworks and coordination polymer networks with active homogeneous catalytic sites would offer new opportunities in the field of heterogeneous catalysis. In this regard, a novel covalent triazine framework functionalized with an Ir(III)-N-heterocyclic carbene complex was synthesized and characterized to have a coordination environment similar to that of its structurally related molecular Ir complex. Because of the strong σ-donating and poor π-accepting characters of the Nheterocyclic carbene (NHC) ligand, the heterogenized Ir-NHC complex efficiently catalyzes the hydrogenation of CO 2 to formate with a turnover frequency of up to 16 000 h −1 and a turnover number of up to 24 300; these are the highest values reported to date in heterogeneous catalysis for the hydrogenation of CO 2 to formate.
A heterogenized catalyst on a highly porous covalent triazine framework was synthesized and characterized to have a coordination environment similar to that of its homogeneous counterpart. The catalyst efficiently converted CO2 into formate through hydrogenation with a turnover number of 5000 after 2 h and an initial turnover frequency of up to 5300 h(-1) ; both of these values are the highest reported to date for a heterogeneous catalyst, which makes it attractive toward industrial application. Furthermore, the synthesized catalyst was found to be stable in air and was recycled by simple filtration without significant loss of catalytic activity.
One bottleneck in
the realization of CO2 conversion
into value-added compounds is the lack of catalysts with both excellent
activity and recyclability. Herein, a catalyst is designed for the
hydrogenation of CO2 to formate to boost up these features
by considering the leaching pathway of previously reported heterogenized
catalyst; the design strategy incorporates oxyanionic ligand(s) in
the coordination sphere to provide a pathway for both preventing the
deleterious interactions and assisting the heterolysis of H2. The tailored heterogenized catalyst, [bpy-CTF-Ru(acac)2]Cl, demonstrated excellent recyclability over consecutive runs with
a highest turnover frequency of 22 700 h–1, and produced a highest formate concentration of 1.8 M in 3 h. This
work is significant in elucidating new principles for the development
of industrially viable hydrogenation catalysts.
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