Configuration of hetero-framework via integrating MOF and triazine-containing COF for charge-transfer promotion in photocatalytic CO2 reduction

Abstract

Photocatalytic CO2 reduction into high value-added chemicals is of considerable prospect for tackling quandaries in energy scarcity. One potent strategy to raise up its conversion efficacy is engineering heterostructure by virtue of tunable substituent in organic structure to facilitate the charge delivery within the photocatalyst. Herein, three metal organic frameworks (MOFs) built by the same ligand but different metal ions, are in-situ grown onto a triazine-containing covalent framework (COF), TP-TA, resulting in three hetero-frameworks, namely, In-MOF@TP-TA, Zr-MOF@TP-TA and Fe-MOF@TP-TA (In-MOF, Zr-MOF and Fe-MOF are abbreviations for NH2-MIL-68(In), NH2-UiO-66(Zr) and NH2-MIL-101(Fe) MOFs, respectively). Owning to the configured type-II heterojunctions that apparently suppress the charge recombination, the light-driven CO2 reduction reaction (CO2RR) manipulated by the three hybrids behave higher catalytic performance by contrast to the pristine MOFs or COF. Amid the three heterostructure, In-MOF@TP-TA provides the optimal catalytic activity, giving the CO and CH4 production rate as 25 and 11.67 μmol·g−1·h−1, respectively. In addition, their photocatalytic activities follow the order as In-MOF@TP-TA > Zr-MOF@TP-TA > Fe-MOF@TP-TA, consisting with the CB potentials of the MOF components (from negative to positive) and in turn certifying the charge flowing orientation within the type-II heterostructure. Our work broadens the rational design for the covalently integrated heterostructures as well as their melioration in photocatalytic CO2RR.