A 2D layered cobalt-based metal–organic framework for photoreduction of CO2 to syngas with a controllable wide ratio range

Abstract

Photocatalytic CO₂ reduction to syngas (a mixture of CO and H₂) with adjustable composition is a prospective way to mitigate the energy shortage and the greenhouse effect. Herein, we synthesize a thermally stable two-dimensional cobalt-based metal–organic framework (denoted as “Co-TBAPy”) consisting of cobalt metal centers and H₄TBAPy (1,3,6,8-tetrakis(p-benzoic acid) pyrene) as an organic linker, which exhibits superior CO₂ adsorption capability and a considerable specific surface area. In accordance with the energy levels of [Ru(bpy)₃]Cl₂·6H₂O as a sensitizer, Co-TBAPy is active for photocatalytic reduction of CO₂ to syngas with a wide controllable ratio range between 0.14 and 1.65 under visible-light irradiation. Moreover, the proportion of CO : H₂ = 1 : 2 and 1 : 3 favorable for the synthesis of methanol and methane, respectively, can be precisely regulated, which few MOF-based photocatalysts have achieved so far. Furthermore, combined with DFT calculation, we reveal the influence of the water content of the reaction system in the process of photocatalytic CO₂ reduction to produce a controllable proportion of syngas, which is often a profound while elusive factor in photoreduction reactions. This work provides a feasible concept for the design and application of Co-MOF materials for the photoreduction of CO₂ to syngas in practical industrial fields.