Three-Dimensional Interlocked Crystalline Frameworks for Photocatalytic CO2 Conversion

Three-dimensional (3D) interlocking frameworks are attracting increasing research attention owing to their intriguing mechanical properties, large surface areas, and rich open sites. The study in this paper entailed the first use of tuning solvents to realize the synthesis of metal–organic frameworks (MOFs) and metallosalen-based covalent–organic frameworks (COFs) with similar 3D interlocked structures from the same precursors. These interlocking crystalline frameworks are efficient catalysts for CO₂ photoreduction. Our study is the first to investigate the impact of differences in the metal coordination environment within structurally similar COFs and MOFs in CO₂ photoreduction activity. Among the materials tested, the photocatalytic performance of the M-N₂O₄-MOFs (M = Zn, Co, and Ni) was found to be superior to that of their M-N₂O₂-COF counterparts. Notably, the Ni-N₂O₄-MOF achieved a CO production rate of 3.96 mmol g⁻¹ h⁻¹ and a CO selectivity of 93.7%. In contrast, the Ni-N₂O₂-COF exhibited a production rate of only 0.64 mmol g⁻¹ h⁻¹ with a 61.1% CO selectivity. Furthermore, a descriptor for the CO evolution rate was derived from the conduction band minimum and the reaction energy of the rate-determining step, which are two key factors influencing photocatalytic activity. This study opens up new avenues for employing interlocking crystalline frameworks in the efficient photoreduction of CO₂.