UiO-67 metal-organic frameworks with dual amino/iodo functionalization, and mixed Zr/Ce clusters: Highly selective and efficient photocatalyst for CO2 transformation to methanol

Abstract

Metal-organic frameworks (MOFs) are promising tools for photocatalytic CO2 reduction (PCR) to produce valuable added-value products. However, existing MOFs demonstrate significantly weaker potential for PCR to MeOH compared to fuels like CO, CHOOH, and CH4. This study address this challenge by exploring a series of bifunctional UiO-67 MOFs containing NH2 and I groups with varying Ce to Zr metal node ratios (0, 10, 20, 29, and 40 % Ce). These MOFs, denoted as Zr/CeX%-UiO-67(NH2, I), were probed for their ability to convert CO2 to MeOH under solar irradiation without the need for a photosensitizer. The results demonstrate a remarkable increase in both selectivity and efficiency for MeOH production with increasing Ce content. Notably, Zr/Ce29%-UiO-67(NH2, I) achieves 100 % selectivity for MeOH production, along with MeOH productivity of 44.7 µmolh−1g−1, significantly surpassing previously reported UiO-based MOFs for PCR-to-MeOH conversion. Furthermore, this MOF exhibits exceptional CO2 uptake capacity compared to pristine UiO-67 and many established MOFs, further highlighting its catalytic efficacy. The outstanding photocatalytic performance of Zr/Ce40%-UiO-67(NH2, I) can be attributed to a synergistic combination factors: (i) the optimal incorporation of redox-active Ce metal sites, (ii) enhanced CO2 capture facilitated by the cooperative interaction of NH2 and I groups, and (iii) the introduction of amino functions that broaden the light absorption range of the MOF. This work demonstrates a successful strategy for incorporating various functionalities into MOFs, paving the way for the design of highly selective and efficient PCR catalysts for MeOH production.