Seed-mediated synthesis of a modified micro-mesoporous MIL-101(Cr) for improved benzene and toluene adsorption at room conditions

Abstract

The modification of metal-organic frameworks (MOFs) for enhanced volatile organic compounds (VOCs) removal is a huge challenge. Therefore, it is of great importance to find a proper strategy to tune the porosity of MOFs and their VOCs removal performance. In this study, we report a novel seed-mediated synthesis strategy using a low-cost and heteroatom-rich carbon structure (MIC-COOH) to prepare hierarchical micro-mesoporous MIL-101(Cr). Different amounts of MIC-COOH were applied to investigate the efficiency of seed concentration on the fundamental specification of the created hierarchical MIL-101(Cr) and its benzene and toluene uptake. The results showed that the increase of MIC-COOH significantly enhanced the mesoporous volume in the MOF structure, resulting in the creation of large surface area (up to 2971.5 m2/g) and high pore volume (up to 2.21 cm3/g). MIL@MIC-4% nanostructure exhibited 235.3 ± 0.05 and 291.6 ± 0.04 wt% adsorption efficiency for benzene and toluene, respectively, which are ⁓3.0 and 4.1 times greater than those of pristine MIL-101(Cr). It also exhibited higher cyclic adsorption efficiency than that of the pristine MIL-101(Cr) after five consecutive adsorption-desorption cycles. The uptake behavior of benzene and toluene on the modified MIL@MIC structure was also perused by applying density functional theory (DFT) calculations. According to the findings, it was revealed that the cooperative charge transfers between MIL-101(Cr) and MIC-COOH through the structure can play an efficient role in the enhanced uptake of benzene and toluene molecules.