Cr-N bridged MIL-101@tubular calcined N-doped polymer enhanced adsorption of vaporous toluene under high humidity

High capacity adsorption of volatile organic compounds (VOCs) in high humidity environment is a crux but challenge for atmospheric VOCs governance. In this work, tubular carbonized N-doped polymers (TCNP) were implanted into MIL-101 via N-Cr-O interface self-assembly, enabling high adsorption for vapor toluene in high humidity. Through mechanical ball milling and carbonization, Cr ions were preloaded on TCNP to form highly dispersed 3-5 nm Cr-N crystallite as anchors for growing MIL-101(Cr/Cu). Newly constructed smaller micropores of 6.8 angstrom with aromatic rings/N sites at the interface and doped Cu ions in MOF framework synergistically enhanced pi-pi conjugation and electrostatic interaction for C7H8 molecules. This endowed [TCNP5/MIL(Cr/Cu)](N-Cr) 2.9 times higher toluene uptake (6.34 mmol/g) at low vapor pressure (P/P-0 = 0.02) and 1.9 times diffusivity under high humidity (60% RH) than that of MIL-101(Cr) at 298 K. The adsorption breakthrough curves for vaporous toluene showed that TCNP@MIL-101(Cr/Cu) exhibited outstandingly higher adsorption equilibrium capacity (2.7 mmol/g) under 80% RH, corresponding to approximately 2-10 times than those of reported state-of-the-art adsorbents under similar conditions. This study provided a novel interface construction strategy for hydrophobic MOF composites, which supplied deeper understanding for VOCs adsorption and promoted MOFs practical application in VOCs capture under humid environment.

Automated summary

In this study, tubular carbonized N-doped polymers (TCNP) were implanted into MIL-101 via N-Cr-O interface self-assembly, allowing for high adsorption of vapor toluene in high humidity conditions. The preloading of Cr ions on TCNP and the construction of smaller micropores at the interface synergistically enhanced the adsorption capacity and diffusivity of the materials. The newly developed TCNP@MIL-101(Cr/Cu) composite exhibited significantly higher adsorption equilibrium capacity compared to state-of-the-art adsorbents under similar conditions.