An Ultramicroporous Fe(II)-Anilato MOF for CO₂ Capture and Environmental Applications

The development of sustainable porous materials for gas capture and environmental remediation is a central challenge in materials chemistry. Herein, we report the green, scalable synthesis and multifunctional integration of a novel Fe(II)-based metal–organic framework, Fe(trz₂An)·3H₂O (trz₂An = 3,6-N-ditriazolyl-2,5-dihydroxy-1,4-benzoquinone), designed for CO₂ capture and pollutant removal. The material is obtained via an optimized aqueous synthetic route under mild conditions achieving high crystallinity and yields up to 85%. The use of NH₃ as a weak base significantly enhances sustainability metrics, leading to a space–time yield of ~10,000 kg m^-3 day^-1, among the highest reported for green MOF syntheses.

Single-crystal X-ray diffraction reveals a 3D neutral framework with ultramicroporous channels (~3.8 Å), closely matching the kinetic diameter of CO₂. The structure exhibits high porosity (28.8% void volume), excellent thermal stability up to 300 °C, and remarkable stability in aqueous environments across a pH range of 3-8.

CO₂ adsorption studies show an uptake of ~2500 μmol g^-1 at 30 °C, with low differential heats of adsorption indicative of physisorption and facile regeneration. Beyond gas capture, the material demonstrates promising ion-exchange capabilities toward toxic heavy metals, such as Cd²⁺ and Pb²⁺, with uptake capacities up to 300-500 mg g^-1, highlighting its potential for water remediation.

Furthermore, the MOF has been successfully incorporated into biopolymer-based matrices, specifically carboxymethylcellulose (CMC), to form composite membranes. Ongoing studies indicate good reproducibility and promising separation performance, supporting the development of hybrid materials for practical applications.

These results establish Fe(trz₂An)·3H₂O as a versatile and scalable platform for integrated gas capture and environmental remediation technologies.