Metal Organic Framework-Enhanced 3D-Printed Monoliths for Water Filtration: Tackling Structural Integrity with Higher Adsorption

Abstract

Access to clean water remains unattainable due to water pollution caused by various sources. Conventional water purification methods fall short of eliminating micro-sized and soluble contaminants, promoting the exploration of innovative approaches utilizing nanomaterials. Thus, metal-organic frameworks (MOFs) have attained considerable attention for water filtration, exhibiting high pollutant adsorption potential due to their abundant and well-organized nanoporous structure. However, a major limitation of MOFs is secondary contamination arising from MOFs leaching and detaching from the substrate on which they are synthesized. Herein, we propose a novel design and manufacturing of MOF-laden monolith 3D structure (MLMS) to minimize such drawbacks. Using extrusion-based additive manufacturing, we constructed the MLMS with macroscale porosity, employing a Moiré pattern to enhance its mechanical strength in different dynamic fluid conditions. Copper-based MOFs (Cu-MOFs) were integrated within the MLMS with high adhesion by the introduction of heat treatment, thereby minimizing leaching and detaching while maintaining the pollutant absorption capability. Furthermore, the Cu-MOFs’ growth, distribution, and adsorption efficiencies have been studied by growing them on various commercially available 3D printing polymers [polylactic acid, polyethylene terephthalate glycol (PETG), acrylonitrile butadiene styrene, and thermoplastic polyurethane]. The results show that the surface area covered by the MOFs ranges from 12.8% to 75.8% depending on the number synthesis cycle. In addition, a reduced leaching rate of 16.1% from the MLMS was observed at a high-water flux (4.14 × 10³ L m⁻² h⁻¹), demonstrating significant adhesion between the MLMS and Cu-MOF nanoparticles. The adsorption efficiency of malachite green dye was further analyzed with Cu-MOFs@MLMS, showing removal efficiency of 94.77% and 36.42% under stagnant and dynamic flow (1.18 × 10³ L m⁻² h⁻¹) conditions, respectively, when MLMS was made of PETG. The findings reveal the MLMS’ potential in removing contaminants under both stationary and flowing systems and the broad applicability of MOFs-loaded 3D-printed monoliths for scalable and efficient water filtration systems.