Engineering resilient MOFs: Balancing stability, sustainability, and toxicity in doped HKUST-1

Metal-organic frameworks (MOFs) have emerged as a versatile class of porous materials owing to their exceptionally high surface area, tunable pore architecture, and diverse applications in adsorption, catalysis, sensing, and biomedicine. Among them, the archetypal copper-based HKUST-1, exhibit exceptional textural properties that make them highly attractive for sustainable applications, including environmental remediation, heavy metal capture, and gas adsorption. However, the translation of pristine HKUST-1 into practical, real-world systems is frequently bottlenecked by two critical limitations: inherent instability and potential cytotoxicity arising from active metal leaching. This study presents a systematic approach to overcoming these barriers through the strategic doping of the HKUST-1 framework with distinct transition and rare-earth metals.

To address these limitations, this work employs metal-ion doping as a rational strategy to tailor the structural integrity and functional performance of HKUST-1. A series of Fe3+-, Zn2+-, Ni2+-, and Yb3+-doped HKUST-1 frameworks were synthesized using a one-pot hydrothermal approach. By independently incorporating these transition and rare-earth metal ions into the binuclear copper paddlewheel secondary building units, the physicochemical properties of the framework were systematically engineered while preserving its intrinsic porosity. The influence of dopant chemistry on framework crystallinity, morphology, porosity, hydrolytic stability, thermal stability, and metal-ion release was comprehensively investigated using complementary structural and physicochemical characterization techniques.

The results demonstrate that metal doping significantly enhances the structural robustness of HKUST-1 against hydrolytic and thermal degradation while maintaining its crystalline architecture. The improved framework stability reduces copper-ion leaching under aqueous conditions, thereby enhancing the long-term durability and sustainability of the material for environmental applications.
Recognizing that sustainable materials must also exhibit acceptable biological safety, the cytocompatibility of the pristine and doped HKUST-1 frameworks was systematically evaluated through in vitro studies. Cytotoxicity was assessed using MTT assays, while intracellular reactive oxygen species (ROS) generation was investigated by flow cytometry. The findings reveal that selected dopant configurations effectively mitigate the cellular toxicity commonly associated with rapid copper dissolution, resulting in more favorable biological interactions without compromising the desirable physicochemical properties of HKUST-1.

The structural stabilization achieved through this doping methodology translates directly to improved, sustainable performance, allowing the framework to maintain functional integrity during continuous environmental exposure. These independently doped HKUST-1 variants not only demonstrate superior structural retention but also exhibit modulated, favorable biochemical interactions, advancing the paradigm of safe-by-design porous materials. Ultimately, this work elucidates how tailored chemical modifications can simultaneously resolve the stability and toxicity trade-offs in HKUST-1, offering a robust foundation for developing the next generation of resilient and biocompatible MOFs for sustainable technologies.

Priya is a fourth-year Ph.D. candidate in Materials Engineering at the Indian Institute of Technology Gandhinagar (IITGN), India. Her research focuses on the design and engineering of metal–organic frameworks (MOFs), particularly metal-ion-doped HKUST-1, with emphasis on improving hydrolytic and thermal stability, understanding structure–property relationships, and evaluating cytocompatibility for sustainable environmental and biomedical applications. Her work integrates materials synthesis, advanced characterization, and biological evaluation to develop safe-by-design porous materials. Her research interests include MOFs, functional porous materials, adsorption, biomaterials, and sustainable materials engineering.