Petroleum-based packaging materials (“plastics”) are widely used in modern society because of their robustness, flexibility, cheapness, versatility, and low weight [1]. However, the poor sustainability and biodegradability of plastics is currently a major concern since they may negatively impact the environment. For instance, the degradation of packaging materials leads to the formation of microplastics and nanoplastics, which can damage ecosystems [2]. In response, many industries are shifting towards the utilization of biodegradable packaging materials derived from natural sources, such as biopolymers.

Indeed, there has been great interest in the development of innovative packaging materials that are more sustainable and environmentally friendly than traditional plastic-based ones [3,4]. These packaging materials often contain additives that provide novel or improved functional attributes, including mechanical, barrier, scavenging, sensing, and preservative properties [5,6]. Recently, researchers have become interested in the potential of using zeolite imidazole frameworks (ZIFs) as an additive in packaging materials because of their unique structural and physicochemical properties [7]. The term “zeolite” was first used by Axel Fredrick Cronstedt in 1756. Zeolites are porous crystalline materials, consisting of silicon, aluminum, or phosphate tetrahedra atoms linked together with oxygen atoms, which have pore sizes that range from the nanometer to micrometer ranges (4–12 A) (See Fig. 1). Zeolites can be categorized into two groups: natural and synthetic. Natural zeolites are mostly produced from sedimentary and volcanic rocks under different environmental conditions while, synthetic zeolites are made by heating of clay, soda ash, feldspar, and other mineral-rich resources [[8], [9], [10]].

ZIFs are a subset of metal-organic frameworks (MOFs), which are comprised of divalent metal ions or clusters (e.g., Zn2+ or Co2+) coordinated with nitrogen atoms in imidazole organic linkers (e.g., 2-methylimidazolate, benzimidazolate) (See Fig. 1) [11]. The framework of ZIFs can be represented as: T(Im)2, where Im = imidazolate and its derivatives and T = tetrahedrally coordinated metal ion. This is similar to the (Al)SiO2 frameworks of (alumino) silicate zeolites. In particular, the T-Im-T angle of 145° is close to the Si-O-Si angle typically found in zeolites [12,13]. These solid materials are highly porous and have the ability to selectively adsorb and release molecules, as well as to display an impressive range of structural diversity and tunability [14]. As a result, they are being explored for a range of applications, including preservation, encapsulation, sensing, catalysis, gas separation, and gas storage [12,[15], [16], [17]]. It has been reported that zeolites and ZIFs have the potential for selective adsorption and desorption of bioactive agents [18,19]. Due to differences in their porosities, ZIFs have higher surface areas (> 1000 m2 g−1) than zeolites (<1000 m2/g). Moreover, zeolites do not allow as close control over the size, shape, and surface chemistry of the pores. In contrast, zeolites suffer from problems such as non-uniform structure, irregular pores, and lack of clear structure-property relationships [8,10]. Typically, ZIFs also have a relatively high stability over a range of environmental conditions.

One notable advantage of ZIFs lies in their exceptional thermal and chemical stability, rendering them suitable for application in harsh environments [20,21]. Unlike traditional zeolites, which often have limited stability under acid or alkaline conditions, ZIFs exhibit robustness over a wide range of pH values and are resistant to high moisture levels and elevated temperatures [21,22]. This high stability would be an advantage for their utilization as additives in food packaging applications. ZIFs can be synthesized with tailored pore sizes and surface chemistries, enabling the selective adsorption and release of guest molecules [23]. This property has led to their exploration to encapsulate, protect, and release active compounds in packaging applications [24,25]. In particular, the tunable properties of ZIFs provides the ability to control the release profile or target the delivery of active compounds [18]. ZIFs can be modified using different substances to improve their functionality [23]. For example, modification with amino acids or peptides has been shown to enhance the encapsulation and release kinetics of bioactive agents [26]. The high surface area and porosity of ZIFs also make them suitable for applications in sensing and detection, as well as catalysts for a range of chemical reactions, as they can interact with specific target molecules, leading to enhanced sensitivity and selectivity [27,28]. ZIFs have already been used as sensors for specific gases, ions, contaminants, and biomolecules [11,14]. By adding specific receptors or ligands to ZIFs, they can selectively interact with target substances, causing changes in their optical or electrical properties [13]. This enables the creation of highly sensitive and selective sensors. For instance, ZIFs combined with metal ions have been successfully employed to detect harmful gasses like ammonia and sulfur dioxide [27]. ZIFs also have other desirable characteristics, such as simple synthesis methods and tunable dimensions and pore sizes. At present, however, there is a lack of knowledge about the potential applications of ZIFs in food packaging applications. A diverse range of studies have shown that incorporation of ZIFs can lead to significant improvements in the optical, mechanical, barrier, sustainability, thermal, antioxidant, and antimicrobial properties of packaging materials. In addition, they have shown that ZIFs can be used as carriers to encapsulate, protect, and control the release of bioactive compounds [[29], [30], [31]]. Consequently, there is a need for a review article that summarizes previous studies on the design and application of ZIFs in food packaging materials, and highlights where future research is required.

This article therefore discusses the synthesis, properties, and potential applications of ZIFs in smart and active packaging films, as well as their current limitations. Moreover, the impact of ZIFs on the physical, mechanical, barrier, preservative, and gas scavenging properties of packaging materials is also discussed. The safety aspects of ZIFs in food packaging applications are also highlighted, and potential areas for future research are presented.