Molecularly Imprinted Polymer-Supported Ceramic Catalysts for Environmental Applications: A Comprehensive Review

Abstract

Molecularly imprinted polymers (MIPs) are synthetic polymers designed to exhibit selective recognition and binding capabilities toward target molecules and have been widely combined with advanced ceramic-based materials toward better performance in many catalytic applications of interest and beyond. What sets MIPs apart is their molecularly imprinted cavities, which are formed during polymerization in the presence of a template molecule. Upon template removal, these cavities retain the shape, size, and chemical functionality of the template molecule, allowing for highly specific recognition and binding of target molecules. In recent years, there has been a growing interest in leveraging these molecularly imprinted cavities not only for molecular recognition and sensing but also as catalytic sites and supports. Complementary to experimental studies, density functional theory (DFT) calculations are increasingly used to elucidate the molecular interactions, catalytic mechanisms, and optimize the design of MIP–ceramic catalysts. This review aims to provide a comprehensive overview of the current state of research on advanced ceramic-based catalysts supported by MIPs for environmental applications. Additionally, the review will discuss challenges and future directions in the field, focusing on enhancing the catalytic efficiency, stability, and scalability of MIP-based ceramic catalysts. By exploring these aspects, this review seeks to illustrate the promising role of MIP-modified ceramic materials in advancing the field of catalysis and catalytic supports.

1. Introduction

Catalysis is, of course, a fundamental concept in chemistry that involves accelerating chemical reactions using substances known as catalysts. Catalysts are not consumed during reactions and can be repeatedly used, lowering the activation energy barrier. This enables efficient and sustainable chemical processes, yielding both economic and environmental benefits [1,2]. Figure 1B presents an illustrative diagram highlighting these diverse applications, demonstrating how catalysis interacts with various areas of study, driving significant advancements in each. As we know, catalysis can be classified into several types, including homogeneous, heterogeneous, and enzymatic (see Figure 1A).

Owing to the widespread application of heterogeneous catalysis in industry, this review will focus primarily on this type of catalyst. In this type of catalysis, the catalyst exists in a different phase than the reactants; a typical example involves a solid catalyst interacting with liquid- or gas-phase reactants, facilitating its separation and reuse [1,2]. The performance of heterogeneous catalysts often depends on the nature of the catalytic support, which provides a surface for the active catalytic sites, thereby influencing activity, selectivity, and stability [1,2,3,4,5,6,7]. Figure 1C shows in simplified form a generic example of a supported heterogeneous catalyst. Functioning as a structural base for active catalyst dispersion, catalytic ceramic supports are essential for improving catalyst efficiency and durability, making them essential for industrial applications where high catalytic activity and longevity are required [3]. These ceramic materials, commonly porous substances such as alumina, silica, or zeolites, are designed to maximize surface area and optimize the distribution of active sites and accessibility to reactants [4,5]. Hence, catalytic ceramic supports are indispensable in heterogeneous catalysis for boosting catalyst performance [6,7].

In the pursuit of sustainable technologies, the design of efficient and selective catalysts is paramount. An advanced strategy in this area features the combination of molecularly imprinted polymers (MIPs) with ceramic-based materials, yielding hybrid systems with tailored molecular recognition capabilities and improved durability, offering significant potential for sustainable catalytic applications [8,9,10,11,12]. MIPs showcase remarkable versatility, functioning as enzymatic catalysts by mimicking the active sites of natural enzymes, participating in catalytic processes of chiral molecules, and playing crucial roles in environmental chemistry [11,12,13,14]. In environmental applications, MIPs selectively recognize and bind target molecules, thereby allowing the selective adsorption and recovery of valuable contaminants [15] or the adsorption and further degradation by (photo)catalytic processes of specific toxicants [15,16,17]. Recent developments have demonstrated that ceramic-supported MIPs are highly effective in removing organic pollutants, enabling selective adsorption, photodegradation, and even sensor-based detection of environmentally hazardous substances. These hybrid systems have shown exceptional potential for use in water purification, air quality monitoring, and the degradation of persistent contaminants, thanks to their tunable selectivity, high surface area, and stability under operational conditions. Additionally, computational modeling has begun to play a key role in the rational design of these systems, allowing prediction and optimization of their structure and catalytic behavior in environmentally relevant contexts. In the degradation of compounds, MIPs can function as catalysts, sorbents, or sensor components [18,19,20]. Their ability to mimic the natural recognition properties of biological receptors makes MIPs highly valuable in several catalytic applications [21,22]. The prospect of designing novel catalysts using computational methods has long been a “Holy Grail” in the field [23]. While computational tools have advanced significantly, allowing for calculations that were once highly time-consuming to be performed rapidly, the de novo design of catalysts remains a formidable challenge [24,25,26].

Therefore, this review article aims to address the main characteristics of advanced ceramic-based catalysts supported by MIPs, focusing on their structural properties, performance metrics, and potential applications in various chemical processes of environmental interest. It will also cover computational methodologies, particularly those based on Density Functional Theory (DFT), used in order to investigate the structural, electronic, and catalytic properties of these novel catalytic systems. Additionally, the present work aims to delve into the advantages and limitations of MIP/ceramic catalytic systems compared to traditional catalysts, providing a comprehensive overview of current research trends and future directions in this field.

2. Fundamentals of Heterogeneous Catalysis

Chemical reactions underpin societal development, with advances in chemical technologies yielding essential products, such as pharmaceuticals, vaccines, fertilizers, fuels, food additives, and so on [27]. The efficiency gains driving modern scientific and technological progress are particularly linked to catalytic processes. Catalysts are defined as substances that accelerate chemical reactions without changing the standard Gibbs free energy (∆G_r°). As we know, in a chemical reaction, the activation energy is the energy barrier that reactants must overcome to form products, and it is reduced by catalysts. This reduction allows a greater proportion of reactant molecules to attain the transition state at a given temperature, thereby increasing the reaction rate [28]. Notably, catalysis contributes to over 35% of the global GDP, and it is a key component in approximately 80% of all manufactured goods [29], owing to the fact that catalysts accelerate reactions, reducing energy consumption, and increasing the yield of desired products, thereby enabling the industrial-scale production of critical materials [30,31,32].

Importantly, while catalysts speed up the attainment of equilibrium, they do not alter the position of the equilibrium itself. Thus, the ΔG_r is a thermodynamic parameter that indicates the difference in free energy between reactants and products under standard conditions, thereby determining reaction spontaneity (ΔG° < 0) or non-spontaneity (ΔG° > 0). Given that catalysts do not alter the intrinsic energy states of the reactants or products, the overall ΔG° remains constant [33]. Consequently, while catalysts enhance the reaction rate by lowering the activation energy, they do not affect the thermodynamic favorability of the reaction [34]. Therefore, catalysis represents a highly relevant and multidisciplinary field, finds applications in chemical synthesis, materials engineering, surface science, and physical chemistry. Its versatility enables the optimization of chemical reactions in numerous contexts, leading to innovative and efficient solutions.

Catalysts can be classified as homogeneous and heterogeneous, where, in the first type of catalysis, the reactants and the catalyst are in the same phase; in its turn for heterogeneous catalysis, the reactants and the catalyst must be in different phases [35]. For instance, in biological systems, enzymes function as natural homogeneous catalysts that facilitate vital biochemical reactions necessary for life, operating under the same principle of lowering activation energy without altering ΔG° [33]. Therefore, catalysts are important because they allow reactions to have an alternative mechanism, faster than the one that occurs in their absence. Although the catalyst participates in the mechanism reaction, at the end of the reaction cycle, it can be regenerated and used again in the same or some other chemical process [36,37]. In principle, the catalyst would not be consumed at the end of a catalytic cycle; however, undesirable parallel reactions, the presence of ‘catalytic poisons’, or bad operating conditions can lead to loss of catalytic activity [38]. In this review article, we will emphasize heterogeneous catalysts.

Heterogeneous catalysis is pivotal in many industrial processes, producing various chemicals, fuels, and materials, while enhancing reaction rates and selectivity [39,40]. In this way, there has been a search for more specific, reusable catalysts that generate high-quality products without the need for so much purification; hence, to meet these requirements, the use of heterogeneous catalysts is pursued. Historically, the first heterogeneous catalytic reaction was studied by Priestley in 1778 when attempting to dehydrate ethanol by active clays. Later, in 1796, Van Marum was the first to use metallic catalysts for the dehydrogenation of ethanol. In 1813, Thenard discovered that ammonia decomposes into nitrogen and hydrogen when passed over various burning metals. In 1823, Dulong found that the activity of different metals such as iron, copper, silver, gold, and platinum for decomposing ammonia decreased in that order. Meanwhile, in 1814, Kirchoff reported that acids facilitate the hydrolysis of starch to glucose. In 1817, H. Davy and E. Davy noted hydrogen oxidation by air over platinum, and Faraday studied why platinum facilitates oxidation reactions [41,42]. With these initial researchers, heterogeneous catalysis evolved into a crucial aspect of the chemical industry. This is because catalysts, usually solid, are at a different phase than reactants and products, thereby making their separation more cost-effective. Key characteristics of an effective catalyst include activity, selectivity, reproducibility, thermal and mechanical stability, and ease of regeneration. Additionally, catalyst activity is influenced by the nature, quantity, strength, and spatial arrangement of the chemical bonds formed temporarily between the reactants and the catalyst surface, which depends on the solid catalyst’s composition, structure, and morphology [35,43]. As we know, the catalyst activity is highly dependent on the active component(s) included in its surface structure and composition. In the specific case of heterogeneous catalysis, catalyst activity is composed of a main active component, the proportion of which exceeds that of other components and secondary components, which are included to improve the catalyst’s activity, called additives or, sometimes, promoters or modifiers. The promoter is a substance that does not have catalytic properties by itself; however, when added to the catalyst, it improves its properties, for instance, by stabilizing the catalyst structure or by modifying the chemical properties of the catalyst surface [35,44]. Heterogeneous systems offer several advantages compared to conventional homogeneous catalysis, such as the following:

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Solid catalysts can be easily separated from the reaction products, and this is very important, allowing the recovery of the catalyst for future reuse in the reaction medium;

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Separation simplifies and reduces product purification washing steps;

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In the same way that the volume of water for washing and purifying the organic phase is reduced, it is a very important advantage from an environmental point of view due to reduced wastewater discharges;

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The possibility of using raw materials of lower quality and consequently lower cost.

Recent advancements in heterogeneous catalysis have focused on increasing efficiency, selectivity, and durability. Tailored synthesis of ceramic materials facilitates the creation of catalysts with optimized properties. Additionally, sustainable and green catalysis is an emerging area, aiming to create environmentally friendly catalytic processes that reduce waste and energy consumption [45,46]. Heterogeneous catalysts are crucial in many industrial applications, such as the production of high-purity biodiesel and glycerol [47,48], degradation of environmental contaminants [49], and catalytic support [50], among many other uses.

Sivasamy [39] categorizes heterogeneous catalysts into seven groups: metal oxides, mixed and doped metal oxides, supported catalysts, zeolites, lamellar double hydroxides, organic bases, and anionic resins. Supported catalysts, which disperse active catalytic materials onto high surface area solid supports, are of great industrial interest [51]. These supports are chosen for their porosity, mechanical resistance, and ability to prevent active metal particle sintering, which can be catalytically active or inactive [52]. Nanometric metal particles dispersed on these supports (such as alumina, silica, and/or zeolites) enhance catalytic efficiency, reduce costs through lower metal usage, offer adjustable selectivity, and enable catalyst reuse [53]. Preparation methods, including impregnation, co-precipitation, and sol–gel processes, aim to achieve uniform active phase dispersion and controlled particle size [54,55]. Impregnation, for instance, involves soaking the support in a solution containing the catalytic material, followed by drying and calcination to fix the active species onto the support [35,56]. Owing to their high reactivity, selectivity, and stability, supported metal catalysts are essential in fuel, chemical commodities, and automotive industries [57]. Before the 1970s, non-transition metal oxides (e.g., Al₂O₃, SiO₂) were commonly used as supports, primarily acting as high surface area, thermally stable materials for dispersing metal nanoparticles and maximizing active sites [4,58,59] Moreover, earlier, as in the 1970s, researchers observed that when metallic nanoparticles are supported on transition metal oxides (TiO₂, Nb₂O₅, CeO₂, etc.), they exhibit tunable chemical and catalytic behavior [59,60,61]. Indeed, developing advanced supported catalysts is a dynamic field of research, with ongoing efforts to design materials with enhanced activity, selectivity, and durability. Innovations such as the use of nanostructured supports, bimetallic catalysts, and the incorporation of promoters and inhibitors are pushing the boundaries of what can be achieved with supported catalysts. These advancements promise more efficient and sustainable industrial processes, ultimately contributing to cleaner and more energy-efficient development. Another type of catalytic support that is currently gaining a lot of attention is the so-called MIPs—Molecular Imprinted Polymers, so in the following topics, this review paper will focus on defining and showing their characteristics and applications as catalytic support [62,63].

3. Overview of Molecularly Imprinted Polymers as Catalysts and Support for Catalysts

3.1. General Aspects

MIPs are cross-linked synthetic polymers engineered with specific recognition sites, created using a target molecule as a template. This process yields high selectivity and affinity for the target, enabling a “lock and key” binding mechanism analogous to natural antibody–antigen systems. During MIP synthesis, the template forms a stable active complex with the functional monomer in a porogenic solvent containing initiators and a cross-link. This complex is then fixed within the rigid, porous polymer matrix via polymerization [64,65]. Initially, the monomers are spatially arranged around a template molecule. Their positions are fixed through polymerization, resulting in a three-dimensional polymer matrix containing both macropores and microcavities. By washing this polymer matrix with specific solvents, the template molecule is removed, unveiling binding sites that are complementary in shape to the template. Consequently, the polymer can thus recognize and selectively bind template molecules dispersed, for instance, in an aqueous matrix. Figure 2 illustrates the process of obtaining MIPs. MIP’s binding sites vary in characteristics depending on the interactions established during polymerization. The classification of molecular imprinting (typically covalent or non-covalent) depends on the nature of these monomer–template interactions.

The need to extract the target molecule post-use hinders MIP application in sensors, because residual target molecules can interfere with subsequent detection. However, despite this challenge, MIPs have successfully been commercialized. For instance, MIP Technologies, a Swedish company responsible for producing non-biological affinity reagents targeting small molecules, proteins, viruses, and other substances. Another prominent use of MIPs is in Sigma-Aldrich’s SupelMIP line, which offers MIP-based extraction materials for solid-phase extraction (SPE) columns [64,66].

3.2. Types of Monomers

As already mentioned, the monomers are small molecules that can undergo polymerization, thereby contributing to the constitutional unit of the essential structure of macromolecules [67]. The choice of monomers is crucial for the performance of MIPs, and there are basically four types of monomers: those that have acidic, basic, neutral, and cross-linking characteristics. The acidic monomers typically contain functional groups that can release protons (H⁺) in aqueous solutions, hence making them acidic. In contrast, the basic monomers contain functional groups that can accept protons (H⁺) in aqueous solutions, making them basic, whereas the neutral monomers do not significantly alter the pH of the solution. The last type of monomer (cross-linking) has functional groups that can form covalent bonds with other monomers during polymerization, thereby creating a three-dimensional network within the polymer.

Table 1. Monomers used to obtain MIPs.

Characteristics	Monomer Chemical Structure	Name	Advantages/ Disadvantages	Reference
Acidic		acrylic acid (AA)	Strong hydrogen bonding capacity; may be unstable under extreme pH conditions.	[68]
		p-vinylbenzoic acid (VBA)	High selectivity; limited solubility may restrict applications.	[68]
		2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA)	Excellent hydrophilicity and thermal stability; excess may interfere with polymerization.	[69]
Basic		2-vinylpyridine (2-VP)	Strong interaction with acidic templates; strong odor and toxicity are drawbacks.	[68]
		N,N-diethylaminoethyl methacrylate (DEAEM)	Good structural flexibility; sensitive to oxidation.	[70]
		Allylamine	High reactivity and affinity for acidic groups; unstable under light and oxygen exposure.	[71]
Neutral		methyl methacrylate (MMA)	High stability and easy polymerization; low affinity for specific targets.	[72]
		4-ethylstyrene	Stable and non-polar, suitable for hydrophobic targets; limited interaction functionality	[73]
		methacrylamide	Good solvent compatibility; lower reactivity compared to other monomers.	[74]
Cross-linking		ethylene glycol dimethacrylate (EGDMA)	Widely used, ensures rigidity and structural stability; may limit analyte diffusion.	[75]
		N,N′ -1,3-phenylenebis(2- methyl-2-propenamide) (PDBMP)	Rigid structure, ideal for selective recognition; more complex synthesis.	[76]
		pentaerythritol triacrylate (PETRA)	High cross-linking density and stability; may reduce accessibility to active sites.	[77]

shows some examples of these four classes of monomers.

The careful selection of monomers for the fabrication of MIPs is crucial for ensuring the effectiveness and specificity of the final polymer. Firstly, the affinity between the monomers and the template molecule is essential. The monomers must interact strongly and specifically with the template molecule through non-covalent interactions, such as hydrogen bonding, π–π interactions, or ionic interactions [78]. Besides affinity, the compatibility of the monomers with the chosen polymerization method is another crucial criterion. Different polymerization methods, such as bulk, precipitation, or emulsion polymerization, require specific characteristics of the monomers to ensure efficient polymerization and the formation of a stable polymer matrix. In addition, the stability of the resulting polymer is also a determining factor in the selection of monomers. The monomers must be chosen to confer the necessary resistance to the final MIP to withstand the conditions of use, which may include changes in pH, temperature, and the presence of aggressive solvents. Cross-linking monomers like ethylene glycol dimethacrylate (EGDMA), divinylbenzene (DVB), and trimethylolpropane trimethacrylate (TRIM) are commonly used for providing structural integrity and stability. Another important criterion when choosing monomers is their solubility, since the monomers should be soluble in the chosen porogenic solvent to ensure uniform polymerization. Porogenic solvents like toluene, acetonitrile, dimethyl sulfoxide (DMSO), and methanol play a critical role in controlling the morphology and porosity of the final MIP, influencing its performance in recognizing and binding the target molecule. Thus, the careful monomer selection process can guarantee the creation of MIPs with high specificity, stability, and efficacy in the intended applications [79,80].

MIPs have several advantages compared to other design materials. MIPs have extremely high chemical and thermal stabilities, and high affinity and specificity for target analytes. MIPs can be reused, are stable upon storage, and maintain their recognition capacity for many years [77,81]. The synthesis of MIPs presents several challenges, particularly when aiming to create efficient MIPs without prior knowledge of the ideal solvent and monomer. The choice of solvent and monomer is crucial for the efficiency of the molecular imprinting process. The solvent plays a fundamental role in MIP formation, influencing the solubility of the components and the stability of the interactions between the functional monomer and the target molecule. Without prior knowledge of the ideal solvent, issues such as inadequate solubility can arise, leading to precipitation or insufficient formation of the pre-polymerization complex. Additionally, non-ideal solvents can interfere with the specific interactions between the monomer and the target molecule, resulting in less specific or non-functional binding sites. Certain solvents can also affect the polymerization rate and the final structure of the polymer, negatively impacting the efficiency of the MIP. Additionally, non-ideal solvents can interfere with the specific interactions between the monomer and the target molecule, resulting in less specific or non-functional binding sites. Certain solvents can also affect the polymerization rate and the final structure of the polymer, negatively impacting the efficiency of the MIP. The lack of knowledge about the ideal solvent and monomer necessitates extensive experimental optimization. Computational chemistry offers a powerful approach to overcoming the challenges in synthesizing MIPs without prior knowledge of the ideal solvent and monomer. By utilizing simulations and computational modeling, it is possible to predict and optimize the interactions between monomers, target molecules, and solvents, thereby saving time and resources that would otherwise be spent on traditional experiments [82,83]. With this in mind, computational chemistry methods can be employed in the study of MIPs; in fact, this is a field that has stood out in recent years due to its ability to predict the structural and functional properties of these materials efficiently and accurately.

3.3. MIPs as Efficient Catalysts

One area where MIPs have gained significant attention is catalysis, owing to their unique and specific properties. MIPs can indeed be viewed as efficient catalytic materials, although they differ in some key aspects from traditional catalysts. They have a series of advantages, as MIPs can be designed to have high specificity for certain target molecules due to their molecular recognition capabilities [8], which can be advantageous in catalysis for allowing selective reactions. Furthermore, MIPs are very stable under a wide range of conditions, including extreme pH and temperature values, making them robust catalysts for various applications. In addition, MIPs are often reusable, which is a significant advantage compared to some traditional catalysts, which can degrade over time or lose activity [50,62,84].

Many studies use MIPs as catalysts. Thus, MIPs can be synthesized to imitate enzymes and other biological molecules, expanding their catalytic potential beyond traditional catalytic materials. Enzymes are natural biocatalysts responsible for catalyzing various biochemical reactions in living organisms. As in other proteins, natural enzymes are macromolecules composed of long chains of amino acid residues with added cofactors and other post-translational modifications. Enzymatic catalysis usually occurs in a small part of the enzyme molecule (known as the active site) with high selectivity and rate. The tight binding of a substrate to the functional groups in an enzyme facilitates catalysis through proximity effects. Although natural enzymes can catalyze reactions with high regioselectivity and stereoselectivity under mild biological conditions, they are often costly to obtain and unstable in practical applications. Consequently, replacing biomolecular enzymes with more durable synthetic compounds or materials has become an appealing endeavor to meet the diverse requirements of catalytic reactions [62,85,86]. For instance, carboxypeptidase A (CPA) has been one of the most studied enzyme compounds in the analytical field of MIPs.

In the reaction illustrated in Figure 3 [87,88], molecularly imprinted nanogels containing a proline derivative were prepared for the first time. These nanogels exhibit high catalytic activity, turnover, and enantioselectivity in the cross-aldol reaction between cetone and 4-nitrobenzaldehyde, following the enamine-based mechanism typical of aldolase type I enzymes. Furthermore, a novel approach for active-site titration was developed, utilizing the reaction between a catalyst and a substrate to produce a readily detectable product. This method enabled the precise calculation of catalytic parameters, providing valuable insights into the composition of the polymer [89].

Pioneering work on MIPs [88] focused on printing acrylamide-based nanogels using a covalent method that involves the formation of a reversible enaminone, resulting in nanogel preparations with exceptional catalytic activity, turnover, and enantioselectivity. Additionally, recent studies by Mukhopadhyay et al. [90] demonstrated that nanogels can be effectively utilized as drug delivery systems, highlighting their versatility and potential in biomedical applications, which complements and expands upon the initial MIP studies.

Additionally, the strategic design of the model molecule enables the creation of catalysts tailored to produce a variety of molecules that are otherwise challenging to synthesize. Furthermore, recent research has focused on various applications of MIPs in catalysis. One area of interest is the development of MIP-based enzyme mimics, often called “artificial enzymes” or “nanozymes”, designed to catalyze specific biochemical reactions with high efficiency. Studies have demonstrated MIPs mimicking peroxidase activity for use in biosensing and environmental applications [91,92]. Another promising field is photocatalysis, where MIP-based photocatalysts are tailored to recognize and bind specific substrates under light irradiation, enhancing reaction rates and product specificity, useful in pollutant degradation and fine chemical synthesis [93]. Moreover, MIPs are being utilized in asymmetric catalysis to produce chiral compounds, as the molecular imprinting process creates chiral cavities in the polymer matrix, aiding pharmaceutical synthesis [93,94]. In green chemistry, MIPs serve as catalysts that facilitate reactions under mild conditions, reducing the need for harsh chemicals and extreme conditions [95]. Industrial applications also benefit from MIP technology, as these polymers offer a sustainable and efficient approach to catalysis, promoting environmentally friendly synthesis pathways [96].

Table 2. Overview of selected MIPs highlighting their key features, applications, and references to relevant studies.

MIP	Key Features	Application	References
Nanogels with Proline Derivatives	-High catalytic activity -High enantioselectivity -Enamine-based mechanism typical of aldolase I enzymes	Cross-aldol reaction between acetone and 4-nitrobenzaldehyde	[87,88]
Acrylamide-Based MIPs	-Covalent method with reversible enaminones -High stability and catalytic activity	Catalysis of organic reactions with high selectivity	[89]
Enzyme-Mimicking MIPs	-“Nanozymes” mimicking natural enzymes -High efficiency in biochemical reactions	Biosensors, environmental applications, peroxidase for pollutant degradation	[90,91]
MIP Photocatalysts	-Molecular recognition under light irradiation -High reaction rates and specificity	Pollutant degradation and fine chemical synthesis	[92]
MIPs for Asymmetric Catalysis	-Chiral cavities in the polymer matrix -Synthesis of chiral compounds with high selectivity	Pharmaceutical compound production	[93,94]
MIPs in Green Chemistry	-Facilitation of reactions under mild conditions -Reduction in the use of harsh reagents	Sustainable and environmentally friendly synthesis	[95]
MIPs in Industrial Applications	-Sustainable methods -High efficiency and reusability	Large-scale catalysis and environmentally friendly synthesis pathways	[96,97]
Nanogels for Drug Delivery	-High versatility -Biomedical compatibility	Controlled drug delivery systems	[98]

provides an overview of the best MIPs, showcasing their unique features, diverse applications, and supporting references.

In brief, the continued development and varied uses of MIPs—ranging from efficient catalytic supports to roles in drug delivery, biosensing, and green chemistry—underscore their transformative potential for providing innovative and sustainable solutions across multiple fields and advanced systems.

3.4. MIPs as Efficient Catalytic Supports

Industrial chemical processes rely heavily on catalysis, driving continuous efforts to develop new catalysts and improve existing systems according to green chemistry principles: achieving high yield and selectivity under mild conditions, often minimizing or using environmentally friendly solvents [43,50,99]. MIPs serve as efficient catalytic supports that align with these goals. MIPs can be used to immobilize enzymes or other catalytic agents, facilitating catalyst separation and reuse, which is particularly useful in sustainable industrial applications [33,98]. Furthermore, the use of MIPs as a catalytic support can be important for the degradation of pollutant molecules, enabling their use for water and wastewater treatment [84].

Pollutant removal from various matrices and their degradation are of increasing concern as emerging pollutants are discharged into water treatment plants and are only partially removed through adsorption and biochemical degradation; complete elimination and mineralization are not achieved with conventional WTPs because they are not designed for metabolite degradation [18,100]. In this context, MIPs present a viable alternative due to their ability to selectively adsorb molecules of interest, which can then be further degraded by catalytic reactions, thereby playing a crucial role in water and wastewater treatment [101,102,103,104].

These polymers are synthetic three-dimensional materials with specific pores and cavities created through molecular imprinting, which allows them to retain specific molecules. Furthermore, they can be synthesized using a template analyte to impart a specific shape, arrangement, orientation, and union sites, and after the template’s removal, the cavities remain ready to be re-occupied by the analytes or similar compounds. MIPs offer several advantages, including reversible adsorption and desorption, thermal, mechanical, and chemical stability, low cost, and ease of preparation. Berrones [84] tested the use of TiO₂-based MIPs as catalytic support for the oxidation and degradation of 4-nonylphenol compounds, aligning with green chemistry principles by reducing the need for hazardous reagents and conditions, thus enabling more sustainable chemical processes.

Although MIPs have demonstrated significant potential in several applications, including as catalytic supports, they also have several limitations [103], which include (i) a complete removal of the template molecule from the polymeric matrix without leaving residues is a major challenge (any residual template can interfere with the catalytic process and reduce the MIP efficiency); (ii) the synthesis of MIPs with high specificity and activity can be complex and time-consuming; (iii) MIPs may have limited mechanical and chemical stability under certain conditions, such as extreme pH or temperature (which may restrict their practical applications in catalysis); and (iv) the usually high costs associated with MIP synthesis, especially the ones with high specificity and desired physical properties, may surpass that of traditional catalytic supports, thereby limiting MIP applications. Despite these limitations, ongoing research and development in the field of MIPs aim to address these challenges and improve their performance and applicability as catalytic supports [105,106]. The adsorption performance of MIPs depends on various factors, including the functional monomer, porogenic solvent, and catalyst.

Table 3. Performance of MIPs with Different Functional Monomers and Porogenic Solvents.

Functional Monomer	Molecule Template	Porogenic Solvent	Catalyst	BET (m2/g)	Qmax (mg/g)	Ref.
Methacrylate Acid (MMA)	17-β-estradiol	Acetonitrile	---	128	42	[107]
	Nicotine	Methylene chloride	---	97	55	[108]
	3-Methylindole	Toluene	Fe3O4	112	64	[109]
	Oxytetracycline	Water	Fe3O4	85	37	[110]
	Glutathione	Acetonitrile/toluene	---	143	58	[111]
	Dienoestrol	Acetonitrile	Fe3O4@SiO2	134	49	[112]
Acrylic acid	Red Remazol	Dimetilformamida	Fe3O4	120	63	[113]
	Methanoic acid	Acetonitrile/toluene	Fe3O4@SiO2	110	51	[114]
	Aristolochic acid	Dimethylformamide	---	115	56	[115]
4-VP	Ibuprofen	Acetonitrile	---	120	50	[116]
	Caffeic acid	Dimethylformide	---	130	60	[117]
	methocarbamol	Tetrahydrofuran	---	110	47	[118]
	4-nitrophenol	Acetonitrile	Fe3O4	140	55	[119]

presents data on MIPs synthesized with different functional monomers, molecular templates, porogenic solvents, and catalysts.

The BET surface area and adsorption capacity (Q_max) vary significantly, indicating that the choice of porogenic solvent and catalyst plays a crucial role in determining the material’s properties. Methacrylate Acid (MMA) and Acrylic Acid are the main monomers used, with one case of 4-Vinylpyridine (4-VP). The BET values range from 85 mg²/g to 143 mg²/g, while Q_max varies between 37 mg/g and 60 mg/g, showing that higher porosity does not always correlate with higher adsorption. This apparent lack of correlation can be attributed to the fact that the adsorption capacity in MIPs is primarily determined by the number, specificity, and accessibility of the imprinted binding sites rather than the overall surface area. In other words, a polymer with a lower surface area but well-defined, high-affinity binding cavities can outperform one with a larger surface area but poorly formed or less accessible recognition sites. The use of Fe₂O₃ and Fe₂O₃@SiO₂ as catalysts in some cases suggests potential modifications in surface properties that could influence adsorption performance. These findings highlight the importance of optimizing synthesis parameters to enhance the efficiency of MIPs for specific applications. As seen before, MIPs as catalytic supports offer high selectivity, enhanced catalytic activity, stability, and tunable properties, making them highly efficient for a variety of catalytic processes. Future research will likely focus on overcoming current limitations and expanding their applications in different fields. The following

Table 4. Overview of MIPs as Efficient Catalytic Supports.

Aspects	Details
Properties of MIPs	High specificity, stability under extreme conditions (pH, temperature), reusability, and robustness for various applications.
Advantages over Enzymes	Replace natural enzymes (expensive and unstable), mimicking their catalytic function with high regioselectivity and stereoselectivity.
Practical Example	Aldol reaction between acetone and 4-nitrobenzaldehyde catalyzed by nanogels containing proline derivatives, with high catalytic activity and enantioselectivity.
Recent Innovations	-Active-site titration method for precise calculation of catalytic parameters. -Molecular imprinting based on acrylamide for nanogels with superior catalytic activity.
Emerging Applications	-Enzymatic mimicking (“nanozymes”). -Photocatalysis for pollutant degradation. -Asymmetric catalysis for the synthesis of chiral compounds.
Impact on Green Chemistry	Reactions under milder conditions, reduction in harsh chemicals, and more sustainable syntheses for industrial and pharmaceutical applications.
Future Perspectives	Integration into biosensors, environmental catalysis, and the development of efficient drug delivery systems.

provides a summary of MIPs as efficient catalytic supports.

Furthermore, due to their high selectivity and molecular recognition capacity, MIPs have been widely studied in several areas, standing out especially in environmental applications, where their potential is explored for the detection, removal, and monitoring of pollutants, as will be shown below.

4. Overview of Advanced Ceramic Materials as Catalysts

Advanced ceramic materials, broadly defined as inorganic, non-metallic solids prepared by heating and subsequently cooling, encompass a wide range of compositions, including metal oxides, carbides, borides, nitrides, and composites [120,121]. These materials have gained significant notoriety due to their straightforward synthesis and the properties that depend on size, composition, structure, and morphology, as well as imperfections in these parameters [122,123,124,125]. Notably, ceramic-based catalysts offer notable advantages in terms of durability, selectivity, and reusability compared to traditional metal-based catalysts. This Section provides a comprehensive overview of ceramic catalysts, emphasizing their structural characteristics, synthesis techniques, and broad applications across industries such as energy production, environmental remediation, and chemical manufacturing.

A key strength of ceramic catalysts lies in their tunable porosity and surface functionalities, which can be precisely engineered to boost both catalytic activity and selectivity. This inherent tunability makes them highly adaptable to the demands of complex reaction environments [120,121,122,123,124,125,126,127]. Furthermore, recent advances in nanostructuring and the development of ceramic-based composites have broadened their potential. This enables synergistic effects with other materials, paving the way for their incorporation into advanced catalytic platforms [125]. Beyond their intrinsic properties, it is well-known that the method of synthesis plays a critical role in determining the final performance of ceramic catalysts. Consequently, a diverse range of synthetic approaches has been widely developed to tailor the composition, structure, size, morphology, and porosity of ceramic catalysts [126,127,128,129,130,131]. Among the most widely employed methods are sol–gel processing, hydrothermal synthesis, and solid-state reactions. Sol-gel processing involves the hydrolysis of metal alkoxides or salts to form a gel-like precursor, which is subsequently dried and calcined to obtain the ceramic material. This method is well-regarded for producing high-purity ceramics with controlled microstructures. Hydrothermal synthesis, on the other hand, relies on chemical reactions conducted in aqueous solutions under high temperature and pressure, producing ceramics with uniform particle size and high crystallinity. Solid-state reactions involve the thermal treatment of mixed metal oxides or carbonates, leading to the formation of the desired ceramic phase. Each of these methods offers specific advantages, allowing the fabrication of customized ceramic catalysts to meet the demands of various catalytic systems [132,133].

Ceramic catalysts have found widespread use in industrial processes ranging from energy production to pollution control [120,121,122,123,124,125,126,127,128,129,130,131,132,133,134]. One of the most prominent applications is in the automotive sector, where ceramic catalysts are integral to catalytic converters that reduce harmful emissions. Their ability to withstand high temperatures and corrosive environments makes them ideal for operation within vehicle exhaust systems. In the energy sector, ceramic catalysts are utilized in hydrogen production and fuel cells, where their robustness and capacity to support metal nanoparticles enhance overall efficiency. Their role in biofuel production is also gaining momentum, as they facilitate the conversion of biomass into energy with high efficiency and lower environmental impact. Furthermore, ceramic catalysts are essential in environmental remediation efforts, particularly in treating industrial waste streams. Their chemical and thermal stability enables them to drive reactions that break down hazardous pollutants into less toxic byproducts. Additionally, ceramic materials are employed in the synthesis of fine chemicals and in petrochemical processes, where they offer a cost-effective, scalable, and efficient catalytic platform [134].

Despite their many advantages, ceramic catalysts may face limitations in terms of structural flexibility and functional group diversity. In such contexts, materials like MIPs can offer more tailored molecular recognition capabilities. A comparative analysis of ceramic catalysts and MIPs underscores the need to match material properties with the specific requirements of the catalytic process in question.

5. Computational Catalyst Design

Computational chemistry is a branch that uses computer simulations to solve chemical problems, thereby bridging the gap between theoretical concepts and practical applications in chemical sciences [82,83]. It employs theoretical methods and mathematical models to study the structures, properties, and behaviors of molecules and materials. This field is crucial for drug and materials design, engineering, and developing new technologies. Theoretical methods are essential for understanding molecular behavior, predicting chemical reactions, and designing new materials and drugs. Thus, they allow for the rational design of imprinting templates by predicting the most suitable functional monomers and their optimal configurations, which is particularly relevant for developing advanced materials, including ceramics with tailored properties.

Researchers can simulate the target molecule–potential monomer interactions through computational chemistry techniques, such as molecular modeling and docking studies. Furthermore, molecular dynamics (MD) calculations can help in understanding how the template interacts with monomers at different stages of polymerization, and DFT (Density Functional Theory) calculations can assist in identifying the most energetically favorable interactions, which are critical for the specificity and affinity of the MIP. This computational strategy guides the selection of monomers that create stable complexes with the target, thereby ensuring high specificity and binding affinity in the final MIP. The investigation of functional ceramic materials in molecular imprinting systems can also benefit from these computational approaches, enabling the optimization of their properties. Notably, DFT modeling can provide insights into selectivity tuning by evaluating interactions between imprinted sites and the target molecule under various conditions. This aids in selecting monomers that form stable complexes with the target, thereby ensuring high specificity and binding affinity in the final MIP [132,133,134,135]. Figure 4A illustrates the principle of computational catalyst design strategies, while Figure 4B reveals the chemical structure of a functionalized monomer, the SiO₂ ceramic matrix, and the calculated adsorption energy. This computational approach enables the optimization of MIP selectivity and affinity, facilitating the rational catalyst design for applications in sensing, catalysis, and bioactive compound separation.

It has been reported that the conditions under which MIPs are synthesized, including temperature, solvent, and initiator concentration, can significantly impact the polymer’s properties. Hence, from this perspective, theoretical approaches are crucial for optimizing these parameters to enhance imprinting efficiency and provide thermodynamic and kinetic insights into the process, thereby guiding synthesis [136]. By simulating various scenarios, researchers can identify the best conditions that lead to forming well-defined recognition sites. Additionally, DFT-based calculations can predict active site locations and interaction geometries, i.e., contributing to a deeper mechanistic understanding of the binding process. This knowledge enables the fine-tuning of MIP design to achieve desired selectivity and sensitivity. Therefore, performance prediction is crucial in MIP development, with theoretical models based on Quantitative Structure–Activity Relationship (QSAR) correlating structural features of MIPs with their binding affinities and selectivity toward guiding the design of more effective polymers [63,137,138,139].

Thus, a study developed by Sales et al. [65,140] explores the use of MIPs as synthetic receptors for drug detection, specifically focusing on MDMA, a prevalent psychoactive substance requiring effective and selective detection methods. Their research employs advanced computational approaches—molecular simulations and theoretical modeling—to design MIPs with high selectivity and affinity for MDMA and to understand the molecular interactions between the polymer’s imprinting sites and MDMA. This allowed accurate prediction of the MIP’s ability to selectively recognize and capture MDMA amidst other compounds, improving detection efficiency and reliability. The findings not only demonstrate the feasibility of MIPs as sensors for MDMA but also pave the way for broader applications in detecting other biomedical and forensic substances, making a significant advancement in analytical chemistry and smart polymeric materials for specific sensing. Nicholls et al. [141] also conducted a significant study employing computational methods —molecular modeling, MD, and molecular coupling—to predict interactions between MIP monomers and target molecules. This article highlights successful examples of applying these methods to design specific MIPs for chemical sensors, catalysis, and the separation of bioactive compounds. Integrating computational approaches with experimental methods in the synthesis and characterization of MIPs holds promise for significantly advancing the field and enabling the development of highly selective and effective polymeric materials for various technological and biomedical applications.

Integrating MIPs with ceramic materials has gained attention for the development of hybrid systems with enhanced stability and selectivity. For example, Kearley et al. [142] studied the stability, mechanical behavior, and electronic structure of ceramics to understand their potential as support matrices for MIPs. Their study, which combines inelastic neutron scattering with DFT-MD simulations, offers valuable data on the dynamics of silicon in Ti₃SiC₂, revealing insights into the material’s stability and mechanical properties for MIP–ceramic composites. Additionally, Narang et al. [143] have explored the correlation between atomic-level structures and dynamic processes such as crystallization in glass-ceramics, which can be exploited in the fabrication of MIP–ceramic composites. These studies enhance the understanding of fundamental interactions in ceramic-based MIP composites, facilitating the development of advanced materials with improved selectivity, mechanical resistance, and thermal stability for various technological applications, including sensing and catalysis [130,144].

Computational chemistry proves to be a very important and useful tool in the studies of MIPs; in fact, computational methods can reduce the costs and time associated with experimental trial-and-error approaches. Using computational tools to pre-screen monomers and predict optimal conditions, researchers can minimize the number of experimental iterations required to develop a functional MIP. This accelerates the development process and reduces resource expenditure. Furthermore, computational methods are capable of opening paths for innovative MIP applications. Their ability to provide detailed molecular insights, optimize synthesis strategies, and predict performance enhances the efficiency of MIP development and the efficacy of the final polymers, proving especially useful in designing MIP–ceramic catalysts for selective reactions. As computational techniques continue to advance, their integration into MIP design will likely lead to even more sophisticated and highly specialized polymers, expanding the potential applications of MIPs in various scientific and industrial fields [126,130]. Therefore, as discussed, theoretical methods have become indispensable in the design and development of imprinted materials and customized adsorbents, such as MIPs. Currently, many researchers are focused on the use of MIPs as catalytic support, so the next topic will be aimed at this important application of MIPs.

6. MIP/Ceramic Catalysts for Environmental Applications

MIPs are employed in a variety of environmental applications, thanks to their exceptional selectivity and binding affinity for specific target molecules. These polymers are instrumental in detecting and monitoring various environmental pollutants, including pesticides, heavy metals, pharmaceuticals, endocrine disruptors, and even microplastics across multiple matrices such as water, soil, and air [16,145,146]. For instance, in water treatment and purification, MIPs can effectively adsorb and eliminate contaminants like atrazine (a common herbicide), lead (a toxic heavy metal), and certain pharmaceuticals, thereby significantly enhancing water quality. Additionally, MIPs have shown promise in soil remediation by extracting persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), proving their effectiveness in restoring contaminated land [147,148].

A detailed review [149,150] explores the function of MIPs in the targeted detection of environmental pollutants. As previously described, MIPs are synthetic materials designed with specific cavities created by imprinting target molecules during polymerization. These cavities allow for the selective recognition and capture of specific substances, making MIPs particularly useful for detecting environmental pollutants. Furthermore, the authors show that MIPs are also employed in air quality monitoring, where sensors with MIPs detect and measure airborne pollutants such as volatile organic compounds, nitrogen oxides (NOx), and sulfur dioxide (SO₂) [151,152]. In biosensing and diagnostics, MIPs are used in biosensors to detect environmental pathogens and toxins and are applied to monitor waterborne diseases and microbial contamination in various settings. Some authors [77,153] show that MIPs offer several advantages, such as high selectivity, stability under a wide range of environmental conditions, reusability without significant loss of performance, and relatively low synthesis cost compared to traditional analytical methods.

Recent studies highlight the development of molecularly imprinted photocatalysts [153,154], which combine the robustness of traditional photocatalysis with the precision of molecular imprinting technology. These MIPs are designed to selectively degrade specific pollutants, such as diclofenac, a common pharmaceutical contaminant in wastewater. The inclusion of TiO₂ as a photocatalytic base has shown promising results, enhancing the degradation efficiency under UV light. Furthermore, MIPs can be used as photocatalysts to mitigate pollutants dangerous to the environment, the work developed by Kubiak et al. [155] shows that MIPs can function by adsorbing target molecules onto their imprinted cavities and subsequently catalyzing their degradation upon exposure to light, particularly UV or visible light. This approach not only enhances the removal of contaminants but also allows for the regeneration and reusability of MIPs, making them advantageous over traditional adsorbents and catalysts in terms of sustainability and long-term cost-effectiveness in water purification processes. With this in mind,

Table 5. Main studies published in recent years regarding the application of MIPs in environmental chemistry.

Title	Short Summary	Years
Natural and Synthetic Polymers for Biomedical and Environmental Applications [156,157].	Use of MIPs to remove heavy metals and other pollutants.	2024
Recent advancement in fluorescent materials for optical sensing of pesticides [158].	addresses the use of luminescent MIPs for pesticide detection, emphasizing their high selectivity and sensitivity.	2023
MIPs for environmental adsorption applications [159].	Study highlights the development of MIPs for the selective capture of anti-inflammatory drugs in river water samples	2022
Molecularly Imprinted Polymer-Based Sensors for the Monitoring of Antibiotic Traces and Microorganisms in Water Samples to Combat Antimicrobial Resistance [160].	This study develops MIPs for the selective detection of antibiotics in environmental water samples, demonstrating high specificity and sensitivity in detecting contaminants at very low concentrations.	2024
Development of magnetic MIPs for selective extraction of Benzoxazolinone-type alkaloids from acanthus plants [161].	The article addresses the synthesis of magnetic MIPs for the efficient extraction of pesticides from soil samples, highlighting the use of advanced characterization techniques to optimize the performance of MIPs.	2024
Application of MIPs in the Analysis of Waters and Wastewaters [160].	This research explores the use of MIPs for the adsorption and degradation of heavy metals in wastewater, showing promising results in the effective removal of metal contaminants.	2021

shows the main articles published in recent years regarding the application of MIPs in environmental chemistry.

As discussed in Table 5, these studies show significant advances in the application of MIPs for the detection and removal of pollutants in aquatic and terrestrial environments, highlighting their potential in improving environmental quality. MIPs can be used in wastewater treatment plants to degrade organic contaminants, pharmaceuticals, and other harmful substances that are difficult to remove through conventional methods. Thus, MIPs can target pesticides and herbicides that contaminate water sources, such as atrazine, glyphosate, and others [142,162]. This selectivity allows MIPs to effectively bind and remove the target contaminant from water [161].

In addition to environmental applications, MIPs have other important applications, where they can be tailored to create chiral cavities, enabling them to catalyze enantioselective reactions. This is important in the pharmaceutical industry, where the production of chiral drugs with high enantiomeric purity is crucial [163]. They can also be used to catalyze the synthesis of active pharmaceutical ingredients (APIs) with high precision, which can lead to more efficient drug production processes with reduced side reactions and higher yields [62,164]. In food safety, MIPs detect contaminants in food products, ensuring safety by identifying pesticides, mycotoxins, antibiotics, and other harmful substances.

For catalytic processes, MIPs offer a versatile platform for catalysis with applications across various fields, including environmental science, pharmaceuticals, and industrial chemistry. Their ability to provide high specificity, selectivity, and stability makes them promising alternatives to traditional catalysts and natural enzymes. Another line that we explored, in this review article, was the use of MIPs as catalytic support, which, although recent, is very important. Thus, their ability to mimic the natural recognition properties of biological receptors makes them highly valuable in various applications, including as catalytic supports. When MIPs are used as catalytic supports, they provide a unique platform that combines high selectivity with stability and reusability, offering significant advantages over traditional catalytic systems [165,166]. MIPs as catalytic supports are widely used in the pharmaceutical industry where they can work as catalytic supports and are used for the synthesis of drugs wherein high selectivity and purity are crucial [167]. They can catalyze reactions to produce enantiomerically pure compounds, which is essential for developing effective pharmaceuticals. In food chemistry, they can assist in the synthesis of flavors and fragrances, ensuring that the desired product is obtained with high specificity [139,168].

Future research should focus on improving the synthesis methods to produce MIPs more efficiently and explore new types of monomers and cross-linker agents to enhance their properties. The integration of MIPs with nanotechnology and other advanced materials science techniques also holds promise for developing more sophisticated and efficient catalytic systems [62,169,170,171,172]. As observed, MIPs as catalytic supports represent a promising intersection of materials science and catalysis, offering highly selective, stable, and reusable systems for various industrial and environmental applications. With ongoing advancements in their design and synthesis, MIPs are expected to play an increasingly important role in the development of efficient and sustainable catalytic processes.

7. Conclusions

This review article provides a general overview of heterogeneous catalysis, particularly using MIPs as catalysts or catalytic support, as well as on the use of theoretical computation for the intelligent design of such advanced materials. It is shown that MIPs represent a promising and versatile class of materials with a broad range of applications, particularly in fields such as sensing, separation, environmental, and drug delivery. The review highlights the significant progress made in the synthesis and characterization of MIPs, emphasizing their high selectivity, stability, and robustness. Advances in polymerization techniques, such as bulk, precipitation, and surface imprinting, have improved the efficiency and functionality of MIPs, allowing for more precise molecular recognition.

Despite the impressive advancements, challenges remain, including the need for more straightforward and scalable synthesis methods, improved binding kinetics, and better control over polymer morphology. Future research should focus on integrating MIPs with nanomaterials and exploring their potential in emerging areas like personalized medicine and environmental monitoring. Overall, MIP/ceramic systems have demonstrated substantial potential, and continued innovation in their design and application is expected to lead to even broader and more impactful uses. As the field progresses, the use of MIP/ceramic systems could become an essential tool in numerous scientific and industrial domains, paving the way for significant technological advancements.