## 3 Overview of Molecularly Imprinted Polymers as Catalysts and Support for Catalysts
### MIPs as Efficient Catalytic Supports
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 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 mg\({}^{2}\)/g to 143 mg\({}^{2}\)/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 Fe\({}_{2}\)O\({}_{3}\) and Fe\({}_{2}\)O\({}_{3}\)@SiO\({}_{2}\) as catalysts in some cases suggests potential modifications in surface properties that could \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Functional** & **Molecule** & **Poorgenic Solvent** & **Catalyst** &
\begin{tabular}{c} **BET** \\ **(m\({}^{2}\)/g)** \\ \end{tabular} & **Q\({}_{\text{max}}\) (mg/g)** & **Ref.** \\ \hline \multirow{6}{*}{Methacrylate Acid (MMA)} & 17-\(\beta\)-estradiol & Acetonitrile & — & 128 & 42 & [107] \\ \cline{2-6}  & Nicotine & Methylene chloride & — & 97 & 55 & [108] \\ \cline{2-6}  & 3-Methylindole & Toluene & Fe\({}_{3}\)O\({}_{4}\) & 112 & 64 & [109] \\ \cline{2-6}  & Oxytetracycline & Water & Fe\({}_{3}\)O\({}_{4}\) & 85 & 37 & [110] \\ \cline{2-6}  & Glutathione & Acetonitrile/toluene & — & 143 & 58 & [111] \\ \cline{2-6}  & Dienoestrol & Acetonitrile & Fe\({}_{3}\)O\({}_{4}\)@SiO\({}_{2}\) & 134 & 49 & [112] \\ \hline \multirow{6}{*}{Acrylic acid} & Red Remazol & Dimetilformamido & Fe\({}_{3}\)O\({}_{4}\) & 120 & 63 & [113] \\ \cline{2-6}  & Methanoic acid & Acetonitrile/toluene & Fe\({}_{3}\)O\({}_{4}\)@SiO\({}_{2}\) & 110 & 51 & [114] \\ \cline{2-6}  & Aristolochic acid & Dimethylformamide & — & 115 & 56 & [115] \\ \hline \multirow{6}{*}{4-VP} & Ibuprofen & Acetonitrile & — & 120 & 50 & [116] \\ \cline{2-6}  & Caffe acid & Dimethylformide & — & 130 & 60 & [117] \\ \cline{1-1} \cline{2-6}  & methocarbamol & Tetrahydrofuran & — & 110 & 47 & [118] \\ \cline{1-1} \cline{2-6}  & 4-nitropenol & Acetonitrile & Fe\({}_{3}\)O\({}_{4}\) & 140 & 55 & [119] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Performance of MIPs with Different Functional Monomers and Porogenic Solvents. influence adsorption performance.