## 5 Conclusions and Outlook  
Materials science offers a large range of different crystalline structures that may present a simple chemical composition, such as the molecular sieves discussed called zeolites. These structures are obtained by various methods: high energy consumption processes due to heating and long reaction with either stirring or static conditions, or the so-called facile route of synthesis, using microwave and ultrasound to minimize reaction time, leading to energy saving. The use of mineralizer agent of an alkaline nature is necessary and influences the size of the formed particles. Other parameters such as aging, temperature, crystallization time, the use of an amorphous seed, and the use of a synthetic precursor are also of critical importance in zeolite properties. The incorporation of heteroatoms in structures is important to improve catalytic activity by combining the (photo)catalytic property of some metals and the shape selectivity of zeolite pores. Thermal and mechanical resistance in various reaction conditions is commonly reached for these materials. As an example, the addition of zeolites to waste precursors in petroleum industry processes are necessary in order to shift to an eco-friendlier position. The aggregation of other materials that are used as synthesis precursors to compose the zeolite framework is advantageous in the recovery of waste. Therefore, zeolite synthesis accomplishes the features of a green material, using wastes as precursors, minimizing energy costs through facile synthesis routes, and allowing the incorporation of biomolecules in microorganisms as well as catalyzing the conversion of biomass in useful molecules. These products could act as platform molecules in different applications in the pharmaceutical, food, and cosmetics sectors. Zeolites are often called \"zeozymes\" because of their high specificity, even in reactions involving huge molecules. This property and other factors make them potential material for specific enzyme immobilization. Incorporating the increase in features found in these macromolecules that exists to a huge extent in the variety of zeolite structure would lead \begin{table}
\begin{tabular}{c c c c} \hline
**Approach** & **Zeolite Type** & **Main Considerations** & **Reference** \\ \hline \multirow{8}{*}{**Gas adsorption**} & \multirow{2}{*}{5A (LTA)} & Separation of propane and propylene, saving energy consumption involved in distillation process. & [360] \\ \cline{2-4}  & & The structure synthesized by ultrasound assisting hydrothermal method showed good separation of CO2/CH4 and CH4/N2 mixture. & [361] \\ \cline{2-4}  & & Good selective adsorption capacities due internal electrostatic fields in structure. Adsorption of CO2 with dependence of temperature. & [362] \\ \cline{2-4}  & & NaX presented high separation for mixture CO2/CO and CaA (LTA) and CaA presented high separation stability for the same mixture. & [363] \\ \hline \multirow{8}{*}{**Water treatment**} & \multirow{2}{*}{LTA and FAU} & The mechanism of absorption of nickel metal ions was strongly related to the architecture of the pores, while the exchange of copper and lead was related to the cation exchange properties of the zeolite structure. & [364] \\ \cline{2-4}  & & The selectivity sequence of cation adsorption can be given as Pb2+ \(>\) Cd2+ \(>\) Cu2+ \(>\) Zn2+ \(>\) Ni2+ & [365] \\ \cline{2-4}  & & The adsorption of cyanide anion was tested. The cyanide loading was a maximum of 24 mg/g of zeolite and the ideal solution pH was 7 or less & [366] \\ \cline{2-4}  & & Structures useful in adsorption of dyes. The mechanism of the adsorption processes was controlled by three successive stages, i.e., internal diffusion, external diffusion and pore diffusion processes & [367] \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._to potential applications in biofuel production or biocatalysis. The large variety of zeolitic structures might be explored together with the large variety of enzymes from different sources to explore new potentialities.