Table 1.

Distinguishing features of sol-gel and hydrothermal process.

Distinction	Sol-gel process	Hydrothermal process	References
Process	This process involves two main steps of synthesis, including the formation of particles in solution followed by gel formation due to the 3D polymeric network.	In this process, an inorganic substance is added to the templating agent (acid or alkali), and the fabricated hydrogel is afterward subjected to autoclaving.	(Varshney et al., 2021)
Reaction conditions	In this process, the requirement of a sealed container is not required.	The reaction takes place in a sealed container, having maintained temperature and pressure.	(Mohamed Isa et al., 2021; Yu et al., 2012)
Requirement of Autoclave	The method doesn’t require autoclaving or any other parameter of high temperature.	The method requires a Teflon-lined autoclave to maintain process parameters.	(Yu et al., 2012)
Formation of mesoporous particles	Desired morphology is obtained through simultaneous hydrolysis and condensation of metal oxide.	The powdered solid SiO2 got dispersed during heat treatment, and the formation of mesophase assembly occurs after the removal of heat.	(Galabova, 2021).
Morphology of MSNs	Formulation parameters, such as temperature, pH, and reagent concentrations, affect the morphology and size of the particles.	Particle morphology and size have a significant influence on cooling rate after thermal treatment.	(Narayan et al., 2018)
Advantages	The main advantages include increased purity and ease of synthesis at moderate reaction conditions	The advantage of this method is to obtain of MSNs having greater hydrothermal stability.	(Bharti et al., 2015; Shahbazi et al., 2012) (Lin et al., 2011).
Disadvantages	The method produces particles in micron size and requires further modifications	The process is complex and requires increased time.	(Miller et al., 2014).