Herein k ads j denotes the rate coefficient of reaction j if it is an adsorption, µ is the number of reactant molecules and sites partaking in the adsorption (µ = 2 in most cases e.g. simple adsorption), M ads i is the molar mass of the gas-phase molecule adsorbed in that step and Γ 0 denotes the overall active site density of the catalytic material. It can be shown easily that above parameterization is consistent to the overall formalism presented in eqs. (1) to (3) and can be rewritten accordingly. For more information see appendix SI A. One can easily see that the number of unknowns in this system quickly explodes even for simple systems leading to the development of simpler (almost surrogate) kinetic expressions. The most commonly used kinetic expressions are of the Langmuir-Hinshelwood-Hougen-Watson (LHHW)-type. They derive from assuming a simple surface reaction network of adsorption and reaction steps under the assumption of equilibrated and rate-determining steps (RDSs). Therefore, they are analytically closed, obey the respective adsorption and reaction equilibria and reproduce kinetic behavior near steady-state . Unfortunately, it has been shown repeatedly that the approximation of surface processes by steady-state kinetics does not provide sufficient detail to derive insights into the system behavior as it undergoes transient changes . To encapsulate these dynamic processes MKMs that contain all the aforementioned complexity are sought.