The physicochemical properties of mesoporous materials like MCM-41 are directly affected by their structural characteristics. These materials are formed from tetrahedral units like SiO4 or can contain other metals from Groups III or IV. Computer modeling is an important tool for understanding the real structure of these materials. The study proposes a theoretical model using TO4 units to model Lewis and Brønsted acid sites on the surface in order to study the surface acidity of materials like MCM-41. Initial results show changes in the geometry of the unit from tetrahedral to triangular planar when T is Ga compared to when T is Al.

1. Analysis of the change in the geometry of the active site in
substituted mesoporous materials MCM-41
Gabriel Herrera-Pérez
Departamento de Ingeniería en Materiales, Instituto Tecnológico Superior de Irapuato
(ITESI) Carretera Irapuato-Silao Km. 12.5, El Copal, Irapuato, Guanajuato.
C.P.36821. México. e-mail: gaherrera@itesi.edu.mx
The physicochemical properties of the mesoporousos materials among them the MCM-
41 (Material Composition Material - 41), are affected directly by the structural
characteristics. These materials can be in favor only formed of tetrahedral units (SiO4)-
4 or also to contain other metals of Group III or IV mainly. The versatility of materials
MCM is that they have been possible to announcer functional groups in the surface.
Therefore, the application of computer chemistry in order to generate models that allow
supporting in the elucidation of the real structure of the material has turned into a
substantially important tool. Inserting functional groups or replacing silicon atoms of
another element is in order to affect the chemical reactivity, which can be evaluated by
means of the parameters of the acidity, hardness-softness between some others.
The zeolites and zeotypes present a high crystalline concerning the tetrahedral units
that imagine generally like TO4, where T represents an atom of If or the substituted
metal like B, Al, Ga, In among others. But for the case of the mesoporous materials,
the certainty does not exist on its microstructure, are material amorphous that present
their crystalline long reach, referred is to the distribution of the mesoporous. The
general mission of this proposal is to propose a model with units TO4 to construct to
the sites Lewis and/or Brönsted for the study of the superficial acidity of the material.
The cell-calculation its called T8 sets out to the marries of to secondary crystalline unit
4-4, the development of this work considers to replace an atom T by to another atoms
of B, Al and Ga, this cell is relatively small and thermodynamically favorable, this type
of cubical box is very common in the zeolites. In order to it determines the potential
Energy, optimization of geometry, electronic charge distribution and calculation of
orbital Energy of to to border plows realised ab initio with to level of calculation ace
much with the Hartree-Fock methodology (HF) like Theory of the Functional ones of
Densidad (DFT), would sees realised the calculations with base-set of 6-31G (2d, p). In
the figure one is T8 group whit chemical composition SiO2 and hydroxilado as
deshydroxilado for the calculation of the energy is considered power and to obtain
optimized geometry.
In initial results have been changes in the geometry unit, happening of a tetrahedral
geometry of the triangular plane T. These changes of geometry are favors in the case
of T = Ga in comparison of the case T = Al.

2. Estudio cuántico de los sitios activos de materiales mesoporosos
Dr. Gabriel Herrera Pérez
Instituto Tecnológico Superior de Irapuato ITESI
Departamento de Ingeniería en Materiales
Las propiedades fisicoquímicas de los materiales mesoporosos entre ellos el MCM-41 (Mobil
Composition of Matter), están directamente relacionadas por las características estructurales.
-4
Estos materiales están formados por unidades tetraédricas (SiO4) o también sustituidos estos
grupos por un átomo tipo metal del grupo III o IV principalmente. La versatilidad de los
materiales MCM es que se han podido a los grupos funcionales de cambiar las propiedades de
la superficie. Por lo tanto, la aplicación de la Química Computacional permite generar modelos
que permitan apoyar en la elucidación de la estructura real del material y actualmente se ha
convertido en una herramienta sustancialmente importante. La inserción de grupos funcionales
o sustitución de átomos de silicio por otro elemento es con la finalidad de afectar la reactividad
química, que pueden ser evaluados por medio de los parámetros de la acidez.
Por ejemplo las zeolitas y zeotipos presentan una cristalinidad alta, representado el átomo
tetraédrico T y el óxido como TO4, donde T puede representar también el metal sustituido
como B, Al, Ga, In, entre otros. Sin embargo, para el caso de los materiales mesoporosos, la
certeza no existe en su microestructura, ya que son materiales amorfos que presente su
cristalinidad a largo alcance. El objetivo general de esta propuesta es proponer un modelo
teórico para describir a los sitios ácidos tanto tipo Lewis como Brönsted para el estudio de la
acidez superficial del material MCM-41.