Beyond Nitrogen OSDAs

Host–Guest and Guest–Guest Interactions of P- and N-Containing Structure Directing Agents Entrapped inside MFI-Type Zeolite by Multinuclear NMR Spectroscopy

“…[8][9] The synthesis of zeolites is usually assisted by using organic molecules, the so called organic structure directing agents (OSDA), generally based on tetraalkylammonium cations, which fill the void volume of the structure and direct the crystallization towards specific topologies. 6,10 The interest in developing new zeolites, mainly aimed at obtaining materials with novel structures, wider chemical compositions and/or modified textural properties has motivated the research on synthesis strategies comprising the use of new OSDA molecules, 9,[11][12] the incorporation of heteroatoms into the framework favoring the crystallization of specific structures (Ge, Zn,…), [13][14] or the dual-template procedure using OSDAs of different nature. [15][16] Moreover, other synthesis variables such as the presence of hydroxyl groups in basic media or Fin almost neutral gels play a key role on the characteristics of the final material.…”

“…Therefore, deeper knowledge on the driving forces involved in the zeolite crystallization as well as on the non-bonding interaction of the OSDA molecules among them and with the inorganic crystalline network is needed for advancing towards the rational design of zeolites synthesis. In the last years our group has been working on a new family of OSDAs containing phosphorus (P-OSDA) which have shown a great potential for the synthesis of novel zeolites structures, widening the number of available molecules that can be used as directing agents, 12,[24][25] but also providing a new characterization tool for understanding the nature of the OSDA entrapped inside of the zeolite voids by means of 31 P MAS-NMR. From the point of view of the resulting materials, it is well known that extraframework phosphorus, which stabilizes framework aluminum against thermal treatment, cannot be introduced in small pore zeolites by post synthesis treatment because of sterical constraints.…”

“…One of the key features of zeolites is the dimensionality and sizes of their channels and cavities that provide them real molecular sieving properties, favoring the diffusion of some compounds or the formation of specific transition states, controlling gas separation and product selectivity in catalytic processes. , The synthesis of zeolites is usually assisted by using organic molecules, the so-called organic structure directing agents (OSDA), generally based on tetraalkylammonium cations, which fill the void volume of the structure and direct the crystallization toward specific topologies. , The interest in developing new zeolites, mainly aimed at obtaining materials with novel structures, wider chemical compositions, and/or modified textural properties has motivated the research on synthesis strategies comprising the use of new OSDA molecules, ,, the incorporation of heteroatoms into the framework favoring the crystallization of specific structures (Ge, Zn, ...), , or the dual-template procedure using OSDAs of different nature. , Moreover, other synthesis variables such as the presence of hydroxyl groups in basic media or F – in almost neutral gels play a key role on the characteristics of the final material. Fluoride is usually incorporated within the smallest zeolite cages ,, compensating the positive charge of the OSDAs cations, and in some structures, it bonds silicon atoms giving five-coordinated framework F–SiO 4 sites. , Synthesis in fluoride media gives crystals free of connectivity defects whereas silanol groups are abundant in the materials synthesized in basic media.…”

“…In the last years our group has been working on a new family of OSDAs containing phosphorus (P-OSDA) which have shown a great potential for the synthesis of novel zeolites structures, widening the number of available molecules that can be used as directing agents. ,, Moreover, P-OSDAs provide a new characterization tool for understanding the nature of the OSDA entrapped inside of the zeolite voids by means of 31 P MAS NMR. From the point of view of the resulting materials, it is well-known that extra-framework phosphorus, which stabilizes framework aluminum against thermal treatment, cannot be introduced in small pore zeolites by postsynthesis treatment because of sterical constraints.…”

Síntesis y caracterización avanzada de materiales zeolíticos mediante el empleo de nuevos agentes orgánicos directores de estructura

“…La naturaleza química de los compuestos orgánicos empleados como ADE en la síntesis de zeotipos es muy variada. Las especies más comunes son derivados de tetraalquilamonios, aunque entre los compuestos empleados podemos encontrar: tetraalquilfosfonios, [166] tetralaquilarsonios, [167] tetraalquilsulfonios, [168,169] complejos de cationes alcalinos con éteres corona [170][171][172] , compuestos organometálicos, [173][174][175] entre otros.…”