New inorganic and hybrid framework materials

• Main Author: Nicholls, Jennifer
• Other Authors: Fogg, Andrew
• Published: University of Liverpool 2012
• Subjects: 540
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.559432

This thesis describes the formation of new inorganic and hybrid framework materials, from cationic layered structures through to three-dimensional frameworks, with potential applications in catalysis, gas storage and anion exchange. A study of the formation of a number of these materials is also discussed within this thesis. Chapter 1 presents a review of literature covering the area of hybrid and also cationic materials. This includes a discussion of hybrid materials such as coordination polymers and metal organic frameworks (MOFs), and also cationic materials such as layered double hydroxides (LDHs) and three recently reported cationic inorganic frameworks. Chapter 2 describes the hydrothermal synthesis of six new pillared layered lanthanide molybdate and tungstate phases. Five of these phases have a general composition of [Ln(H2O)MO4]2[A] (Ln= La- Nd, M = MoO4 or WO4, A = 1,5-NDS or 2,6-NDS) with the sixth phase, being pillared by fumarate, having the composition [Ce(H2O)MoO4]2[Fumarate]. Each phase consists of two-dimensional cationic inorganic layers comprising of a bilayer of polyhedra and are pillared by charge-balancing organic dianions. The catalytic and anion exchange capabilities of the NDS materials were tested. It was discovered that these materials are able to undergo successful anion exchange of the NDS anions, with dicarboxylates such as fumarate, terephthalate and 2,6-NDC. The tungstate containing phases were also tested for their catalytic properties and proved to be successful catalysts for the oxidative bromination of phenol red to bromophenol blue. Chapter 3 describes the hydrothermal synthesis of three new lanthanide phosphonoacetate coordination polymers, two having a general formula of [Ln(H2O)2][C2H2O5P] (where Ln = Er, Ho and Tb or Yb and Lu), which have infinite three-dimensional structures containing discrete LnO7 polyhedra connected together via O-P-O bridges, and the remaining phase having a composition of [YbC2H2O5P] consisting of one-dimensional chains of LnO7 polyhedra which are held together via pillaring phosphonoacetate anions to form a three-dimensional network. Porosity measurements confirmed each phase to be non-porous. Also hydrothermally synthesised are two organosulfonate coordination polymers with compositions of [Ln(H2O)5]2[2,6-AQDS]3•2H2O (Ln = La - Nd) and [Ln(H2O)5][C8H17SO3]3.2H2O (Ln = La and Nd). The former phase consists of layers of monomeric Nd polyhedra which are linked by 2,6-AQDS anions forming a three-dimensional network and the latter phase consists of two-dimensional layers of monomeric lanthanum cations which are bridged together by octanesulfonate anions to form a two-dimensional layered structure. Chapter 4 describes the study of the formation of pillared layered lanthanide molybdate and tungstate phases and also the dehydration of [Yb(H2O)2][C2H2O5P] to [YbC2H2O5P] using the in-situ energy dispersive X-ray diffraction technique. In-situ measurements of the formation of neodymium/molybdate/NDS phases allowed the observation and successful isolation of an intermediate phase which was detected during the formation of the required phase. Kinetic analysis, including calculation of the activation energy, was achieved for the formation of [La(H2O)WO4]2[1,5-NDS]. Also observed by in-situ measurements was the dehydration of [Yb(H2O)2][C2H2O5P] forming [YbC2H2O5P], which occurs via a dissolution/re-precipitation mechanism. Chapter 5 describes the boric acid flux preparation of lanthanide borate compounds with compositions [Ln(NO3)(H2O)2][B6O10(OH2)] (1) (Ln = La and Ce), [Ln(NO3)(H2O)2][B5O9(OH2)] (2) (Ln = Pr and Ce), and [Ln(B6O13H3)][BO3H2] (3) (Ln = Sm, Eu and Gd). 1 and 2 are found to have infinite three-dimensional structures consisting of either hexaborate clusters as found in 1 or pentaborate clusters as found in 2, with one dimensional channels being present in both structures. 3 differs to 1 and 2 as a two-dimensional layered structure is formed consisting of positively charged layers of gadolinium cations coordinated to unique hexaborate clusters, which are charge balanced by non-coordinating borate anions residing in the interlayer gallery. The anion exchange capabilities have been tested for 3 although this proved largely unsuccessful. Chapter 6 gives details of the syntheses of all the phases prepared during the course of this study and the analytical techniques used to characterise them.