Open framework materials (OFM) constitute a large and growing class of nanoporous crystalline structures that is attracting considerable attention for electronic device applications. This review summarizes the most recent reports concerning electronic devices enabled by either of the two primary categories of OFM, metal–organic frameworks (MOFs) and covalent–organic frameworks (COFs). Devices in which the OFM plays an active role (as opposed to acting only as a selective sorbent or filter) are the principal focus, with examples cited that include field-effect transistors, capacitors, memristors, and a wide variety of sensing architectures. As a brief tutorial, we also provide a concise summary of various methods of depositing or growing OFM on surfaces, as these are of crucial importance to the deployment of electronic OFM. Finally, we offer our perspective concerning future research directions, particularly regarding what in our view are the biggest challenges remaining to be addressed. On the basis of the literature discussed here, we conclude that OFM constitute a unique class of electronic materials with characteristics and advantages that are distinct from either conventional inorganic semiconductors or organic conductors. This suggests a bright future for these materials in applications such as edge computing, resistive switching, and mechanically flexible sensing and electronics.

Open-framework inorganic and inorganic-organic hybrid materials constitute an important area of study in materials chemistry, because of their potential applications in areas such as sorption and catalysis. Besides aluminosilicate zeolites, the metal phosphates and carboxylates constitute large families of open-framework structures. The possibility of building open architectures with the sulfate and selenate anions as the basic building units has been explored in this thesis. Investigations of a variety of open-framework metal sulfates and selenates, as well as a family of jarosites of different transition metals are presented. More importantly, studies directed towards the synthesis and understanding of the magnetic properties of various Kagome compounds formed by the transition metal ions is discussed at length. After providing an introduction to inorganic open-framework compounds (Part 1), the thesis presents the results of the investigations of various transition and rare earth metal sulfates with diverse structures and dimensionalities in Part 2. Some of these compounds show interesting properties. For example, a two-dimensional Ni(II) sulfate exhibits ferrimagnetism whereas a three-dimensional Ni(II) sulfate with 10-membered channels is paramagnetic. A family of three-dimensional co-ordination polymers of Co(II) sulfate wherein the Co(II) sulfate layers are linked by diaminoalkanes of varying chain length has been synthesized and characterized. Organically-templated neodymium and thorium sulfates with layered and three-dimensional structure have also been prepared. The jarosite family of compounds with the Kagome structure is considered as an ideal model for studying frustrated magnetism. This type of materials, however, is difficult to prepare in a pure and highly crystalline form. We have synthesized analogues of the jarosite containing magnetic ions other than Fe3+ by solvothermal techniques and discussed them in Part 3. In particular, we have prepared and explored the magnetic properties of Mn2+(S = 5/2), Fe2+ (S = 2), Co2+(S = 3/2) and Ni2+ (S = 1) jarosites. Based on the results presented, it becomes clear that the magnetic properties vary with the spin of the transition metal ion. It appears that those Kagome compounds with transition metalions with non-integer spins show antiferromagnetic interactions and magnetic frustration while those with integer spins exhibit ferro/ferrimagnetic properties. A theoretical study has also supports this observation. We have been able to isolate for the first time 1,4-diazacubane as the part of the structure of the nickel Kagome compound. The possibility of building open architectures with the selenate anion as the basic building unit has been explored in Part 4. The results have been rewarding and an organically-templated three-dimensional lanthanum selenate with 12-membered channels has thus been obtained for the first time.

Open-framework inorganic materials constitute an important area of study in materials chemistry, because of their potential applications in areas such as sorption and catalysis. After the discovery of nanoporous aluminium phosphates by Flanigen et al in 1982, there has been a tremendous growth in the area of porous solids. Most of them are based upon oxygen containing materials especially phosphates, and they exhibit fascinating architectures with unusual bonding and coordination environment. Besides metal phosphates and phosphites, inorganic-organic hybrids constitute an important family of open-framework structures. In this thesis, results of investigations of a variety of open-framework metal phosphates, metal phosphites, as well as a new family of phosphite-oxalates are presented. More importantly, studies directed towards the synthesis and understanding of the magnetic properties of various transition metal phosphates, phosphites, phosphite-oxalates and the upconversion behavior of uranium phosphites are discussed at length. In Chapter 1 of the thesis an overview of inorganic open-framework materials is presented. In Chapter 2 and 3, the synthesis, structure of open-framework zinc (Part A of both Chapters) and synthesis, structure and magnetic properties of open-framework iron (Part B of both Chapters) are presented. Some of these compounds show unusual structure and interesting properties. For example, two-dimensional iron phosphate exhibits ferrimagnetism whereas three-dimensional iron phosphate with SBU-6 and SBU-2 is antiferromagnetic. The three-dimensional iron phosphite exhibits small polarization at low field. In Chapter 4, we present a new family of organically templated hybrid materials synthesized by partially substituting the phosphite by the oxalate ion in manganese, iron and cobalt phosphites. These exhibit a wide range of structures in which the oxalates play an unusual dual role. Some of these compounds show interesting magnetic properties. For example, manganese phosphite-oxalate shows magnetic polarizations on application of high field at low temperatures and iron phosphite-oxalate exhibit ferromagnetism at very low temperature. While a large number of organically templated transition and main-group element phosphites have been synthesized, research on lanthanide and actinide phosphites has been rare. Most of the reported open-framework phosphate and phosphite compounds of uranium possess uranium in +6 oxidation state. The possibility of building open architectures of uranium phosphites has been explored in Chapter 5. The results have been rewarding and both layered and three-dimensional structures have been prepared. Two of them contain uranium in +4 state and exhibit upconversion behavior.

Open-framework inorganic materials constitute an important area of study in materials chemistry, because of their potential applications in areas such as sorption and catalysis. After the discovery of nanoporous aluminium phosphates (AlPOs) by Flanigen et al in 1982, there has been a tremendous growth in the area of porous solids that are based on phosphates. Apart from phosphates, phosphites, arsenates, sulfates, sulfites, selenates, selenites etc. have also been investigated. In addition to the different anions, the framework compounds now encompass almost all the elements of the periodic table. The compounds exhibit wide variety and structural diversity. New building units, such as thiosulfate and borate have also been explored as a network builder in the formation of framework structures. In this thesis, the results of the investigations on open-framework metal thiosulfates, metal borates and metal sulfates are presented. The studies are aimed not only at the synthesis of the new compounds based on the new anions, but also their possible applications. In Chapter 1 of the thesis an overview of inorganic open-framework materials with different anions is presented. In Chapter 2 (Part A), the synthesis, structure and transformation of inorganic-organic hybrid open-framework cadmium thiosulfate are presented. The lack of stability of the thiosulfate ion in solution prompted the exploration of new approaches such as low temperature solvothermal methods, use of rigid linkers etc. The transformations of lower to higher dimensional structures have been accomplished. The possible mechanisms for such transformations were investigated. In Part B, the physical and chemical properties of the hybrid cadmium thiosulfate frameworks are presented. The studies indicate that the anionic dyes selectively adsorb on the compounds in the water medium and also desorb reasonably in alcoholic medium. The cadmium thiosulfate compounds appear to be reasonable photocalysts for the photodecomposition of the cationic dyes under UV irradiation as well as under sunlight with good recyclability. The compounds also exhibit heterogeneous catalytic behavior (Lewis acidity) for the cyanosilylation of the imines. In Chapter 3, a new family of organically templated open-framework borate materials is presented. The zinc and aluminoborate structures, prepared in the present study, are rationalized using the HSAB theory. The [B4O9H2] units polymerize differently to form different zinc borate structures. The amine molecules act as a ligand by binding with the metal. The nature of the amine appears to control the dimensionality of the final zinc borate structures. The zinc borate compounds exhibit absorption of UV-light (λ = 365 nm) suggesting that the zinc borate compounds could be exploited for UV-blocking applications. Organically templated aluminoborates have connectivities between the Al3+ ions and the [B5O10] cyclic pentaborate units. The aluminoborate structures exhibit graphite layer and three-dimensional diamond structure. Detailed studies and comparison of the various amine templated open-framework aluminoborate structures reveals subtle relationships between the organic amines (shape and length of the amines) and the final framework structures. In Chapter 3, the synthesis, structure and catalytic studies of a variety of cadmium sulfate phases have been carried out. Polyazaheterocyclic ligands were employed to study their possible role in the formation of such structures. All the compounds have structures built up by the connectivity involving the cadmium octahedra and the sulfate tetrahedra in which the heterocyclic organic molecules act as the ligand. The connectivity between the Cd2+ and (SO4)2− ions form one-, two-and three-dimensionally extended cadmium sulfate phases, though the starting source is cadmium sulfate (CdSO4.8/3H2O) in all the cases. The connectivity between Cd2+ ion and the heterocyclic ligand also gives rise to one-and two-dimensional structures. The interconnectivity between the two units gives rise to the final observed structure. As part of the study, a variety of properties i.e. adsorption-desorption, photocatalytic degradation and cyanosilylation reaction, exhibited by the cadmium sulfate compounds have been investigated and the properties are comparable to the cadmium thiosulfate phases. AlPOs are well known for their many important properties. The wide varieties in their structures and heterogeneous catalytic properties have been extensively investigated. The photocatalytic behaviors, on the contrary, have not been investigated in detail. The photocatalytic properties of the metal-doped AlPOs, for the photodegrdation of organic dyes have been investigated in the Chapter 5. The metal ions (Mg2+, Zn2+ and Co2+) have been substituted in place of Al3+ and Ti4+ in place of both the Al3+ and P5+ in a variety in AlPO structures and the synthesized phases are characterized by a variety of techniques. Photodecomposition studies of organic dye molecules under UV-light were carried out in aqueous medium. The studies suggest that the photocatalytic activity is reasonable and appears to depend on the dopant concentration. Ti-substituted phase exhibits the maximum catalytic activity.

Open–framework inorganic materials are an important class of compounds because of their many applications in the areas of ion–exchange, separation and catalysis. Ever since the discovery of microporous aluminophosphates by Flanigen and co–workers in the early 80’s, the field of open–framework compounds has witnessed explosive growth. It is now established that the open–framework compounds comprise of almost all the elements of the periodic table. In addition, it has been shown that the inorganic anions in the open–framework compounds can be partially substituted by rigid organic linkers such as the oxalate. The resulting inorganic–organic hybrid structures are interesting due to the variable nature of the binding properties of the organic and inorganic moieties. The present thesis consists of systematic studies on the formation of amine–templated inorganic open–framework structures and inorganic–organic hybrid compounds based on the main group, transition metal and actinide elements. In Chapter 1 of the thesis an overview of inorganic open-framework materials is presented, with an emphasis on the elements that have been employed in the present study. Chapter 2 has two parts (Parts A and B) describing the synthesis and structure of open-framework tin(II) containing compounds. In Part A, the syntheses and structures of amine–templated tin(II) phosphates are presented, and in Part B, the syntheses and structures of a family of tin(II) oxalate compounds are discussed. Weak intermolecular forces such as hydrogen-bond interactions, π•••π interactions, and lone-pair–π interactions have been observed in these compounds, and appear to lend structural stability. As part of this study, efforts have been made to evaluate the energies associated with the π•••π interactions and the lone-pair–π interactions using suitable theoretical models. In Chapter 3, a new family of organically templated hybrid materials based on indium, synthesized by partially substituting the inorganic anion (phosphite/phosphate/suphate) by the oxalate group, is presented. These compounds exhibit a wide range of structures in which the oxalates play a variety of roles. The observation of the first zero-dimensional molecular hybrid structure and the isolation of concomitant polymorphic compounds is noteworthy. The molecular hybrid structure is reactive and undergoes transformation reactions under both acidic and basic conditions. In Chapter 4, the synthesis and structural studies of five new open–framework phosphate and phosphite compounds of gallium are presented. All the compounds have three-dimensional structures, and the formation of a gallium phosphate based on only one type of building unit (spiro–5) is noteworthy. While a large number of organically templated transition metal phosphates have been synthesized, studies on transition metal phosphites are not many. In Chapter 5, the synthesis, structure and magnetic properties of a family of transition metal (cobalt, vanadium, manganese) phosphite structures templated by the organic amines are presented. A previously known vanadyl phosphite has also been isolated and investigated by temperature dependent ESR and magnetic susceptibility studies. All the transition metal compounds exhibit antiferromagnetic behavior. In Chapter 6, the synthesis, structure, and transformation reactions in amine-templated actinide phosphonoacetates are presented. The compounds, which are based on uranium and thorium, are built up from the connectivity between the metal polyhedra and the phosphonoacetate/oxalate units, forming two– and three–dimensional structures. It has been shown that the two–dimensional uranyl phosphonoacetate–oxalate compound can be prepared by two different synthetic approaches: (i) solvent–free solid state reaction at 150˚C and (ii) room temperature mechanochemical (grinding) route. The formation of oxalate hybrids using the phosphonocarboxylate ligand is a new approach in the synthesis of multi-component hybrid compounds.