Multifunctional Metal-Organic Frameworks (MOFs) For Applications in Sustainability

Climate change, affordable and clean energy, and responsible consumption and production are some of the important goals to be achieved for sustainable development. The current technologies used to address these challenges are energy and resource intensive. Furthermore, there are various limitations related to cost, storage, scalability and safety.Adsorbent materials are seen as a promising alternative remediation system due to their low energy consumption and minimal chemical waste production. However, most of the traditional adsorbents, such as activated carbon and zeolites lack the structural tunability to have long-term effectiveness and their use is limited. As discussed in Chapter 1, metal organic-frameworks (MOFs) are a class of advanced porous materials which have been successful in a variety of applications due to their high degree of structural tunability, diverse range of structures and excellent designability. This work focuses on their use in cabon capture and conversion, methane storage and sustainable catalysis. Chapter 2 explores the mitigation of CO2 and its subsequent utilization to synthesize value added chemicals. The first partially interpenetrated metal-organic framework with nbo topology is obtained that exhibited selective adsorption of CO2 over CH4. Due to presence of high density of catalytically active sites, it additionally shows excellent catalytic efficacy for the cycloaddition reaction of CO2 with epoxides to produce industrially important cyclic carbonates in more than 90% yields using solvent-free conditions. Chapter 3 details the work to employ stable soc-MOFs based on iron and aluminum for on-board methane storage under DOE operational conditions. Emerging as an outperformed class of MOFs, square-octahedron (soc) topology MOFs (soc-MOFs) feature superior properties of high porosity, large gas storage capacity, and excellent thermal/chemical stability. Iron and aluminum based soc-MOFs possessing a very high Brunauer, Emmett and Teller (BET) surface areas and large pore volumes are obtained. Furthermore, the MOFs exhibit high thermal and aqueous stability. The iron MOF demonstrates by far the highest gravimetric uptake of 369 cm3 (STP)/g under the DOE operational storage conditions (35 bar and 298 K) and a high volumetric deliverable capacity of 192 cc/cc at 298 K and 65 bar. These results in totality promote ANG technology and make these frameworks promising candidates for on-board methane storage. Chapter 4 concentrates on use of discrete bifunctional nanoball metal organic cuboctahedra for one-pot tandem catalysis. The co-existence of Lewis base pyridine group and Lewis acid copper site render the MOP efficient catalytic activity for the one-pot deacetalization Knoevenagel reaction of benzaldehyde diacetal and malononitrile. The target product is obtained in excellent yield using DMSO as the solvent. The catalyst is also easily separated using centrifugation and can be recovered in good yield. The good catalytic activity and recyclability without significant loss in catalytic activity during the cycling experiments are additional advantages. This also opens a new platform into utilizing these nanoball architectures for catalysis. Chapter 5 utilizes an indium-based MOF as a highly efficient catalyst for one-pot, solvent free multicomponent catalysis. The MOF has the robust soc-topology and dispalys the highest BET surface area among reported indium MOFs. It acts as a heterogeneous Lewis acid-base catalyst for highly efficient conversion in one-pot multicomponent Strecker reaction of ketones in solvent-free conditions. Moreover, the heterogeneous catalyst is easy to separate and shows negligible loss of activity for over four cycles. The In-pbpta thus provides a sustainable and efficient catalytic platform for the Strecker synthesis of [U+F061]-aminonitriles which can be further hydrolyzed to give the unnatural [U+F061]-amino acids. This work overall demonstrates the successfull use of multifunctional MOFs for applications in sustainability.Through optimization of the design of the material based on well defined topologies, and functionalization for the desired application, a high activity is observed leading to energy and process efficiency. Through further optimization of the design, these approaches can not only ensure a progress towards sustainable development and processes, but also advance MOFs for their commercial large-scale usage