Thanks to their modular design, metal-organic frameworks (MOFs) hold great promise for versatile and impactful applications. However, challenges remain in achieving rapid, reproducible syntheses, obtaining fully activated materials with permanent porosity, and developing a deeper understanding of their structure-property relationships. This thesis explores the synthesis, activation, structural diversity, and multifunctionality of MOFs, highlighting how their fundamental properties can be leveraged to address environmental challenges. Here, we will focus on CO2 capture and the detection and removal of arsenic from water, reducing the risks to human health and ecosystems. In Chapter 1, we outline the motivation for this work and the associated challenges of MOFs and possible environmental applications. In Chapter 2, we present a joint experimental, computational, and high-throughput approach to improve on the traditional "trial and error" method of MOF synthesis optimization. In this project, we optimize the synthesis conditions of an aluminum (Al)-porphyrin-based MOF (i.e., Al-PMOF), promising for CO2 capture. Despite the challenges in synthesizing porphyrin-based MOFs, this approach proved to be efficient. It allowed us to translate the traditional 16-hour hydrothermal synthesis to a microwave-based method, yielding high crystallinity, effective CO2 capture, and a much shorter reaction time (50 minutes) with fewer than 50 iterations. In Chapter 3, we focus on preparing MOFs for functional use, with emphasis on their activation. We extend our study beyond permanent porosity and explore how activation influences the optical properties of a bismuth (Bi)-ellagate MOF (i.e., SU-101), with promising features for photocatalysis. We investigate several solvent exchange procedures, followed by thermal and vacuum activation, to expose the MOF's reactive under-coordinated metal sites. This improves its absorption in the visible range and alters the photoluminescence (PL) spectra, demonstrating that solvent removal plays a key role in shaping the material's optoelectronic properties. Subsequently, in Chapter 4, we perform a systematic study on pyrene-based-MOFs (i.e., 1,3,6,8-tetrakis(p-benzoic acid)pyrene (TBAPy)), where we synthesize structures with different metals (i.e., Al, Ga, Sc, and In). The orthorhombic system shows a parallel stacking of the ligand, creating favorable CO2 binding sites, but the metal center affects this stacking, and therefore the uptake. Crystallography shows secondary phases that influence adsorption; accounting for them improves prediction accuracy and guides material design. Finally, in Chapter 5, we investigate a porous coordination network (PCN)-222, a zirconium (Zr)-porphyrin MOF. We shaped the MOF's powder into beads using polyethersulfone (PES) and studied the composite for arsenate capture. We show the material's ability to reduce the arsenic concentration below the World Health Organization (WHO) limit of 10 ppb. Moreove
