Discarded textiles have become a significant environmental and social challenge worldwide. Each year, millions of tons of clothing end up in landfills or incinerators, exacerbating waste management issues. Polyester fibers—also known as poly(ethylene terephthalate) (PET) fibers—account for over 50% of global fiber production and make up a substantial share of textile waste. However, existing PET recycling efforts mainly focus on plastic bottles, leaving polyester textiles largely overlooked. This dissertation explores upcycling strategies for discarded polyester textiles, focusing on transforming these materials into value-added products through two key approaches. This dissertation particularly focuses on developing approaches that do not require the separation of impurities from raw textile materials—a process that often complicates textile recycling. The first approach investigates the synthesis of metal-organic frameworks (MOFs) using linkers obtained from depolymerization of polyester textiles. The second approach involves producing electrospun nanofibrous membranes (NFMs) using polyester textiles as polymer sources. The synthesized MOFs and NFMs demonstrated potential applications in superhydrophobic textile coating and oil sorption, highlighting their environmental and industrial relevance. The opening chapter provides the necessary background and introduction for understanding the MOF synthesis and electrospinning using discarded polyester textiles. Chapter 2 introduces the synthesis of CuBDC MOFs, where dyed polyester textiles are depolymerized into Na2BDC linkers, which are then used to construct CuBDC structures through their reaction with a specifically designed copper precursor. Chapter 3 continues by exploring the synthesis of UiO-66 MOFs on textile substrates, utilizing a polyester/spandex blend as a linker source to fabricate superhydrophobic UiO-66 textile coatings. The second approach, focused on the production of electrospun NFMs, is detailed in Chapter 4 and 5, which chronologically follow the steps taken to investigate the properties and applicability of these NFMs. Chapter 4 examines the structural properties of electrospun NFMs produced from polyester textiles, comparing them with those made from PET bottles. Chapter 5 demonstrates the oil sorption capability of electrospun NFM sorbents fabricated from three different discarded materials—polyester/spandex blends, polyester textiles, and PET bottles. The dissertation concludes with Chapter 6, which summarizes the research findings, suggests paths for future investigation, and offers closing thoughts.