This chapter covers the various synthetic methods in ultrasmall size of metal nanoparticles (NPs) and characterization of zirconium (Zr)-based metal-organic frameworks (UiO-MOFs) for the application of CO2 capture and heterogeneous catalysis. It discusses the major goals to achieve the synthesis of metal-organic frameworks of Zr family such as UiO-66, UiO-66-NO2, UiO-66-NH2, and UiO-67 with high crystallinity, high-surface area, and increased yield using different parameters such as decreased reaction time, temperature, the role of modulators, solvent system, etc. The chapter also furnishes details of how various favorable and deleterious phases evolve to tune the synthesize of metal NPs in ultrasmall size and its characterization using various spectroscopic and analytical methods such as infrared, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, inductively coupled plasma, nuclear magnetic resonance, etc. This chapter also deals with the application of CO2 capture and heterogeneous catalysis in various fields of science. The chapter will enable the reader to identify and relate to get the ideas for design, and tune synthesis of metal NP in MOFs porous structures for wide range of application in science and engineering.