This doctoral thesis presents a comprehensive exploration of a series of advanced materials utilizing the power of a number of ultrafast spectroscopic techniques. The investigation into aggregation-induced emission enhancement (AIEE) delves into benzodiazole donor–acceptor–donor (D–A–D) molecules, revealing a notable increase in fluorescence lifetime from 746 ps at 1x10-11 M to 2.48 ns at 2.0x10-3 M. Through intricate structural modifications, such as the acetylene bond and sulfur atom, this study elucidates the mechanisms driving fluorescence enhancement, paving the way for tailored chromophores optimized for light-harvesting applications. 

This work also investigates how intramolecular ring rotation impacts the photoluminescence (PL) and excited-state lifetime of two organic free-linkers. Comprehensive analysis, including steady-state and time-resolved spectroscopy and TD-DFT calculations, reveals distinct photophysical behaviors for each linker. For Linker 1, complex kinetics and solvent-dependent PL changes are linked to intramolecular twisting. Linker 2's rigidity due to steric hindrance limits nonradiative decay, enhancing PL. Comparing meta and ortho amine positions, the meta linker shows a twofold increase in excited-state lifetime, attributed to restricted twisting. These findings are crucial for optimizing organic emitters in metal-organic frameworks (MOFs) for sensing and light-emitting applications. 

The thesis also investigates the innovative fusion of mixed-matrix membranes (MMMs) comprising MOFs and emissive polymers. Notably, MMMs demonstrate an exceptional modulation bandwidth of around 80 MHz, surpassing conventional phosphors and the interfacial energy transfer between MOF and polymer enhanced the data rates from 132 Mb/s to 215 Mb/s in optical wireless communication systems. Through a combination of experimental techniques and advanced density functional theory calculations, this study elucidates the mechanisms driving efficient energy transfer from luminescent MOFs to polymers, highlighting the potential of MMMs to revolutionize optical communication technologies. 

Lastly, the research addresses experimental challenges in tracking ultrafast hole injection dynamics at interfaces, particularly focusing on copper thiocyanate (CuSCN). Femtosecond mid-infrared (IR) spectroscopy reveals a rapid formation (< 168 fs) and blue spectral shift of the CN stretching vibration from 2118 cm-1 for CuSCN alone to 2180 cm-1 for PM6/CuSCN. These results offer direct evidence of hole injection at the PM6/CuSCN interface, presenting a powerful investigative approach with implications for interfacial chemistry and solar cell research communities. 

Ultimately, this thesis advances our understanding of fundamental photophysical processes and their applications across diverse technological domains. The findings underscore the importance of structural modifications, energy transfer mechanisms, and interfacial dynamics in light-conversion materials for both real-world applications and fundamental understanding of photo-physical and photochemical processes that could pave the way for future advancements in optoelectronic applications of complex systems including MOFs and polymers.