Photoluminescence (PL) in two-dimensional (2D) materials underpins quantum photonics and optoelectronics by revealing recombination kinetics and defect energetics. However, controllable defect-dominated peak shifts and deterministic tuning of the emission wavelength remain challenging to achieve in PL. Hence, we investigate PL engineering in 2DMs, including hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDs). First, an approach is developed for precise adjustment of the defect structure of hBN to achieve the modification of zero-phonon lines (ZPLs) in PL. By regulating the carbon concentration from 0.0005 at% to 0.082 at% in Cu substrates during chemical vapor deposition (CVD) process, we engineer the defect structure from CB (carbon substituted at the boron site) to C₂B-CN (carbon doped into two boron sites and one nitrogen site) in hBN, which produces a specific shift in the ZPL from 600-610 nm to 630-640 nm. These adjustments in the emission spectrum are further supported by density functional theory (DFT) results, indicating alterations in the band structure, vibrational properties, and electronic transitions. Second, we show that controllable selenium-vacancy populations in molybdenum diselenide (MoSe₂) modulates the excitonic PL peak position, enabling a well-defined distribution of exciton types and the dominated emission induced by defect bound excitons combination. Through the structured-defect modification and PL engineering, emission properties can be well-customized, opening avenues for incorporating advanced materials in on-chip quantum devices, representing a significant advancement in quantum computing.