Water, the most fundamental source of life, is contaminated by various organic pollutants, especially organic dyes from the dying industry. The photocatalytic degradation of malachite green (MG) was studied using a zinc-based metal-organic framework (Zn-BTC MOF) and ZnO. Thermally decomposing Zn-MOF synthesized ZnO and its structural and optical properties were analyzed using various spectroscopic techniques. This article focuses primarily on the wavelength-dependent photoluminescence properties of Zn-MOF and ZnO materials and their role in the photocatalytic degradation of MG dye in water. Zn-MOF and ZnO photocatalysts exhibited a photodegradation efficiency of approximately 99% after 40 min of visible light exposure. Based on kinetic experiments, the degrading efficiency of these catalysts followed pseudo-first-order reaction kinetics with a correlation of R2 = 0.99 and a rate constant of 0.031 min−1. This manuscript is helpful to researchers working on ZnO and Zn-MOF materials for photocatalytic and environmental applications.