A functionalized Hf(IV)-based metal-organic framework (MOF) was synthesized, characterized, and successfully employed as a highly sensitive and selective fluorometric sensor for (1,1-diamino-2,2-dinitroethylene) FOX-7, which is a significant nitro explosive. The fluorescent sensor (MOF) denoted CSMCRI-KNC', exhibited turn-off fluorescence signal towards FOX-7 in water medium even in the presence of other potentially competitive explosives. The limit of detection for FOX-7 is fairly low (189 nM), the response time is too fast (<20 s) and the mechanism is based on photo-induced electron transfer (PET). The sensing medium (water), detection time, sensitivity, and selectivity give this sensor a special place in the fluorescence-based sensor field. Additionally, the MOF was utilized as an efficient, recyclable, and heterogeneous catalyst for the Knoevenagel condensation between barbituric acid and aromatic aldehydes in the presence of ethanol in an eco-friendly reaction medium. The attractive features of the present catalytic methodology are mild reaction conditions, short reaction time, high atom economy, and tolerance of various functional moieties. The catalyst could be recovered and reused successively without any remarkable loss in the catalytic activity. Moreover, the “hot filtration method (Sheldon's test)” has also been established to ensure the heterogeneity of the catalyst. The plausible mechanism of the catalysis is well presented.