Robust Mixed-Ligand Ni(II)-framework With Pore-Engineered Lewis Acid-Base Sites for Size-selective and One-Pot Mild Synthesis of Bioactive 4H-Pyrans.

The rational integration of antagonistic catalytic sites within robust porous architectures remains a critical challenge for sustainable multicomponent reactions to synthesize pharmacologically active molecules. Herein, we report a thermo-chemically stable, mixed-ligand Ni(II)-based pillar-layered metal-organic framework (MOF), featuring activation-induced open metal sites and pore-confined Lewis basic centres. This bifunctional framework acts as an efficient heterogeneous catalyst for one-pot Knoevenagel-Michael multicomponent reactions, enabling the rapid synthesis of structurally diverse 2-amino-3-cyano-4H-pyrans under mild conditions with low catalyst loading. The synthesis of 4H-pyrans is promoted by the synergistic interplay between Lewis acidic metal centres and framework-integrated basic sites, as corroborated by control experiments and analyte-responsive emission modulation. The protocol accommodates twenty-six electronically diverse substrates and affords bioactive pyran derivatives in excellent yields. Notably, the confined pore environment imparts distinct size-selectivity, restricting bulky substrates and demonstrates molecular-dimension-controlled catalysis. The framework exhibits remarkable recyclability, structural robustness, and negligible metal leaching, outperforming many reported catalytic systems. Importantly, eight 4H-pyrans were structurally confirmed in their purest form by single-crystal X-ray diffraction, alongside other spectroscopic characterizations. This work highlights a rational platform for designing bifunctional MOF catalysts to promote green organic synthesis through the synergistic cooperation of antagonistic functionalities confined within porous architectures.