Pd(II)-anchored conjugated covalent organic frameworks for hydrolytic cleavage of CS₂ and unlocking heterogeneous...

Porous catalysts capable of hydrolyzing carbon disulfide (CS₂) and carbonyl sulfide (COS) at room temperature are important for petrochemical and environmental applications. Herein, we report the first Pd(II)-anchored conjugated covalent organic frameworks (COFs 2a and 2b) that catalyze CS₂ and COS hydrolysis at 25 °C. Under standard conditions, both porous catalysts generated CO₂, protons (H⁺) and sulfide (HS^-) from CS₂ hydrolysis. The catalytic efficiencies of COFs 2a-2b are 2.638 and 4.028 μmol g^-1h^-1, respectively. In this process, the sulfide ion (HS^-) coordinates to Pd(II) centers in the porous catalyst, forming the intermediates COFs 3a-3b. Subsequently, upon oxidation with concentrated nitric acid, the robust COFs 2a-2b catalyze the "one‑pot" hydrolytic cleavage of carbon disulfide with activities of 13.506 and 14.787 μmol g^-1h^-1, respectively, which are approximately six times higher than those reported for dinuclear Pd(II) complexes. Two catalysts are readily recovered by treatment with concentrated nitric acid and exhibit excellent recyclability, retaining more than 80 % of their initial activity after five cycles. In situ DRIFTS, model reaction studies, and DFT calculations support a mechanism in which hydroxide (OH^-) sequentially attacks the carbon centers of Pd‑coordinated CS₂ and COS to generate readily decomposable thiocarbonate intermediates (di‑ and monothiocarbonate anions), thereby promoting CS bond cleavage and CO bond formation. Together, these results clarify the structure-activity relationships and reaction mechanism of COF‑supported Pd(II) catalysts.