Ultrathin Metal-Organic Framework Nanosheets for Selective Photocatalytic C₂ H₂ Semihydrogenation in Aqueous Solution

The selective semihydrogenation of C₂ H₂ to C₂ H₄ in crude C₂ H₄ (with ~1 vol % C₂ H₂ contamination) is a crucial process in the manufacture of polyethylene. Comparing to conventional thermalcatalytic route with Pd as catalyst under high temperature with H₂ as hydrogen source, photocatalytic C₂ H₂ reduction reaction with H₂ O as hydrogen source can achieve high selectivity under milder conditions, but has rarely been reported. Here, we present a kind of ultrathin metal-organic framework nanosheets (Cu-Co-MNSs) that demonstrate excellent catalytic activities in the semihydrogenation of C₂ H₂ . Employing Ru(bpy)₃ ²⁺ as the photosensitizer, this catalyst attains a noteworthy turnover number (TON) of 2124 for C₂ H₄ , coupled with an impressive selectivity of 99.5 % after 12 h visible light irradiation. This performance is comparable to molecular catalysts and notably surpasses the efficiency of bulk metal-organic framework materials. Furthermore, Cu-Co-MNSs achieve a 99.95 % conversion of C₂ H₂ under industrial relevant conditions (1.10 % C₂ H₂ in C₂ H₄ ) with 90.3 % selectivity for C₂ H₄ over C₂ H₆ , demonstrating a great potential for polymer-grade C₂ H₄ production.