Selective hydrogenation of detrimental 4-nitrophenol to desired 4-aminophenol over potent PtCo intermetallic nanoparticles entrapped within the pores of Cr-BDC MOFs

Abstract

Engineering of economical and stabilized precious metal based catalysts are crucial in recent ages to achieve the desirable catalytic performance as they tend to destabilize easily. Herein, Cr-BDC MOF was prepared that provides high surface area and pore volumes to evenly distribute, host, and stabilize the Pt and Co intermetallic nanoparticles (IMNs). Among these, the PtCo/Cr-BDC catalyst showed superior selective hydrogenation activity for 4-Nitrophenol (4-NP) to 4-Aminophenol (4-AP) as an exemplary reaction. A number of characterization techniques were carried out to study the influence of the Cr-BDC support and Co metal on the surface and bulk structural properties of active Pt metal species. The Cr-BDC support imparts uniform distributions while the Co metal species influenced the catalytic activity. The maximum conversion (99.3 %) of 4-NP to 4-AP was observed with PtCo/Cr-BDC in 2 min at a reaction rate constant (k) of 1.27 min−1 at room temperature, which is superior than Pt/Cr-BDC (0.64 min−1) and Co/Cr-BDC (0.14 min−1). The superior hydrogenation activity was credited to the addition of electropositive Co species to Pt/Cr-BDC catalyst that synergistically interacts with active Pt species within the pores of Cr-BDC MOFs and making PtCo IMNs system. As a result of this synergistic interaction, new additional interfacial electrophilic and nucleophilic metallic sites are generated within the pores of MOFs, which enormously encourage the selective hydrogenation of lethal 4-NP to valued 4-AP. Besides, the PtCo/Cr-BDC catalysts revealed remarkable durability up to several repeated rounds, validating its real-world applicability.