A multi-functionalized MOF with unique molecular-sized pockets for excellent lead(II) removal and selective separation of C3H8/CH4

Abstract

Design and synthesis of metal-organic frameworks (MOFs) with functional pore environments are of critical significance for the development of the porous adsorbents to solve energy and environmental crises. Herein, we utilized the structural and coordinated characteristics of adenine (HAD) ligands to develop a multi-functional MOF material (JLU-MOF68) with unique molecular-sized pockets for gas separation and Pb2+ removal. Benefiting from the internal surface environment and the size of 4.6–5.9 Å of the molecular pockets, JLU-MOF68 exhibited ultrahigh C3H8/CH4 selectivity coupled with the relatively high adsorption capacity of C3H8. Both N sites and extraframework organic cations were conducive to the adsorption of Pb2+ through weak chemical coordination and ion exchange, respectively. The activated JLU-MOF68 showed not only an ultrahigh Pb2+ adsorption capacity of 805 mg g−1, but also exceptionally high Pb2+ removal efficiency under the condition of different pH and coexisting ions. Moreover, the adsorbent can be reused at least five times, and the removal efficiency remains almost constant after five cycles. Therefore, JLU-MOF68 had a wide potential application for the C3H8/CH4 selective separation and capture of Pb2+.