Inter-Cluster-Linker-Absence-Enabled Sub-Ångstrom Pore Modulation in Metal-Organic Framework for Multi-Scenario CO2 Capture

Abstract

Ultrafine aperture control of carbon capture adsorbents is first and foremost important but inscrutable. Herein an inter-cluster-linker-absence-enabled sub-Ångstrom pore modulation strategy is proposed through the efficient transitivity of coordination bonds in metal-organic framework (MOF). The feasibility of this strategy is well-demonstrated in SNNU-98-M materials composed of directly-connected [M8(TAZ)9] (M = Cd or Cu, TAZ = tetrazolate) triangular prism clusters. The removal of inter-cluster linkers effectively transfers the difference of coordination bond length (~2.3 Å for Cd(II)-N and ~2.1 Å for Cu(II)-N) to the size of secondary building blocks (~6.5 × 6.5 × 6.7 Å3 for [Cd8(TAZ)9] and ~6.2 × 6.2 × 6.3 Å3 for [Cu8(TAZ)9]), and to the final MOF pore (~5.5 Å for SNNU-98-Cd and ~5.1 Å for SNNU-98-Cu). Rational and hyperfine pore control together with optimized Lewis basic N sites endow SNNU-98-M with benchmark multi-scenario CO2 capture performance varying from binary flue gas (CO2/N2) to ternary biogas (CO2/CH4/N2) and even to quinary coal gas (CO2/CH4/N2/CO/H2) mixtures by a one-step process. Low-cost raw materials, easy scalablity in synthesis, ultra-high stability, top-level selective adsorption ability as well as multi-scenario adaptability make SNNU-98-Cu ideal carbon capture material for practical applications.