Inter-cluster-linker-absence-enabled sub-Ångstrom pore modulation in a 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 a 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 in coordination bond length (approximately 2.3 Å for Cd(II)–N and approximately 2.1 Å for Cu(II)–N) to the size of secondary building blocks (approximately 6.5 × 6.5 × 6.7 ų for [Cd₈(TAZ)₉] and approximately 6.2 × 6.2 × 6.3 ų for [Cu₈(TAZ)₉]), and to the final MOF pore (approximately 5.5 Å for SNNU-98-Cd and approximately 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. SNNU-98-Cu is an ideal carbon capture material for practical applications due to its low-cost raw materials, easy scalablity in synthesis, ultra-high stability, and top-level selective adsorption ability as well as multi-scenario adaptability.