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Maintaining the configuration of a light-responsive metal–organic framework: LiYGeO4:Bi³⁺-incorporation-induced long-term bending through short-time light irradiation
Summary:
The authors from Nanjing Tech University developed a PCN-250/LiYGeO4:Bi³⁺ composite (PCN-PLM) that exhibits persistent photo-modulation of CO₂ capture. After only 10 min UV (254 nm) excitation, the composite sustains 365 nm emission for ≥6 h, enabling a 14.6 % reversible decrease in CO₂ uptake without continuous irradiation.
Background:
1. Prior work introduced azobenzene ligands into MOFs to create light-responsive adsorbents, but structural reversion upon light-off limits practical use.
2. The authors proposed embedding an inorganic persistent luminescent material (PLM, LiYGeO4:Bi³⁺) into PCN-250 to prolong the “bent” state of azobenzene linkers, thus solving the need for sustained illumination.
Research Content:
1. Synthesis
• PCN-250 was solvothermally grown from Fe₂Co(μ₃-O)(CH₃COO)₆ clusters and ABTC ligand.
• LiYGeO4:Bi³⁺ was prepared via high-temperature solid-state reaction, then co-solvothermally incorporated into PCN-250 to yield PCN-PLM-n (n = 1–3, 21.3–52.7 wt % PLM).
2. Characterizations
1) BET: PCN-250 1214 m² g⁻¹, 0.55 cm³ g⁻¹; decreases to 683 m² g⁻¹, 0.27 cm³ g⁻¹ for PCN-PLM-3, yet microporosity is retained.
2) SEM/TEM: PCN-250 shows ~20 µm regular polygons; PLM nanoparticles are uniformly dispersed without altering morphology.
3) Optical tests: UV-Vis confirms azobenzene trans→cis transition under 365 nm; PLM exhibits persistent 365 nm emission for >6 h after 254 nm excitation; TG/DTG verifies thermal stability up to 420 °C.
3. Application
CO₂ adsorption (273 K, 1 bar): PCN-PLM-2 capacity drops from 84.8 to 72.7 cm³ g⁻¹ (14.6 % change) after 10 min 254 nm irradiation; 80 % reversibility maintained after four cycles.
4. Mechanism
UV (254 nm) charges LiYGeO4:Bi³⁺, which slowly releases 365 nm light. This sustains the cis-bent configuration of ABTC ligands, shrinking pore aperture and lowering CO₂ uptake. When PLM emission decays, ligands revert to trans, restoring capacity.
Outlook:
The study demonstrates a practical strategy to decouple light activation from continuous irradiation in photo-responsive MOFs, paving the way for energy-efficient, remotely controlled gas-separation processes.
Maintaining the configuration of a light-responsive metal–organic framework: LiYGeO4:Bi³⁺-incorporation-induced long-term bending through short-time light irradiation
Authors: Wen-Juan Zhang, Li Zheng, Shi-Chao Qi*, Jia-Xin Li, Ding-Ming Xue, Xiao-Qin Liu, Lin-Bing Sun*
DOI: 10.1039/D3TA01241G
Link: https://pubs.rsc.org/en/content/articlelanding/2023/ta/d3ta01241g
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