Home >
News > Toward Design Rules of Metal−Organic Frameworks for Adsorption Cooling: Effect of Topology on the Ethanol Working Capacity
Toward Design Rules of Metal−Organic Frameworks for Adsorption Cooling: Effect of Topology on the Ethanol Working Capacity
Summary:
The authors from Northwestern University (U.S.), Nanjing Tech University (China), and Toyota Research Institute of North America (U.S.) developed a series of zirconium-based metal-organic frameworks (Zr-MOFs) with varied topologies and pore sizes, achieving optimal ethanol adsorption capacities in adsorption cooling applications.
Background:
1. To address the issues of high energy consumption (10% of global electricity) and CO₂ emissions of conventional compression cooling systems, previous researchers explored adsorption cooling systems driven by waste/solar energy and tested porous adsorbents like activated carbons and MOFs. However, the systematic relationship between MOF structural properties and adsorption cooling performance remained unclear.
2. The authors proposed an innovative approach: selecting MOFs with identical Zr₆O₈ nodes and tetratopic carboxylate linkers but different topologies to isolate pore size effects, and identified optimal pore sizes for different cooling scenarios.
Research Content:
1.Synthesis:
The authors synthesized MOFs (PCN-223, NU-901/902, MOF-525, etc.) via literature methods. As-synthesized MOFs were washed with DMF/acetone (3 times each); MOF-525/PCN-223 were activated at 120°C overnight, while NU-1000/NU-901 etc. underwent HCl (8M)-DMF treatment (100°C, overnight) before activation.
2.Characterizations:
1) BET & Pore Size: N₂ sorption (77K) showed varied pore structures; MOF-525 had 1.8 nm cavity, PCN-223 0.8 nm, PCN-222 3.0 nm.
2) SEM: Hitachi SU8030 images (after OsO₄ coating, ~9 nm) showed distinct morphologies of NU-901, MOF-525, etc.
3) Other Tests: PXRD (STOE-STADIMP, CuKα, λ=1.54056Å) confirmed crystallinity; ethanol sorption (Micromeritics 3Flex) measured uptake (e.g., MOF-525: 0.51 g/g refrigeration capacity).
3.Application:
The MOFs were tested in adsorption cooling (refrigeration, ice-making, heat pump). MOF-525 exhibited the highest working capacity: 0.51 g/g (gravimetric) and 0.47 ml/ml (volumetric) for refrigeration, 0.20 g/g and 0.19 ml/ml for ice-making.
4.Mechanism:
GCMC simulations (RASPA) and DFT (VASP) revealed ethanol adsorbs via H-bonding with Zr₆ nodes first; micropores fill at low pressure, mesopores at higher pressure. Medium pores (~2 nm) balance low-pressure uptake and saturation loading, optimizing capacity.
Outlook:
This research clarifies MOF topology-pore size-ethanol adsorption relationships, identifies optimal pore sizes (1.5 nm for ice-making, ~2 nm for refrigeration, 3-4 nm for heat pumps), and provides design rules for high-performance MOF adsorbents in adsorption cooling, promoting energy-efficient cooling system development.
Toward Design Rules of Metal−Organic Frameworks for Adsorption Cooling: Effect of Topology on the Ethanol Working Capacity
Authors: Haoyuan Chen, Zhijie Chen, Lin Zhang, Peng Li, Jian Liu, Louis R. Redfern, Shinya Moribe, Qun Cui, Randall Q. Snurr, Omar K. Farha
DOI: 10.1021/acs.chemmater.9b00062
Link: https://pubs.acs.org/doi/10.1021/acs.chemmater.9b00062
The above review is for academic progress sharing. For any errors or copyright issues, please contact us for correction or removal.
