Chowdhury Sumanta, Sharma Abhishek, Das Partha Pratim, Rathi Preeti, Siril Prem Felix
School of Chemical Sciences and Advanced Materials Research Centre, Indian Institute of Technology Mandi, Mandi-175005, Himachal Pradesh, India.
School of Physics and CRANN Institute, Trinity College Dublin, Dublin 2, Ireland.
J Colloid Interface Sci. 2024 Jul;665:988-998. doi: 10.1016/j.jcis.2024.03.077. Epub 2024 Mar 13.
In applications utilizing Covalent Organic Frameworks (COFs) for adsorption, the interplay between crystallinity (vis-à-vis surface area) and active sites still remains ambiguous. To address this, the present study introduces three isoreticular COFs-COP-N18 (covalent organic polymer with short-range order), COF-N18 (COF having long-range order), and COF-N27 (semicrystalline COF with pyridyl heteroatoms)-to explore this duality. Through systematic variations in structural order, pore volume, and pore-wall nitrogen content, we aim to establish a structure-activity relationship (SAR) for these COFs via adsorption and catalysis, using CO and I as probes. Our investigation highlights the positive influence of crystallinity, surface area, and pore volume in adsorption as well as catalysis. However, the presence of heteroatoms manifests complex behavior in CO adsorption and CO cycloaddition reactions with epoxides. COF-N18 and COF-N27 showed comparable CO uptake capacities at different temperatures (273, 293, and 313 K) and ∼1 bar pressure. Additionally, CO cycloaddition reactions were performed with substrates possessing different polarities (epichlorohydrin, 1,2-epoxydodecane) to elucidate the role of COF surface polarity. Further investigation into iodine adsorption was performed to understand the impact of COF structural features on the modes of adsorption and adsorption kinetics. Improvements in COF-crystallinity results in faster average iodine uptake rate at 80% (K = 1.79 g/h) by COF-N18. Whereas, heteroatom doping slows down iodine adsorption kinetics (0.35 g/h) by prolonging the adsorption process up to 72 h. Overall, this study advances our understanding of COFs as adsorbents and catalysts, providing key insights into their SAR while emphasizing structural fine-tuning as a key factor for impactful environmental applications.
在利用共价有机框架（COF）进行吸附的应用中，结晶度（相对于表面积）与活性位点之间的相互作用仍不明确。为了解决这个问题，本研究引入了三种等规COF——COP-N18（具有短程有序的共价有机聚合物）、COF-N18（具有长程有序的COF）和COF-N27（具有吡啶基杂原子的半结晶COF）——来探究这种二元性。通过系统改变结构有序度、孔体积和孔壁氮含量，我们旨在以CO和I为探针，通过吸附和催化为这些COF建立结构-活性关系（SAR）。我们的研究突出了结晶度、表面积和孔体积在吸附以及催化方面的积极影响。然而，杂原子的存在在CO吸附以及CO与环氧化物的环加成反应中表现出复杂的行为。COF-N18和COF-N27在不同温度（273、293和313 K）和约1 bar压力下表现出相当的CO吸附容量。此外，还使用具有不同极性的底物（环氧氯丙烷、1,2-环氧十二烷）进行了CO环加成反应，以阐明COF表面极性的作用。进一步研究了碘吸附，以了解COF结构特征对吸附模式和吸附动力学的影响。COF-N18的COF结晶度提高导致在80%时平均碘吸收速率更快（K = 1.79 g/h）。而杂原子掺杂通过将吸附过程延长至72 h减缓了碘吸附动力学（0.35 g/h）。总体而言，本研究推进了我们对COF作为吸附剂和催化剂的理解，为其结构-活性关系提供了关键见解，同时强调结构微调是实现有效环境应用的关键因素。
