Metal organic frameworks(MOFs)have emerged as promising candidates for atmospheric water harvesting due to their high porosity and tunable functionality.Among diverse MOFs,MOF-303 has demonstrated excellent water adso...Metal organic frameworks(MOFs)have emerged as promising candidates for atmospheric water harvesting due to their high porosity and tunable functionality.Among diverse MOFs,MOF-303 has demonstrated excellent water adsorption capacity,rapid desorption kinetics and structural stability.Nevertheless,its practical application is still limited by the time-consuming synthesis process and difficultiesin morphological control.To overcome these challenges,a surfactant-mediated microwaveassisted strategy was proposed.Compared to conventional heating methods,microwave irradiation reduced the reaction duration from 24 h to 1 h with a 13%increase in product yield(from 76%to 89%).However,the accelerated nucleation under microwave irradiation resulted in smaller crystal dimensions(from 50 nm±10 nm to 35 nm±10 nm),therefore inducing severe particle agglomeration.To mitigate this morphological drawback,systematic investigations were conducted to evaluate the effects of surfactants’species on crystal growth.Among the selected surfactants,poly(sodium-p-styrene sulfonate)(PSS)was identifiedas an effective morphology-directing agent,achieving uniform crystal sizes with improved monodispersity through preferential adsorption on specificcrystallographic planes of the MOF.Subsequent optimization of synthetic conditions,including temperature(120-160℃),reaction time(15 min^(-1) h),and surfactant concentration,yielded MOF-303 with a yield of 96.37%,with particle uniformity of(35 nm±10 nm)and predominantly blocky crystal morphology.Water adsorption measurements confirmedthat the surfactant-modifiedMOF-303 retained comparable performance to the surfactant-free counterpart,with a maximum capacity(water/MOF)of 0.214 g·g^(-1) at 35%RH.This study establishes a scalable and tunable synthetic protocol for MOF-303,providing critical insights into microwave-accelerated crystal engineering.展开更多
Aiming at the problem that the traditional inter-system double-difference model is not suitable for non-overlapping signal frequencies,we propose a new inter-system double-difference model with single difference ambig...Aiming at the problem that the traditional inter-system double-difference model is not suitable for non-overlapping signal frequencies,we propose a new inter-system double-difference model with single difference ambiguity estimation,which can be applied for both overlapping and non-overlapping signal frequencies.The single difference ambiguities of all satellites and Differential Inter-System Biases(DISB)are first estimated,and the intra-system double difference ambiguities,which have integer characteristics,are then fixed.After the ambiguities are successfully fixed,high-precision coordinates and DISB can be obtained with a constructed transformation matrix.The model effectively avoids the DISB parameter filtering discontinuity caused by the reference satellite transformation and the low precision of the reference satellite single difference ambiguity calculated with the code.A zero-baseline using multiple types of receivers is selected to verify the stability of the estimated DISB.Three baselines with different lengths are selected to assess the positioning performance of the model.The ionospheric-fixed and ionospheric-float models are used for short and medium-long baselines,respectively.The results show that the Differential Inter-System Code Biases(DISCB)and Differential Inter-System Phase Biases(DISPB)have good stability regardless of the receivers type and the signal frequency used and can be calibrated to enhance the strength of the positioning model.The positioning results with three baselines of different lengths show that the proposed inter-system double-difference model can improve the positioning accuracy by 6–22%compared with the intra-system double-difference model which selects the reference satellite independently for each system.The Time to First Fix(TTFF)of the two medium-long baselines is reduced by 30%and 29%,respectively.展开更多
基金financial support from the National Natural Science Foundation of China (22222809, 22308250)the fellowship of the China Postdoctoral Science Foundation(2022TQ0232, 2022M722365)the support from Haihe Laboratory of Sustainable Chemical Transformations
文摘Metal organic frameworks(MOFs)have emerged as promising candidates for atmospheric water harvesting due to their high porosity and tunable functionality.Among diverse MOFs,MOF-303 has demonstrated excellent water adsorption capacity,rapid desorption kinetics and structural stability.Nevertheless,its practical application is still limited by the time-consuming synthesis process and difficultiesin morphological control.To overcome these challenges,a surfactant-mediated microwaveassisted strategy was proposed.Compared to conventional heating methods,microwave irradiation reduced the reaction duration from 24 h to 1 h with a 13%increase in product yield(from 76%to 89%).However,the accelerated nucleation under microwave irradiation resulted in smaller crystal dimensions(from 50 nm±10 nm to 35 nm±10 nm),therefore inducing severe particle agglomeration.To mitigate this morphological drawback,systematic investigations were conducted to evaluate the effects of surfactants’species on crystal growth.Among the selected surfactants,poly(sodium-p-styrene sulfonate)(PSS)was identifiedas an effective morphology-directing agent,achieving uniform crystal sizes with improved monodispersity through preferential adsorption on specificcrystallographic planes of the MOF.Subsequent optimization of synthetic conditions,including temperature(120-160℃),reaction time(15 min^(-1) h),and surfactant concentration,yielded MOF-303 with a yield of 96.37%,with particle uniformity of(35 nm±10 nm)and predominantly blocky crystal morphology.Water adsorption measurements confirmedthat the surfactant-modifiedMOF-303 retained comparable performance to the surfactant-free counterpart,with a maximum capacity(water/MOF)of 0.214 g·g^(-1) at 35%RH.This study establishes a scalable and tunable synthetic protocol for MOF-303,providing critical insights into microwave-accelerated crystal engineering.
基金This work was jointly supported by the National Key Research Program of China Collaborative Precision Positioning Project(No.2016YFB0501900)the National Natural Science Foundation of China(Grant No.41774017).
文摘Aiming at the problem that the traditional inter-system double-difference model is not suitable for non-overlapping signal frequencies,we propose a new inter-system double-difference model with single difference ambiguity estimation,which can be applied for both overlapping and non-overlapping signal frequencies.The single difference ambiguities of all satellites and Differential Inter-System Biases(DISB)are first estimated,and the intra-system double difference ambiguities,which have integer characteristics,are then fixed.After the ambiguities are successfully fixed,high-precision coordinates and DISB can be obtained with a constructed transformation matrix.The model effectively avoids the DISB parameter filtering discontinuity caused by the reference satellite transformation and the low precision of the reference satellite single difference ambiguity calculated with the code.A zero-baseline using multiple types of receivers is selected to verify the stability of the estimated DISB.Three baselines with different lengths are selected to assess the positioning performance of the model.The ionospheric-fixed and ionospheric-float models are used for short and medium-long baselines,respectively.The results show that the Differential Inter-System Code Biases(DISCB)and Differential Inter-System Phase Biases(DISPB)have good stability regardless of the receivers type and the signal frequency used and can be calibrated to enhance the strength of the positioning model.The positioning results with three baselines of different lengths show that the proposed inter-system double-difference model can improve the positioning accuracy by 6–22%compared with the intra-system double-difference model which selects the reference satellite independently for each system.The Time to First Fix(TTFF)of the two medium-long baselines is reduced by 30%and 29%,respectively.
