High-value Products Research Articles

Synthesis of biocompatible hydroxyapatite from quail eggshell, oyster shell, and periwinkle snail shell

This study focuses on the synthesis of hydroxyapatite (HA, Ca10(PO4)6(OH)2) from calcium carbonate (CaCO3)-rich quail eggshells, oyster shells, and periwinkle snail shells (Filopaludina bengalensis) through the use of the wet precipitation method. The methodology involved calcining the shell waste to convert CaCO3 to calcium oxide (CaO), undergoing hydration, and reacting with phosphoric acid (H3PO4) to synthesize HA. The results indicated that periwinkle snail shells had the highest percent yield of HA at 92.12%, followed closely by quail eggshells at 92.01%, and oyster shells at 73.65%. For producing CaO, oyster shells provided the highest percent yield of CaO at 103.72%, followed by quail eggshells at 98.6% and periwinkle snail shells at 92.09%. The synthesized HA exhibited high biocompatibility, which is crucial for its potential applications in medical fields such as bone replacement and regeneration. The X-ray diffraction (XRD) analysis confirmed the successful synthesis of high-quality HA, with characteristic peaks indicative of excellent crystallinity and purity and near identicality to the standard XRD pattern of HA of ICDD 9-432 and the XRD pattern of successfully synthesized HA in other studies, indicating high biocompatibility. The research highlights the potential of recycling food waste, specifically shell waste, into valuable biomaterials. This not only addresses environmental concerns but also supports sustainable practices in the food industry. Moreover, the study contributes to advancements in biomaterials for medical applications, emphasizing the viability of utilizing organic waste for high-value products. By transforming food waste into useful medical materials, this research offers promising solutions for waste management and resource utilization, particularly within Thailand's ecological and industrial framework.

Conceptual Design and Economic Optimization of Different Valorization Routes for Orange Peel Waste: The Application of the Biorefinery Concept for an Integral Use of Raw Material

Biorefineries are novel biotechnological routes designed to generate sustainable processes from renewable raw materials. The valorization of orange peel waste (OPW) provides high-value products based on their composition. The economic optimization of biorefineries through conceptual design and generation of superstructures based on the analysis of processing units is a topic of great interest. This work aimed to obtain the most profitable biorefinery through economic optimization strategies based on high-value-added products from OPW. Two stages were considered: The first stage consisted of the conceptual design of multiple OPW processing units (production of essential oil, mucic acid, phenolic compounds, biogas, among others). An OPW flow rate of 140 kg/h was selected as the base case. From the stand-alone units, a biorefinery superstructure (second stage) was designed. Finally, the units with the best mass and energy results were selected in order to maximize the net present value (NPV) and obtain an optimal biorefinery configuration. The results evidenced that the production of essential oil and biogas presented the best yields (2.61 mL and 0.028 m3 per kg OPW, respectively). This biorefinery configuration obtained an NPV of −7.7 mUSD from the base case. Through the evaluation of the different superstructure configurations, the combined production of essential oil, biogas, and mucic acid and a scale-up of over 22 times the base case generated the minimum processing scale. Under a Colombian context, the implementation of the biorefineries analyzed are promising since the minimum processing scale contemplated only 8.8% of the OPW production. Efforts to increase yields and decrease capital and operating expenses while keeping environmental impacts low should be pursued.

Purification of Crude Glycerol Recovered From Fish Processing Waste Biodiesel Process

Biodiesel and crude glycerol are byproducts of the esterification and transesterification reactions that occur between triglyceride molecules and alcohol in the presence of acid and base catalysts. Purification of crude glycerol is necessary to increase the economic sustainability of the biodiesel industry. This study was carried out for pre-treatment of crude glycerol sourced from fish processing waste during biodiesel manufacturing, treated through an acidification process using phosphoric acid (H3PO4), and then using further purification treatment with Jatropha curcas bio-adsorbent. Based on the measurement, the quantity of 0.1% phosphoric acid (H3PO4) solution was required to treat the crude glycerin. The reaction conditions include heating solution to 60°C and stirring it at 40 rpm for varying treatment periods such as 15, 30, 45, and 60 min. The crude glycerol's pH was adjusted to begin the acidification process, and soap was then converted into fatty acids and salts using phosphoric acid. The maximum purified glycerol yield of 76.6% by weight was obtained with treatment time of 15min using vacuum distillation at 120°C. The crude and purified glycerol’s density was measured as 1.013 g/mL and 1.001 g/mL, respectively. However, after bio-adsorbent treatment at temperature of 50°C and 10% loading weight of the Jatropha curcas bio-adsorbent, the best impurity elimination was accomplished in 15 min. The research findings demonstrated that, following acidification and bio-adsorbent treatments, the FFA% decreased from 2.82% to 2.24%, while its density increased from 1.002 g/mL to 1.032 g/mL, respectively. The purified glycerol properties were found in accordance with BS 2621-1979 standard, showing that the acidification method for purifying of crude glycerol, in conjunction with bio-adsorbent treatment is efficient in enhancing the glycerol purity. It also improves glycerol's application in generating high-value products that enhance revenue streams for the biodiesel production.

Intrinsic reactivity of stoichiometric IrO2(1 1 0) surface toward oxidative coupling of methane

This study investigates the oxidative coupling of methane on the IrO2(110) surface using TPRS simulations informed by DFT-derived data. We discover that the efficiency of the IrO2(110) surface in generating ethylene is strongly influenced by methane surface coverage. Our simulations reveal that the presence of surface hydroxyl group enhances the yield of C2+ species from methane oxidation, but this effect is counteracted at high methane coverages due to the accelerated formation of CH2OH. In addition, the study reveals that slight modifications in energy barriers at the branching point (C2H4 formation vs. CH2OH formation) significantly affect C2H4(g) production from the simulation, underscoring the importance of precise energetic data for accurate catalytic reaction predictions. The results have broader implications for reactions and catalysts where branching point selectivity determines high-value product yields. Thus, combining surface science with computational analysis is crucial for accurately determining energy profiles of key steps at the branching points.

Innovative Circular Biowaste Valorisation—State of the Art and Guidance for Cities and Regions

The management of the organic fraction of municipal solid waste (OFMSW), also called urban biowaste, and urban wastewater sludge (UWWS) represents a challenge for cities and regions, which want to adopt innovative urban bioeconomy approaches for their treatment and production of high-added-value products beyond the traditional anaerobic digestion (AD) and compost. This adoption is often restricted by the availability and maturity of technologies. The research object of this manuscript, based on the findings of EU Horizon 2020 project HOOP, is the identification of state-of-the-art circular technologies for material valorisation of OFMSW and UWWS, following a novel screening methodology based on the scale of implementation (tested at least at pilot scale). The screening resulted in 25 technologies, which have been compared and discussed under a multidisciplinary assessment approach, showing their enabling factors and challenges, their current or potential commercial status and their compatibility with the traditional technologies for urban biowaste treatment (composting and AD). The bioproducts cover market sectors such as agriculture, chemistry, nutrition, bioplastics, materials or cosmetics. Therefore, the results of this review help project promoters at city/region level to select innovative technologies for the conversion of OFMWS and UWWS into high value products.

Sensory Evaluation of Local Versus Imported Shrimp to Develop Marketing Strategies for United States Shrimp Producers

Shrimp is considered a high-value seafood product and the most consumed seafood in the Unites States. However, it is characterized by a short shelf-life. United States is heavily dependent on seafood imports, including shrimp, with more than 80 % of seafood being imported. The imported shrimp products are usually treated with preservatives such as phosphate to maintain quality, and possibly multiple rounds of freezing and thawing that can affect quality as well. Therefore, this study aimed to understand and compare the sensory/organoleptic characteristics of imported to US-based shrimp products. Additionally, nutritional values of the shrimp products were evaluated by analyzing their proximate composition. These results of the sensory panel showed a discrepancy between consumer stated preferences and actual behavior regarding shrimp products. While participants expressed a preference for preservative-free shrimp, as demonstrated acceptability was higher for imported shrimp containing preservatives. Proximate analysis showed farmed-raised shrimp to have significantly higher (p<0.05) protein content in comparison to wild–caught and imported shrimp. This can be a leverage to develop marketing strategies for locally produced shrimps that are not treated with preservatives.

New Biorefinery Approach for the Valorization of Fruit Processing Waste at a Local Scale: Pomegranate Pomace as Case Study

AbstractThe processing of fruit and vegetables generates globally high amount of organic waste, which is suitable to be valorized because of the chemistry it encloses. Conventional treatment methods for waste biomass generate low value products and cause climate altering emissions. Small biorefineries are valid alternatives for the sustainable waste biomass conversion, but their feasibility is strictly related to the use of low-energy process, and the market positioning of the final product. The present work provides an innovative approach for the green conversion of vegetable waste into high value product, with the aim to encourage the deployment of biorefinery at a local scale. It involves the enzymatic disassimilation of plant cell wall into chemicals with specific functions, and their recombination in form of emulsion, as a product prototype for food and cosmetic sector. To explain the biorefinery model, we applied it to pomegranate pomace, the residue from juicing, for the recovery of oil, pectin and antioxidant molecules via enzyme assisted extraction. The process left behind 30% of the initial solid waste. Finally, the dispersion of pomegranate oil into pomegranate pectin solution as emulsifier, brought to a novel emulsion, 98.9% waste-derived, further functionalizable with pomegranate exocarp hydrolysate with high antioxidant capacity. Graphical Abstract

Construction of a blockchain based cold chain logistics information platform for Gannan navel oranges to enhance transparency and efficiency

As a high-value agricultural product, the cold chain logistics management of Gannan navel oranges has global significance. Especially in Africa and Europe, food safety and supply chain quality are critical issues. However, the existing Gannan navel orange logistics information management system relies on traditional databases and information systems, with insufficient data sharing and transparency, affecting the overall coordination of the supply chain and customer satisfaction. In addition, the traditional system is vulnerable to hacker attacks and malicious tampering of data by insiders, resulting in serious economic losses and reputation damage. So the blockchain platform constructed in this study improves the transparency and traceability of logistics data through the SMART-PBFT algorithm of the alliance chain, which optimizes the logistics management process, improves the quality of logistics services, and reduces operating costs. It improves the logistics efficiency and data transparency of local agricultural products, and also provides a demonstrative case for the cold chain management of other high-value agricultural products around the world, with broad application potential and reference value.

Socio-Economic Characteristics of Producers and Economic Size Classes of Enterprises According To Typologies and Risk Attitudes in TR21 Region

The aim of this study was to determine the typologies of agricultural enterprises operating in the TR21 Region according to the Farm Accounting Data Network methodology and the risk attitudes of the producers. According to the typologies and risk attitudes of the enterprises, the socio-economic characteristics of the producers and the economic size classes of the enterprises were determined. As a result of sampling based on a 95% confidence interval and a 10% margin of error, the number of enterprises surveyed was determined as 334. While 63.77% of the enterprises were specialized in field crops, 25.45% engaged in mixed livestock and plant production. Additionally, 7.49% were specialized in pasture livestock and 3.29% were in the perennial plant farming group. In the enterprises examined, 55.09% of the producers were classified as risk-averse and 44.91% as risk-lover. Of the average land holdings, 71.25% was property and 28.75% was rented land. It was noteworthy that the land rental rate in risk-lover enterprises was higher than in risk-averse enterprises. It was concluded that risk-lover enterprises had higher production value in both plant production and animal production, and risk-averse enterprises were engaged with product and animal diversity as they avoided taking risks. On average, in risk-lover enterprises, 53.64% of the operating expenses were vegetative special expenses and 46.36% were animal special expenses. In risk-averse enterprises, the share of vegetative special expenses in total expenses was 47.15%, and the share of animal special expenses was 52.85%. Compared to the average of enterprises and all enterprise typologies, standard gross profit was found to be higher in risk-lover enterprises. In enterprise typology groups, the average ESU values of the enterprises varied between 10.88 and 33.80 ESU. According to enterprise typologies, risk-averse agricultural enterprises in specialized field crop farming and perennial plant farming were in the below-medium enterprise class, while other enterprise groups were in the above-medium enterprise class.

Efficient conversion of hemicellulose into high-value product and electric power by enzyme-engineered bacterial consortia

As an abundant agricultural and forestry biomass resource, hemicelluloses are hard to be effectively degraded and utilized by microorganisms due to the constraints of membrane and metabolic regulations. Herein, we report a synthetic extracellular metabolic pathway with hemicellulose-degrading-enzymes controllably displayed on Escherichia coli surface as engineered bacterial consortia members for efficient utilization of xylan, the most abundant component in hemicellulose. Further, we develop a hemicellulose/O2 microbial fuel cell (MFC) configuring of enzyme-engineered bacterial consortia based bioanode and bacterial-displayed laccase based biocathode. The optimized MFC exhibited an open-circuit voltage of 0.71 V and a maximum power density (Pmax) of 174.33 ± 4.56 µW cm−2. Meanwhile, 46.6% (w/w) α-ketoglutarate was produced in this hemicellulose fed-MFC. Besides, the MFC retained over 95% of the Pmax during 6 days’ operation. Therefore, this work establishes an effective and sustainable one-pot process for catalyzing renewable biomass into high-value products and electricity in an environmentally-friendly way.

Growth and metabolism regulation of cinnamic acid and its derivatives to Auxenochlorella pyrenoidosa

Auxenochlorella pyrenoidosa's industrial utility is closely associated with the concentration of high-value products. This study focuses on the effects of cinnamic acid (CA) and its derivatives, which known as secondary metabolites in higher plants and effective plant growth regulators, on the growth and metabolic profiles of A. pyrenoidosa. It was discovered that CA and its derivatives significantly enhance the biomass of A. pyrenoidosa under conditions of 10 mg/L over 48 h or 100 mg/L over 120 h. Cells treated with 10 mg/L CA exhibited lower oxidative stress and maintained robust metabolic activity. Metabolic pathways, including those for carbohydrates, lipids, small peptides, and cofactors, were stimulated, leading to the accumulation of a wide array of bio-products, notably high-value products such as α-linolenic acid, cis-4,7,10,13,16,19-docosahexaenoic acid (DHA), nicotinamide adenine dinucleotide plus hydrogen (NADH), glutathione, and vitamins B2/B3. This study demonstrates that CA and its derivatives are good nutritional enhancers for cultivating A. pyrenoidosa, highlighting their potential for broad application in biotechnological industries.

Non-Noble Metal Anchored 2D Covalent Organic Framework for Ambient CO2 Fixation to High-Value Compounds.

The catalytic functionalization of CO2 into high-value compounds comprises a promising approach to mitigate its atmospheric content and sustainable generation of fine chemicals. Herein, we report application of a crystalline, nano-porous 2D COF (ET-BP-COF) for utilization of CO2. The ET-BP-COF features a unique 2D kagome (kgm) topology composed of hexagonal and triangular 1D channels decorated with bipyridine sites, which were exploited for covalent anchoring of eco-friendly Cu(I) by post-synthetic method. The Cu(I) engrafted COF was applied as a recyclable catalyst for coupling CO2 with alkynes to generate two high-value compounds, α-alkylidene cyclic carbonates (α-ACCs) and 2-oxazolidinones. Notably, Cu(I)@ET-BP-COF demonstrated excellent catalytic performance for transforming propargylic amine and CO2 to 2-oxazolidinone, an essential building block for antibiotics. Besides, an efficient transformation of propargylic alcohols to generate α-ACCs, valuable commodity chemicals, has been achieved by utilizing carbon dioxide. Further, detailed theoretical simulations disclosed the insight mechanistic path of Cu(I) catalyzed coupling of CO2 with alkynes to produce 2-oxazolidinones and α-ACCs. Significantly, Cu(I)@COF was reusable for multiple cycles without losing framework rigidity and catalytic performance. This study showcases the potential application of ET-BP-COF for stable anchoring of eco-friendly metals as catalytic sites for effective utilization of CO2 to produce two high-value products.

Oxophilic Sn to promote glucose oxidation to formic acid in Ni nanoparticles.

The electrochemical glucose oxidation reaction (GOR) presents an opportunity to produce hydrogen and high-value chemical products. Herein, we investigate the effect of Sn in Ni nanoparticles for the GOR to formic acid (FA). Electrochemical results show that the maximum activity is related to the amount of Ni, as Ni sites are responsible for catalyzing GOR via the NiOOH/Ni(OH)2 pair. However, the GOR kinetics increases with the amount of Sn, associated with an enhancement of the OH- supply to the catalyst surface for Ni(OH)2 reoxidation to NiOOH. NiSn nanoparticles supported on carbon nanotubes (NiSn/CNT) exhibit excellent current densities and direct GOR via C-C cleavage mechanism, obtaining FA with a Faradaic efficiency (FE) of 93% at 1.45 V vs. reversible hydrogen electrode. GOR selectivity is further studied by varying the applied potential, glucose concentration, reaction time, and temperature. FE toward FA production decreases due to formic overoxidation to carbonates at low glucose concentrations and high applied potentials, while acetic and lactic acids are obtained with high selectivity at high glucose concentrations and 55 °C. Density functional theory calculations show that the SnO2 facilitates the adsorption of glucose on the surface of Ni and promotes the formation of the catalytic active Ni3+ species.

Preparation and characterization of carboxymethyl microcrystalline cellulose from pineapple leaf fibre

Highly functional and robust biobased materials are still in research to produce valuable composites for various applications. The literature shows the gap of new raw biobased materials in market which can functionally tuned and structurally modified for development of 2d/3d architectures. Thus, in the present study, very cheap, easily available agricultural waste, pineapple leaf fiber (PL-raw) was used for the isolation of microcrystalline cellulose (PL-MCC) and further functionalized using upscaled chemical approach to carboxymethyl microcrystalline cellulose (PL-CMMCC). Very advanced techniques like Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction analysis (XRD), and differential scanning calorimetry (DSC) served to characterize the raw material, high crystalline PL-MCC, and modified carboxy methyl MCC. FTIR determined presence of different absorbed peak at approximately 1620.2 cm−1, and at 1423.8 cm−1, carboxyl groups were assigned to PL-CMMCC. On the other hand, the XRD findings verified that PL-CMMCC’s crystalline structure has decreased. Analysis by SEM revealed a damaged surface morphology for PL-CMMCC. Following chemical treatments, the EDX analysis revealed that each fiber sample contained a highly pure cellulose elemental composition. Thus, results explain the utilization of agricultural waste, pineapple leaf fiber to high valuable products like highly crystalline PL-MCC, in addition further modification of PL-MCC could leads to formation of highly functional material that could be used for other applications too in future.

Continuous flow versatile conversion of furfural to valuable end products catalyzed by commercial Pd/C

The conversion of furfural has gained significant attention in recent years due to its potential for transforming this basic chemical into a wide range of valuable end products, such as alcohols, amines, acids, and biopolymers. This contribution aims to demonstrate the versatility and potential of continuous flow processes combined with commercial Pd/C catalysts for converting furfural into high value-added chemicals, including furfuryl alcohol, tetrahydrofurfuryl alcohol, and furfurylimine. By optimizing reaction conditions, high product yields (60–90%) were achieved, marking the first literature example of continuous flow conversion of furfural into diverse products, such as alcohols and imines. This work advances the production of high-value products using propanol as a hydrogen donor, with high yields and selectivity, employing commercial catalysts in a scalable continuous process.

Agro-Based nanoparticles composite: A novel approach for enhanced ballistic applications

The field of material science has witnessed a paradigm shift with the emergence of agro-based nanoparticles composites demonstrating remarkable potential for advanced applications. Agricultural by-products, such as cellulose, lignin, and chitin, are selected as the base materials due to their abundance, renewability, low adverse environmental impact and acceptable mechanical properties. The developed composites exhibits superior specific mechanical properties compared to traditional materials. This review explores the synthesis, characterization, and application of agro-based nanoparticles in composites development for ballistic purposes. The eco-friendly nature and synthesis of agro-based composite aligns with the current sustainability goals, offering a green alternative to conventional materials being used in ballistic applications. The utilization of agricultural by-products not only mitigates environmental concerns but also promotes the circular economy by repurposing waste materials into high-value products. This review presents a novel approach in the field of ballistic materials by harnessing the potential of agro-based nanoparticles composites. The superior specific mechanical properties make this composite material a promising candidate for ballistic applications, thereby, opening avenues for sustainable advancements in defense and security technologies. Keywords: Agro-based, Nanoparticles, Composites, Green Technology, Ballistic Application.

Insights into lignin bioconversion: lignin-derived compounds treatment of a novel marine fungus K-2.

The potential for the efficient conversion of lignocellulosic biomass has been extensively explored to produce a wide range of bioproducts. Many approaches have been sought for the deep conversion of lignin to generate products that are toxin-free and beneficial for processing into high-value-added components. This study reported a fungus isolated from the deep sea with strong synthesis of multiple lignocellulases, conversion of lignin and guaiacol (0.1%) by 71.6% and 86.1% within 9 days at 30 °C respectively, and outstanding environmental adaptability (20-50 °C and pH 3-8). Metabolic pathway profiling showed that this fungus utilized lignin to rapidly activate multiple ring-opening reactions including the 2,3- and 3,4-cleavage pathways, with the 2,3-cleavage pathway predominating after 5 days. Conversion of metabolic intermediates confirmed the superb potential of this strain for lignin treatment. Meanwhile, its shikimic acid pathway was metabolically active under lignin. This further expands the potential to produce valuable bioproducts during lignin treatment, especially under ambient conditions, which can significantly enhance high-value precursor compound production. © 2024 Society of Chemical Industry.

Effects of spray drying and freeze drying on the protein profile of whey protein concentrate.

Whey protein concentrate (WPC) is consumed for its high protein content. The structure and biological functionality of whey proteins in WPC powders may be affected by the drying technique applied. However, the specific impact of spray drying and freeze drying on the overall protein profile of whey protein derived from sweet whey streams at scale is unknown. Herein, we examine the effects of commercial-scale freeze drying and spray drying on WPC to determine which method better preserves bioactive whey proteins, with the goal of helping the dairy industry create high-value products that meet the growing consumer demand for functional dairy products. WPCs were produced from pasteurized liquid whey using either a commercial spray dryer or freeze dryer. A variety of analytical techniques, including enzyme-linked immunosorbent assay, polyacrylamide gel electrophoresis, and bottom-up proteomics using liquid chromatography-tandem mass spectroscopy were used to identify, quantify, and compare the retention of bioactive proteins in WPC before and after spray drying and freeze drying. In addition, the extent of denaturation was studied via solubility testing, differential scanning calorimetry, and hydrophobicity assessment. There was little to no difference in the retention or denaturation of key bioactive proteins between spray-dried and freeze-dried WPC powders. There was a higher percentage of select Maillard modifications in freeze-dried and spray-dried powders than in the control. The lack of significant differences between spray drying and freeze drying identified herein indicates that freeze drying does not meaningfully improve retention of bioactive proteins compared with spray drying when performed after multiple pasteurization steps. PRACTICAL APPLICATION: This study aimed to provide insight into the impacts of spray drying versus freeze drying on whey proteins. Overall, our results indicate that for commercial dairy processing that involves multiple rounds of pasteurization, freeze drying does not meaningfully improve the retention of bioactive proteins compared with spray drying. These findings may help the food and dairy industry make informed decisions regarding the processing of its whey protein products to optimize nutritional value.

Effect of calcination temperature on the activity of basalt tailings for the lightweight geopolymer from microwave curing

Basalt, the most widely distributed alumino-silicate volcanic rock on Earth, is commonly utilized in construction aggregate area. The challenge lies in how to utilize the tailings produced during mining processes to create high-value products through energy-efficient and environmentally-friendly means. A previous study has already shown the use of basalt tail powder as raw material for lightweight geopolymer materials supported microwave curing, without an extensive focus on mechanical properties, in turn known to be significantly affected by the reactivity of constituents. Here, calcination operations are discussed in their impact on the activity of basalt for lightweight geopolymer from microwave curing. Additionally, the thermal characteristics of basalt during temperature were analyzed using differential scanning calorimetry, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analyses were employed to examine the micromorphology, chemical structure, phase compositions, and reaction degree of basalt and its alkali activated products. The results prove that basalt is a sustainable raw material for geopolymers, with properties already optimized without calcination, in turn determining a slight increase only at 750 °C (resulting in compressive strength >7 MPa, with a porosity of 30 %). The effect mechanism of calcination temperature on the activity of basalt tailings for the lightweight geopolymer from microwave curing is also discussed.

Ag Nanoparticles-Confined Doped within Triazine-Based Covalent Organic Frameworks for Syngas Production from Electrocatalytic Reduction of CO2.

Electrocatalytic CO2 reduction reaction (CO2RR) emerges as a promising avenue to mitigate carbon emissions, enabling the capture and conversion of CO2 into high-value products such as syngas with CO/H2. One of the crucial aspects lies in the tailored development of durable and efficient electrocatalysts for the CO2RR. Covalent organic frameworks (COFs) possess unique characteristics that render them attractive candidates for catalytic applications. However, the relationship between structure and performance still requires further exploration; especially, most COFs with such properties are limited to COFs containing specific groups such as phthalocyanine or porphyrin groups. Here, we custom-synthesize two azine-linked nitrogen-rich COFs constructed from triazine building blocks, which are doped with ultrafine and highly dispersed Ag nanoparticles (Ag@TFPT-HZ and Ag@TPT-HZ). Thus-obtained COFs can serve as electrocatalysts for the CO2RR, and a comprehensive investigation has been conducted to uncover the intricate structure-performance relationship within these materials. Notably, Ag@TFPT-HZ exhibits superior CO selectivity in the electrocatalytic CO2RR, achieving a FECO of 81% and a partial current density of 7.65 mA·cm-2 at the potential of -1.0 V (vs reversible hydrogen electrode (RHE)). In addition, Ag@TPT-HZ as an electrocatalyst can continuously produce syngas with a CO/H2 molar ratio of 1:1, an ideal condition for methanol synthesis. The observed distinct performance between these two COFs is attributed to the presence of O atoms in TFPT-HZ. These O atoms facilitate a higher loading capacity of Ag nanoparticles (11 wt %) and generate a greater number of active sites, thereby enhancing electrochemical activity and promoting faster reaction kinetics. Therefore, two tailor-made two-dimensional (2D) nitrogen-rich COFs with various active sites as electrocatalysts can exhibit different outstanding electrocatalytic performances for CO2RR and possess high cycling stability (>50 h). This work offers valuable insights into the design and synthesis of electrocatalysts, particularly in elucidating the intricate relationship between their structure and performance.