Highly stableβ‑ketoenamine‑based covalent organic frameworks(COFs):synthesis and optoelectrical applications

Covalent organic frameworks(COFs)are one class of porous materials with permanent porosity and regular channels,and have a covalent bond structure.Due to their interesting characteristics,COFs have exhibited diverse potential applications in many felds.However,some applications require the frameworks to possess high structural stability,excellent crystallinity,and suitable pore size.COFs based onβ-ketoenamine and imines are prepared through the irreversible enol-to-keto tautomerization.These materials have high crystallinity and exhibit high stability in boiling water,with strong resistance to acids and bases,resulting in various possible applications.In this review,we frst summarize the preparation methods for COFs based onβ-ketoenamine,in the form of powders,flms and foams.Then,the efects of diferent synthetic methods on the crystallinity and pore structure of COFs based onβ-ketoenamine are analyzed and compared.The relationship between structures and diferent applications including fuorescence sensors,energy storage,photocatalysis,electrocatalysis,batteries and proton conduction are carefully summarized.Finally,the potential applications,large-scale industrial preparation and challenges in the future are presented.

单元式双钢板组合剪力墙抗侧性能影响因素分析

单元式双钢板混凝土组合剪力墙是一种新型的双钢板混凝土组合剪力墙,主要构造是墙体上下的边缘梁与墙单元利用螺栓进行连接。墙体单元在工厂预制,整片墙体在施工现场全螺栓装配。因此该新型双钢板混凝土组合剪力墙施工方便快捷、便于组合拆装,可以实现建筑物生命周期结束后的全更换,既绿色环保又节省成本。在此基础上,对此新型双钢板混凝土组合剪力墙的抗侧力学性能进行了基本分析。首先结合箱型双钢板组合剪力墙的抗剪性能试验研究,建立了ABAQUS有限元模型进行验证,论证了所建立的ABAQUS模型的可靠性。然后建立了23个单元式双钢板混凝土组合剪力墙的有限元模型,研究了墙体分割单元数量、混凝土抗压强度、钢材屈服强度、轴压比和钢板厚度对其抗侧承载力、抗侧刚度和延性等基本力学性能的影响。1)墙体单元数量的变化范围为1~4,随着墙体单元数量的增多,墙体屈服荷载及峰值荷载均降低,墙体的总承载能力逐渐降低;墙体的极限位移逐渐增大,延性系数越来越大,变形能力有所提高。2)混凝土抗压强度的变化范围为30~80 MPa,随着混凝土强度的提高,墙体的抗侧刚度略有提高,极限位移基本呈现减小的趋势,墙体的延性系数逐步减小,衰减幅度较小。墙体的变形能力逐渐降低,但减幅并不大。3)钢板屈服强度的变化范围为235~500 MPa,随着钢板屈服强度的增大,墙体的屈服荷载和峰值荷载逐渐增加,承载能力有所增加;墙体的屈服位移及极限位移逐渐增加,墙体的延性系数逐渐增加,变形能力有所提高。4)轴压比的变化范围为0.1~0.6,每级增加0.1,在轴压比较小时,提高轴压比能够提高组合剪力墙的屈服荷载及峰值荷载。5)钢板厚度的变化范围为2~6 mm,随着钢板厚度的增大,墙体的屈服荷载和峰值荷载逐渐增加,承载能力有所增加,墙体的初始抗侧刚度和延性系数逐渐增加,变形能力有所提高。通过分析可以得到:增大混凝土强度、钢板屈服强度、钢板厚度能够提高承载力,另外,提升钢板屈服强度和钢板厚度均会提高其延性;单元式双钢板组合剪力墙在水平荷载作用下的抗侧刚度由混凝土部分和钢板两部分共同贡献,增大钢板厚度能够提高其抗侧刚度;墙体单元数量越多,其初始刚度越小,承载力降低。建议在满足施工环境的条件下,两个相邻框架柱之间墙体的单元数量不宜超过3。