AI 中文总结
该研究通过第一性原理方法，发现配体官能化和pH调控可优化MOF-5的带隙与还原能量学，其中COOH官能化结合Sr/Ba节点的架构是可见光下CO₂还原的最优方案。
AI 中文摘要
金属有机框架（MOF）-5具有高孔隙率和良好的传质特性，但其宽带隙限制了其在光催化二氧化碳（CO₂）还原中的应用。采用最先进的第一性原理方法，我们系统研究了体积应变、金属节点取代、配体官能化和pH控制作为调控旋钮对提升MOF-5的CO₂光催化能力的影响。应变和金属节点取代对带隙的影响可忽略不计，而配体官能化通过在带隙中引入态将带隙缩小至可见光范围，同时在pH=0时保持还原侧的能级对齐。由此产生的还原能量学对配体官能化和pH均高度敏感。在碱性条件下，卤化和羟基化的框架主要生成HCOOH、CO和HCHO，主要使用Mg和Zn节点；而COOH官能化在整个CO₂还原序列中提供了最广泛的热力学可达性。NH₂官能化保留了所有目标还原路径的热力学可行性，但具有更大的过电位；NO₂官能化通常产生不利的还原能量学。关键的是，在COOH系列中，金属节点的选择可将基本带隙调控超过1 eV，而过电位的变化极小，这使得基于Sr和Ba的架构成为可见光激发下具有最宽产物选择性的最有利体系。配体官能化显著降低了前线态的空间重叠，促进了光生电荷分离。综合来看，这些结果确立了配体官能化和溶液pH作为互补的设计杠杆，可独立调控MOF-5的光吸收和CO₂还原能量学，为设计高效的MOF基光催化剂建立了合理且可行的途径。
英文摘要
The wide band gap of metal-organic framework (MOF) 5 constrains its use in photocatalytic carbon dioxide (CO$_2$) reduction despite its high porosity and favorable mass-transport properties. Adopting a state-of-the-art first-principles approach, we systematically investigate the effects of volumetric strain, metal-node substitution, linker functionalization, and pH control as knobs to improve the CO$_2$ photocatalytic ability of MOF-5. Strain and metal-node substitution negligibly affect the gap, whereas linker functionalization narrows it into the visible range via in-gap states while preserving reduction-side alignment at pH = 0. The resulting reduction energetics are strongly sensitive to both linker functionalization and pH. Halogenated and hydroxylated frameworks provide access primarily to HCOOH, CO, and HCHO under alkaline conditions, principally with the Mg and Zn nodes, whereas COOH functionalization offers the broadest thermodynamic accessibility across the full CO$_2$ reduction sequence. NH$_2$ retains thermodynamic feasibility for all target reduction pathways but with larger overpotentials, while NO$_2$ generally yields unfavorable reduction energetics. Crucially, within the COOH series, the choice of the metal node tunes the fundamental gap by over 1 eV with only minor changes in the reduction overpotentials, placing Sr- and Ba-based architectures as the most favorable ones for broad product selectivity with visible-light excitation. Linker functionalization substantially reduces the spatial overlap of the frontier states, promoting photoinduced charge separation. Taken together, these results establish linker functionalization and solution pH as complementary design levers for independently tuning light absorption and CO$_2$-reduction energetics in MOF-5, establishing a rational and viable route for designing efficient MOF-based photocatalysts.
