Addition of small amounts of water to the organic solvent may result in different promoting or inhibiting effects in aldol condensation reactions depending on the distribution of active sites on the surface. In a combination of liquid-phase catalytic activity measurements, spectroscopies, and theoretical calculations, we have shown that water clusters around the acid site can form bridges with a ketone molecule located close to the activated carbonyl on another site. When the distance between the two acid sites is greater than a distance corresponding to about two water molecules, the efficiency of the bond polarization of the ketone by a remotely located acid site decreases significantly, and the presence of water no longer promotes the reaction. This work provides a quantitative assessment of how solvent molecules can bridge isolated active sites to enable cooperative catalysis, which offers an additional dimension for engineering catalysis at the nanoscale.

根据表面活性位点的分布，向有机溶剂中加入少量的水可能会导致羟醛缩合反应产生不同的促进或抑制作用。在液相催化活性测量、光谱学和理论计算的组合中，我们已经表明，酸位点周围的水团簇可以与另一个位点上靠近活性羰基的酮分子形成桥。当两个酸位之间的距离大于对应于大约两个水分子的距离时，位于远处的酸位对酮的键极化效率显着降低，并且水的存在不再促进反应。